diff --git a/compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JSCompilerArguments.kt b/compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JSCompilerArguments.kt
index 0d9d47b1d44..4e2720faa09 100644
--- a/compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JSCompilerArguments.kt
+++ b/compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JSCompilerArguments.kt
@@ -657,6 +657,13 @@ class K2JSCompilerArguments : CommonCompilerArguments() {
         collector.deprecationWarn(irBaseClassInMetadata, false, "-Xir-base-class-in-metadata")
         collector.deprecationWarn(irNewIr2Js, true, "-Xir-new-ir2js")
 
+        if (irPerFile && moduleKind != MODULE_ES) {
+            collector.report(
+                CompilerMessageSeverity.ERROR,
+                "Per-file compilation can't be used with any `moduleKind` except `es` (ECMAScript Modules)"
+            )
+        }
+
         return super.configureAnalysisFlags(collector, languageVersion).also {
             it[allowFullyQualifiedNameInKClass] = wasm && wasmKClassFqn //Only enabled WASM BE supports this flag
         }
diff --git a/compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JsArgumentConstants.java b/compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JsArgumentConstants.java
index 376a33f5a4d..770d438a5f8 100644
--- a/compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JsArgumentConstants.java
+++ b/compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JsArgumentConstants.java
@@ -26,6 +26,10 @@ public interface K2JsArgumentConstants {
     String MODULE_UMD = "umd";
     String MODULE_ES = "es";
 
+    String GRANULARITY_WHOLE_PROGRAM = "whole-program";
+    String GRANULARITY_PER_MODULE = "per-module";
+    String GRANULARITY_PER_FILE = "per-file";
+
     String SOURCE_MAP_SOURCE_CONTENT_ALWAYS = "always";
     String SOURCE_MAP_SOURCE_CONTENT_NEVER = "never";
     String SOURCE_MAP_SOURCE_CONTENT_INLINING = "inlining";
diff --git a/compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt b/compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt
index c089f361435..58b9f3d1589 100644
--- a/compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt
+++ b/compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt
@@ -41,13 +41,9 @@ import org.jetbrains.kotlin.incremental.js.IncrementalDataProvider
 import org.jetbrains.kotlin.incremental.js.IncrementalNextRoundChecker
 import org.jetbrains.kotlin.incremental.js.IncrementalResultsConsumer
 import org.jetbrains.kotlin.ir.backend.js.*
-import org.jetbrains.kotlin.ir.backend.js.codegen.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.dce.dumpDeclarationIrSizesIfNeed
 import org.jetbrains.kotlin.ir.backend.js.ic.*
-import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.CompilationOutputsBuilt
-import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.IrModuleToJsTransformer
-import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsCodeGenerator
-import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.TranslationMode
+import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.*
 import org.jetbrains.kotlin.ir.declarations.impl.IrFactoryImpl
 import org.jetbrains.kotlin.ir.declarations.impl.IrFactoryImplForJsIC
 import org.jetbrains.kotlin.ir.linkage.partial.setupPartialLinkageConfig
@@ -71,8 +67,8 @@ import java.io.IOException
 
 private val K2JSCompilerArguments.granularity: JsGenerationGranularity
     get() = when {
-        this.irPerModule -> JsGenerationGranularity.PER_MODULE
         this.irPerFile -> JsGenerationGranularity.PER_FILE
+        this.irPerModule -> JsGenerationGranularity.PER_MODULE
         else -> JsGenerationGranularity.WHOLE_PROGRAM
     }
 
@@ -129,7 +125,7 @@ class K2JsIrCompiler : CLICompiler<K2JSCompilerArguments>() {
             val ir = lowerIr()
             val transformer = IrModuleToJsTransformer(ir.context, mainCallArguments, ir.moduleFragmentToUniqueName)
 
-            val mode = TranslationMode.fromFlags(arguments.irDce, arguments.irPerModule, arguments.irMinimizedMemberNames)
+            val mode = TranslationMode.fromFlags(arguments.irDce, arguments.granularity, arguments.irMinimizedMemberNames)
             return transformer.makeJsCodeGenerator(ir.allModules, mode)
         }
 
@@ -303,7 +299,7 @@ class K2JsIrCompiler : CLICompiler<K2JSCompilerArguments>() {
                     relativeRequirePath = true
                 )
 
-                val (outputs, rebuiltModules) = jsExecutableProducer.buildExecutable(arguments.irPerModule, outJsProgram = false)
+                val (outputs, rebuiltModules) = jsExecutableProducer.buildExecutable(arguments.granularity, outJsProgram = false)
                 outputs.writeAll(outputDir, outputName, arguments.generateDts, moduleName, moduleKind)
 
                 icCaches.cacheGuard.release()
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
index 1b6a8dcbe7a..ef9d1de58e3 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
@@ -22,9 +22,9 @@ import org.jetbrains.kotlin.ir.IrBuiltIns
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
-import org.jetbrains.kotlin.ir.backend.js.codegen.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.ir.JsIrBuilder
 import org.jetbrains.kotlin.ir.backend.js.lower.JsInnerClassesSupport
+import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsPolyfills
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.translateJsCodeIntoStatementList
 import org.jetbrains.kotlin.ir.backend.js.utils.*
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
index 6e52dd5f6d7..bce143f297b 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
@@ -16,7 +16,6 @@ import org.jetbrains.kotlin.backend.common.lower.inline.LocalClassesInInlineLamb
 import org.jetbrains.kotlin.backend.common.lower.loops.ForLoopsLowering
 import org.jetbrains.kotlin.backend.common.lower.optimizations.FoldConstantLowering
 import org.jetbrains.kotlin.backend.common.phaser.*
-import org.jetbrains.kotlin.ir.backend.js.codegen.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.lower.*
 import org.jetbrains.kotlin.ir.backend.js.lower.calls.CallsLowering
 import org.jetbrains.kotlin.ir.backend.js.lower.cleanup.CleanupLowering
@@ -24,6 +23,7 @@ import org.jetbrains.kotlin.ir.backend.js.lower.coroutines.AddContinuationToFunc
 import org.jetbrains.kotlin.ir.backend.js.lower.coroutines.JsSuspendArityStoreLowering
 import org.jetbrains.kotlin.ir.backend.js.lower.coroutines.JsSuspendFunctionsLowering
 import org.jetbrains.kotlin.ir.backend.js.lower.inline.*
+import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.declarations.IrFile
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
 
@@ -840,15 +840,6 @@ private val cleanupLoweringPhase = makeBodyLoweringPhase(
     description = "Clean up IR before codegen"
 )
 
-private val moveOpenClassesToSeparatePlaceLowering = makeCustomJsModulePhase(
-    { context, module ->
-        if (context.granularity == JsGenerationGranularity.PER_FILE)
-            moveOpenClassesToSeparateFiles(module)
-    },
-    name = "MoveOpenClassesToSeparateFiles",
-    description = "Move open classes to separate files"
-).toModuleLowering()
-
 private val jsSuspendArityStorePhase = makeDeclarationTransformerPhase(
     ::JsSuspendArityStoreLowering,
     name = "JsSuspendArityStoreLowering",
@@ -962,7 +953,6 @@ val loweringList = listOf<Lowering>(
     cleanupLoweringPhase,
     // Currently broken due to static members lowering making single-open-class
     // files non-recognizable as single-class files
-    // moveOpenClassesToSeparatePlaceLowering,
     validateIrAfterLowering,
 )
 
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsMapping.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsMapping.kt
index f5d3acf9cc9..83f4ad592f2 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsMapping.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsMapping.kt
@@ -9,11 +9,15 @@ import org.jetbrains.kotlin.backend.common.DefaultDelegateFactory
 import org.jetbrains.kotlin.backend.common.DefaultMapping
 import org.jetbrains.kotlin.ir.backend.js.utils.MutableReference
 import org.jetbrains.kotlin.ir.declarations.*
+import java.util.WeakHashMap
 
 class JsMapping : DefaultMapping() {
     val esClassWhichNeedBoxParameters = DefaultDelegateFactory.newDeclarationToValueMapping<IrClass, Boolean>()
     val esClassToPossibilityForOptimization = DefaultDelegateFactory.newDeclarationToValueMapping<IrClass, MutableReference<Boolean>>()
 
+    // Check if we need concurrency here
+    val chunkToOriginalFile = WeakHashMap<IrFile, IrFile>()
+
     val outerThisFieldSymbols = DefaultDelegateFactory.newDeclarationToDeclarationMapping<IrClass, IrField>()
     val innerClassConstructors = DefaultDelegateFactory.newDeclarationToDeclarationMapping<IrConstructor, IrConstructor>()
     val originalInnerClassPrimaryConstructorByClass = DefaultDelegateFactory.newDeclarationToDeclarationMapping<IrClass, IrConstructor>()
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/codegen/JsGenerationGranularity.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/codegen/JsGenerationGranularity.kt
deleted file mode 100644
index 15badb9851e..00000000000
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/codegen/JsGenerationGranularity.kt
+++ /dev/null
@@ -1,12 +0,0 @@
-/*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.ir.backend.js.codegen
-
-enum class JsGenerationGranularity {
-    WHOLE_PROGRAM,
-    PER_MODULE,
-    PER_FILE
-}
\ No newline at end of file
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compiler.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compiler.kt
index 1a3ba942949..a94ff4609b2 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compiler.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compiler.kt
@@ -10,12 +10,12 @@ import org.jetbrains.kotlin.backend.common.phaser.PhaseConfig
 import org.jetbrains.kotlin.backend.common.phaser.invokeToplevel
 import org.jetbrains.kotlin.config.CompilerConfiguration
 import org.jetbrains.kotlin.ir.IrBuiltIns
-import org.jetbrains.kotlin.ir.backend.js.codegen.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.lower.collectNativeImplementations
 import org.jetbrains.kotlin.ir.backend.js.lower.generateJsTests
 import org.jetbrains.kotlin.ir.backend.js.lower.moveBodilessDeclarationsToSeparatePlace
 import org.jetbrains.kotlin.ir.backend.js.lower.serialization.ir.JsIrLinker
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.CompilationOutputs
+import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.TranslationMode
 import org.jetbrains.kotlin.ir.declarations.IrFactory
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compilerWithIC.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compilerWithIC.kt
index 4d660a81633..1cda7badde2 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compilerWithIC.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compilerWithIC.kt
@@ -9,7 +9,6 @@ import org.jetbrains.kotlin.backend.common.phaser.PhaseConfig
 import org.jetbrains.kotlin.backend.common.phaser.PhaserState
 import org.jetbrains.kotlin.config.CompilerConfiguration
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
-import org.jetbrains.kotlin.ir.backend.js.codegen.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.ic.JsIrCompilerICInterface
 import org.jetbrains.kotlin.ir.backend.js.lower.collectNativeImplementations
 import org.jetbrains.kotlin.ir.backend.js.lower.generateJsTests
@@ -53,7 +52,7 @@ class JsIrCompilerWithIC(
         allModules: Collection<IrModuleFragment>,
         dirtyFiles: Collection<IrFile>,
         mainArguments: List<String>?
-    ): List<() -> JsIrProgramFragment> {
+    ): List<() -> List<JsIrProgramFragment>> {
         val shouldGeneratePolyfills = context.configuration.getBoolean(JSConfigurationKeys.GENERATE_POLYFILLS)
 
         allModules.forEach {
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/JsUsefulDeclarationProcessor.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/JsUsefulDeclarationProcessor.kt
index 279b92f5d9c..02511255b40 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/JsUsefulDeclarationProcessor.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/JsUsefulDeclarationProcessor.kt
@@ -159,7 +159,7 @@ internal class JsUsefulDeclarationProcessor(
             context.intrinsics.jsPrototypeOfSymbol.owner.enqueue(irClass, "interface default implementation")
         }
 
-        if ((!context.es6mode || !isEsModules) && (irClass.isInner || irClass.isObject)) {
+        if (irClass.isInner || irClass.isObject) {
             context.intrinsics.jsDefinePropertySymbol.owner.enqueue(irClass, "object lazy initialization")
         }
 
@@ -185,8 +185,6 @@ internal class JsUsefulDeclarationProcessor(
             irFunction.parentClassOrNull?.takeIf { it.isInterface }?.enqueue(irFunction, "interface default method is used")
         }
 
-        if (context.es6mode && isEsModules) return
-
         val property = irFunction.correspondingPropertySymbol?.owner ?: return
 
         if (property.isExported(context) || property.getJsName() != null || property.isOverriddenExternal()) {
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/export/ExportModelToJsStatements.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/export/ExportModelToJsStatements.kt
index 6de4b2eca12..48155007c8a 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/export/ExportModelToJsStatements.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/export/ExportModelToJsStatements.kt
@@ -93,16 +93,11 @@ class ExportModelToJsStatements(
 
             is ExportedProperty -> {
                 require(namespace != null || esModules) { "Only namespaced properties are allowed" }
-                when {
-                    namespace == null -> {
+                when (namespace) {
+                    null -> {
                         val property = declaration.generateTopLevelGetters()
                         listOf(JsVars(property), JsExport(property.name.makeRef(), JsName(declaration.name, false)))
                     }
-                    es6mode && declaration.isMember -> {
-                        val jsClass = parentClass?.getCorrespondingJsClass() ?: error("Expect to have parentClass at this point")
-                        jsClass.members += declaration.generateClassMembers()
-                        listOf(JsEmpty)
-                    }
                     else -> {
                         val getter = declaration.irGetter?.let { staticContext.getNameForStaticDeclaration(it) }
                         val setter = declaration.irSetter?.let { staticContext.getNameForStaticDeclaration(it) }
@@ -123,10 +118,11 @@ class ExportModelToJsStatements(
 
             is ExportedObject -> {
                 require(namespace != null || esModules) { "Only namespaced properties are allowed" }
+                val (name, objectClassInitialization) = declaration.getNameAndInitialization()
                 val newNameSpace = when {
                     namespace != null -> jsElementAccess(declaration.name, namespace)
                     else ->
-                        jsElementAccess(Namer.PROTOTYPE_NAME, staticContext.getNameForClass(declaration.ir).makeRef())
+                        jsElementAccess(Namer.PROTOTYPE_NAME, name.makeRef())
                 }
                 val staticsExport =
                     declaration.nestedClasses.flatMap { generateDeclarationExport(it, newNameSpace, esModules, declaration.ir) }
@@ -155,19 +151,19 @@ class ExportModelToJsStatements(
                     )
                 }
 
-                objectExport + staticsExport
+                listOfNotNull(objectClassInitialization.takeIf { staticsExport.isNotEmpty() }) + objectExport + staticsExport
             }
 
             is ExportedRegularClass -> {
                 if (declaration.isInterface) return emptyList()
-                val name = staticContext.getNameForStaticDeclaration(declaration.ir)
+                val (name, classInitialization) = declaration.getNameAndInitialization()
                 val newNameSpace = when {
                     namespace != null -> jsElementAccess(declaration.name, namespace)
                     esModules -> name.makeRef()
-                    else -> prototypeOf(staticContext.getNameForClass(declaration.ir).makeRef(), staticContext)
+                    else -> prototypeOf(name.makeRef(), staticContext)
                 }
                 val klassExport = when {
-                    namespace != null -> jsAssignment(newNameSpace, JsNameRef(name)).makeStmt()
+                    namespace != null -> jsAssignment(newNameSpace, name.makeRef()).makeStmt()
                     esModules -> JsExport(name.makeRef(), alias = JsName(declaration.name, false))
                     else -> null
                 }
@@ -181,12 +177,12 @@ class ExportModelToJsStatements(
 
                 val innerClassesAssignments = declaration.nestedClasses
                     .filter { it.ir.isInner }
-                    .map { it.generateInnerClassAssignment(declaration) }
+                    .map { it.generateInnerClassAssignment(name) }
 
                 val staticsExport = (staticFunctions + enumEntries + declaration.nestedClasses)
                     .flatMap { generateDeclarationExport(it, newNameSpace, esModules, declaration.ir) }
 
-                listOfNotNull(klassExport) + staticsExport + innerClassesAssignments
+                listOfNotNull(classInitialization, klassExport) + staticsExport + innerClassesAssignments
             }
         }
     }
@@ -210,43 +206,9 @@ class ExportModelToJsStatements(
         )
     }
 
-    private fun ExportedProperty.generateClassMembers(): List<JsFunction> {
-        val getter = irGetter?.let { staticContext.getNameForStaticDeclaration(it) }
-        val setter = irSetter?.let { staticContext.getNameForStaticDeclaration(it) }
-
-        return buildList {
-            if (getter != null) {
-                add(JsFunction(emptyScope, "").also {
-                    it.name = JsName(name, false)
-                    if (isStatic) {
-                        it.modifiers.add(JsFunction.Modifier.STATIC)
-                    }
-                    it.modifiers.add(JsFunction.Modifier.GET)
-                    it.body = JsBlock().apply {
-                        statements.add(JsReturn(JsInvocation(getter.makeRef())))
-                    }
-                })
-            }
-            if (setter != null) {
-                add(JsFunction(emptyScope, "").also {
-                    val value = JsName("value", true)
-                    it.name = JsName(name, false)
-                    it.parameters.add(JsParameter(value))
-                    if (isStatic) {
-                        it.modifiers.add(JsFunction.Modifier.STATIC)
-                    }
-                    it.modifiers.add(JsFunction.Modifier.SET)
-                    it.body = JsBlock().apply {
-                        statements.add(JsExpressionStatement(JsInvocation(setter.makeRef(), value.makeRef())))
-                    }
-                })
-            }
-        }
-    }
-
-    private fun ExportedClass.generateInnerClassAssignment(outerClass: ExportedClass): JsStatement {
-        val innerClassRef = staticContext.getNameForStaticDeclaration(ir).makeRef()
-        val outerClassRef = staticContext.getNameForStaticDeclaration(outerClass.ir).makeRef()
+    private fun ExportedClass.generateInnerClassAssignment(outerClassName: JsName): JsStatement {
+        val innerClassRef = ir.getClassRef(staticContext)
+        val outerClassRef = outerClassName.makeRef()
         val companionObject = ir.companionObject()
         val secondaryConstructors = members.filterIsInstanceAnd<ExportedFunction> { it.isStatic }
         val bindConstructor = JsName("__bind_constructor_", false)
@@ -283,30 +245,27 @@ class ExportModelToJsStatements(
         blockStatements.add(JsReturn(bindConstructor.makeRef()))
         val innerClassGetter = JsFunction(emptyScope, JsBlock(*blockStatements.toTypedArray()), "inner class '$name' getter")
 
-        return if (es6mode) {
-            outerClass.ir.getCorrespondingJsClass().members += innerClassGetter.also {
-                it.name = JsName(name, false)
-                it.modifiers.add(JsFunction.Modifier.GET)
+        return defineProperty(
+            prototypeOf(outerClassRef, staticContext),
+            name,
+            innerClassGetter,
+            null,
+            staticContext
+        ).makeStmt()
+    }
+
+    private fun ExportedClass.getNameAndInitialization(): Pair<JsName, JsStatement?> {
+        return when (val classRef = ir.getClassRef(staticContext)) {
+            !is JsNameRef -> {
+                val stableName = JsName(name, true)
+                stableName to JsVars(JsVars.JsVar(stableName, classRef))
             }
-            JsEmpty
-        } else {
-            defineProperty(
-                prototypeOf(outerClassRef, staticContext),
-                name,
-                innerClassGetter,
-                null,
-                staticContext
-            ).makeStmt()
+            else -> classRef.name!! to null
         }
     }
 
-    private fun IrClass.getCorrespondingJsClass(): JsClass {
-        val jsClassModel = staticContext.classModels[symbol] ?: error("Class with name '$name' was not found")
-        return (jsClassModel.preDeclarationBlock.statements.first() as? JsExpressionStatement)?.expression as? JsClass
-            ?: error("Expect to have JsClass as a first statement inside JsIrClassModel")
-    }
 
-    private fun JsNameRef.bindToThis(bindTo: JsExpression): JsInvocation {
+    private fun JsExpression.bindToThis(bindTo: JsExpression): JsInvocation {
         return JsInvocation(JsNameRef("bind", this), bindTo, JsThisRef())
     }
 }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/CacheUpdater.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/CacheUpdater.kt
index b3a99dd6b69..5083fd43e67 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/CacheUpdater.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/CacheUpdater.kt
@@ -10,7 +10,7 @@ import org.jetbrains.kotlin.backend.common.serialization.IrInterningService
 import org.jetbrains.kotlin.backend.common.serialization.cityHash64
 import org.jetbrains.kotlin.config.CompilerConfiguration
 import org.jetbrains.kotlin.ir.backend.js.*
-import org.jetbrains.kotlin.ir.backend.js.codegen.JsGenerationGranularity
+import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsIrProgramFragment
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.util.*
@@ -33,7 +33,7 @@ fun interface JsIrCompilerICInterface {
         allModules: Collection<IrModuleFragment>,
         dirtyFiles: Collection<IrFile>,
         mainArguments: List<String>?
-    ): List<() -> JsIrProgramFragment>
+    ): List<() -> List<JsIrProgramFragment>>
 }
 
 fun interface JsIrCompilerICInterfaceFactory {
@@ -616,7 +616,7 @@ class CacheUpdater(
     private fun commitCacheAndBuildModuleArtifacts(
         incrementalCacheArtifacts: Map<KotlinLibraryFile, IncrementalCacheArtifact>,
         moduleNames: Map<KotlinLibraryFile, String>,
-        rebuiltFileFragments: KotlinSourceFileMap<JsIrProgramFragment>
+        rebuiltFileFragments: KotlinSourceFileMap<List<JsIrProgramFragment>>
     ): List<ModuleArtifact> = stopwatch.measure("Incremental cache - committing artifacts") {
         incrementalCacheArtifacts.map { (libFile, incrementalCacheArtifact) ->
             incrementalCacheArtifact.buildModuleArtifactAndCommitCache(
@@ -630,7 +630,7 @@ class CacheUpdater(
         compilerForIC: JsIrCompilerICInterface,
         loadedFragments: Map<KotlinLibraryFile, IrModuleFragment>,
         dirtyFiles: Map<KotlinLibraryFile, Set<KotlinSourceFile>>
-    ): MutableList<Triple<KotlinLibraryFile, KotlinSourceFile, () -> JsIrProgramFragment>> =
+    ): MutableList<Triple<KotlinLibraryFile, KotlinSourceFile, () -> List<JsIrProgramFragment>>> =
         stopwatch.measure("Processing IR - lowering") {
             val dirtyFilesForCompiling = mutableListOf<IrFile>()
             val dirtyFilesForRestoring = mutableListOf<Pair<KotlinLibraryFile, KotlinSourceFile>>()
@@ -737,7 +737,7 @@ class CacheUpdater(
     private data class FragmentGenerators(
         val incrementalCacheArtifacts: Map<KotlinLibraryFile, IncrementalCacheArtifact>,
         val moduleNames: Map<KotlinLibraryFile, String>,
-        val generators: MutableList<Triple<KotlinLibraryFile, KotlinSourceFile, () -> JsIrProgramFragment>>
+        val generators: MutableList<Triple<KotlinLibraryFile, KotlinSourceFile, () -> List<JsIrProgramFragment>>>
     )
 
     private fun loadIrAndMakeIrFragmentGenerators(): FragmentGenerators {
@@ -751,9 +751,9 @@ class CacheUpdater(
     }
 
     private fun generateIrFragments(
-        generators: MutableList<Triple<KotlinLibraryFile, KotlinSourceFile, () -> JsIrProgramFragment>>
-    ): KotlinSourceFileMap<JsIrProgramFragment> = stopwatch.measure("Processing IR - generating program fragments") {
-        val rebuiltFragments = KotlinSourceFileMutableMap<JsIrProgramFragment>()
+        generators: MutableList<Triple<KotlinLibraryFile, KotlinSourceFile, () -> List<JsIrProgramFragment>>>
+    ): KotlinSourceFileMap<List<JsIrProgramFragment>> = stopwatch.measure("Processing IR - generating program fragments") {
+        val rebuiltFragments = KotlinSourceFileMutableMap<List<JsIrProgramFragment>>()
         while (generators.isNotEmpty()) {
             val (libFile, srcFile, fragmentGenerator) = generators.removeFirst()
             rebuiltFragments[libFile, srcFile] = fragmentGenerator()
@@ -783,7 +783,7 @@ fun rebuildCacheForDirtyFiles(
     exportedDeclarations: Set<FqName>,
     mainArguments: List<String>?,
     es6mode: Boolean
-): Pair<IrModuleFragment, List<Pair<IrFile, JsIrProgramFragment>>> {
+): Pair<IrModuleFragment, List<Pair<IrFile, List<JsIrProgramFragment>>>> {
     val internationService = IrInterningService()
     val emptyMetadata = object : KotlinSourceFileExports() {
         override val inverseDependencies = KotlinSourceFileMap<Set<IdSignature>>(emptyMap())
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/HashCalculatorForIC.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/HashCalculatorForIC.kt
index a365f999deb..4488e6551c6 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/HashCalculatorForIC.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/HashCalculatorForIC.kt
@@ -211,7 +211,7 @@ internal fun CrossModuleReferences.crossModuleReferencesHashForIC() = HashCalcul
         update(importedModule.relativeRequirePath ?: "")
     }
 
-    updateForEach(transitiveJsExportFrom) { transitiveExport ->
+    updateForEach(transitiveExportFrom) { transitiveExport ->
         update(transitiveExport.internalName.toString())
         update(transitiveExport.externalName)
     }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/ICUtils.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/ICUtils.kt
index e851e893691..835a71a1ecf 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/ICUtils.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/ICUtils.kt
@@ -32,6 +32,17 @@ internal inline fun File.useCodedOutput(f: CodedOutputStream.() -> Unit) {
     outputStream().useCodedOutput(f)
 }
 
+internal inline fun <T> CodedOutputStream.ifNotNull(value: T?, write: (T) -> Unit) {
+    writeBoolNoTag(value != null)
+    if (value != null) {
+        write(value)
+    }
+}
+
+internal inline fun <T> CodedInputStream.ifTrue(then: () -> T): T? {
+    return if (readBool()) then() else null
+}
+
 internal fun icError(what: String, libFile: KotlinLibraryFile? = null, srcFile: KotlinSourceFile? = null): Nothing {
     val filePath = listOfNotNull(libFile?.path, srcFile?.path).joinToString(":") { File(it).name }
     val msg = if (filePath.isEmpty()) what else "$what for $filePath"
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/IncrementalCacheArtifact.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/IncrementalCacheArtifact.kt
index cda8c9fb9ff..a7cc5f58281 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/IncrementalCacheArtifact.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/IncrementalCacheArtifact.kt
@@ -15,10 +15,10 @@ import java.io.File
 internal sealed class SourceFileCacheArtifact(val srcFile: KotlinSourceFile, val binaryAstFile: File) {
     abstract fun commitMetadata()
 
-    fun commitBinaryAst(fragment: JsIrProgramFragment) {
+    fun commitBinaryAst(fragments: List<JsIrProgramFragment>) {
         binaryAstFile.parentFile?.mkdirs()
         BufferedOutputStream(binaryAstFile.outputStream()).use {
-            fragment.serializeTo(it)
+            fragments.serializeTo(it)
         }
     }
 
@@ -59,7 +59,7 @@ internal class IncrementalCacheArtifact(
 
     fun buildModuleArtifactAndCommitCache(
         moduleName: String,
-        rebuiltFileFragments: Map<KotlinSourceFile, JsIrProgramFragment>,
+        rebuiltFileFragments: Map<KotlinSourceFile, List<JsIrProgramFragment>>,
     ): ModuleArtifact {
         val fileArtifacts = srcCacheActions.map { srcFileAction ->
             val rebuiltFileFragment = rebuiltFileFragments[srcFileAction.srcFile]
@@ -67,7 +67,7 @@ internal class IncrementalCacheArtifact(
                 srcFileAction.commitBinaryAst(rebuiltFileFragment)
             }
             srcFileAction.commitMetadata()
-            SrcFileArtifact(srcFileAction.srcFile.path, rebuiltFileFragment, srcFileAction.binaryAstFile)
+            SrcFileArtifact(srcFileAction.srcFile.path, rebuiltFileFragment ?: emptyList(), srcFileAction.binaryAstFile)
         }
 
         return ModuleArtifact(moduleName, fileArtifacts, artifactsDir, forceRebuildJs, externalModuleName)
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/JsExecutableProducer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/JsExecutableProducer.kt
index a8e03c35f29..706681e0988 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/JsExecutableProducer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/JsExecutableProducer.kt
@@ -26,11 +26,11 @@ class JsExecutableProducer(
         }
     }
 
-    fun buildExecutable(multiModule: Boolean, outJsProgram: Boolean) = if (multiModule) {
-        buildMultiModuleExecutable(outJsProgram)
-    } else {
-        buildSingleModuleExecutable(outJsProgram)
-    }
+    fun buildExecutable(granularity: JsGenerationGranularity, outJsProgram: Boolean) =
+        when (granularity) {
+            JsGenerationGranularity.WHOLE_PROGRAM -> buildSingleModuleExecutable(outJsProgram)
+            JsGenerationGranularity.PER_MODULE, JsGenerationGranularity.PER_FILE -> buildMultiModuleExecutable(outJsProgram)
+        }
 
     private fun buildSingleModuleExecutable(outJsProgram: Boolean): BuildResult {
         val modules = caches.map { cacheArtifact -> cacheArtifact.loadJsIrModule() }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/JsMultiModuleCache.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/JsMultiModuleCache.kt
index 2d6ac9e8b03..a33b476b7a1 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/JsMultiModuleCache.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/JsMultiModuleCache.kt
@@ -30,7 +30,8 @@ class JsMultiModuleCache(private val moduleArtifacts: List<ModuleArtifact>) {
         val optionalCrossModuleImports = hashSetOf<String>()
 
         val crossModuleReferencesHash = ICHash.fromProtoStream(this)
-        val hasJsExports = readBool()
+        val reexportedInModuleWithName = ifTrue { readString() }
+
         repeat(readInt32()) {
             val tag = readString()
             val mask = readInt32()
@@ -44,6 +45,7 @@ class JsMultiModuleCache(private val moduleArtifacts: List<ModuleArtifact>) {
                 nameBindings[tag] = readString()
             }
         }
+
         CachedModuleInfo(
             artifact = this@fetchModuleInfo,
             jsIrHeader = JsIrModuleHeader(
@@ -52,7 +54,7 @@ class JsMultiModuleCache(private val moduleArtifacts: List<ModuleArtifact>) {
                 definitions = definitions,
                 nameBindings = nameBindings,
                 optionalCrossModuleImports = optionalCrossModuleImports,
-                hasJsExports = hasJsExports,
+                reexportedInModuleWithName = reexportedInModuleWithName,
                 associatedModule = null
             ),
             crossModuleReferencesHash = crossModuleReferencesHash
@@ -74,8 +76,13 @@ class JsMultiModuleCache(private val moduleArtifacts: List<ModuleArtifact>) {
                 names[tag] = ((maskAndName?.first ?: 0) or NameType.DEFINITIONS.typeMask) to maskAndName?.second
             }
             crossModuleReferencesHash.toProtoStream(this)
-            writeBoolNoTag(jsIrHeader.hasJsExports)
+
+            ifNotNull(jsIrHeader.reexportedInModuleWithName) {
+                writeStringNoTag(it)
+            }
+
             writeInt32NoTag(names.size)
+
             for ((tag, maskAndName) in names) {
                 writeStringNoTag(tag)
                 writeInt32NoTag(maskAndName.first)
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/ModuleArtifact.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/ModuleArtifact.kt
index a2281e8dc20..33d1dc232b1 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/ModuleArtifact.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/ModuleArtifact.kt
@@ -11,17 +11,17 @@ import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.safeModuleName
 import org.jetbrains.kotlin.ir.backend.js.utils.serialization.deserializeJsIrProgramFragment
 import java.io.File
 
-class SrcFileArtifact(val srcFilePath: String, private val fragment: JsIrProgramFragment?, private val astArtifact: File? = null) {
-    fun loadJsIrFragment(): JsIrProgramFragment? {
-        if (fragment != null) {
-            return fragment
+class SrcFileArtifact(val srcFilePath: String, private val fragments: List<JsIrProgramFragment>, private val astArtifact: File? = null) {
+    fun loadJsIrFragments(): List<JsIrProgramFragment> {
+        if (fragments.isNotEmpty()) {
+            return fragments
         }
         return astArtifact?.ifExists { readBytes() }?.let {
             deserializeJsIrProgramFragment(it)
-        }
+        } ?: emptyList()
     }
 
-    fun isModified() = fragment != null
+    fun isModified() = fragments.isNotEmpty()
 }
 
 class ModuleArtifact(
@@ -35,7 +35,7 @@ class ModuleArtifact(
     val moduleExternalName = externalModuleName ?: moduleSafeName
 
     fun loadJsIrModule(): JsIrModule {
-        val fragments = fileArtifacts.sortedBy { it.srcFilePath }.mapNotNull { it.loadJsIrFragment() }
+        val fragments = fileArtifacts.sortedBy { it.srcFilePath }.flatMap { it.loadJsIrFragments() }
         return JsIrModule(moduleSafeName, moduleExternalName, fragments)
     }
 }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6ConstructorLowering.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6ConstructorLowering.kt
index 7feb079c2dd..98e8a4e0be3 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6ConstructorLowering.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6ConstructorLowering.kt
@@ -226,7 +226,7 @@ class ES6ConstructorLowering(val context: JsIrBackendContext) : DeclarationTrans
                     constructor.isEffectivelyExternal() ->
                         JsIrBuilder.buildCall(context.intrinsics.jsCreateExternalThisSymbol)
                             .apply {
-                                putValueArgument(0, irClass.getCurrentConstructorReference(constructorReplacement))
+                                putValueArgument(0, getCurrentConstructorReference(constructorReplacement))
                                 putValueArgument(1, expression.symbol.owner.parentAsClass.jsConstructorReference(context))
                                 putValueArgument(2, irAnyArray(expression.valueArguments.memoryOptimizedMap { it ?: context.getVoid() }))
                                 putValueArgument(3, boxParameterGetter)
@@ -234,7 +234,7 @@ class ES6ConstructorLowering(val context: JsIrBackendContext) : DeclarationTrans
                     constructor.parentAsClass.symbol == context.irBuiltIns.anyClass ->
                         JsIrBuilder.buildCall(context.intrinsics.jsCreateThisSymbol)
                             .apply {
-                                putValueArgument(0, irClass.getCurrentConstructorReference(constructorReplacement))
+                                putValueArgument(0, getCurrentConstructorReference(constructorReplacement))
                                 putValueArgument(1, boxParameterGetter)
                             }
                     else ->
@@ -263,12 +263,8 @@ class ES6ConstructorLowering(val context: JsIrBackendContext) : DeclarationTrans
         }
     }
 
-    private fun IrClass.getCurrentConstructorReference(currentFactoryFunction: IrSimpleFunction): IrExpression {
-        return if (isFinalClass) {
-            jsConstructorReference(context)
-        } else {
-            JsIrBuilder.buildGetValue(currentFactoryFunction.dispatchReceiverParameter!!.symbol)
-        }
+    private fun getCurrentConstructorReference(currentFactoryFunction: IrSimpleFunction): IrExpression {
+        return JsIrBuilder.buildGetValue(currentFactoryFunction.dispatchReceiverParameter!!.symbol)
     }
 
     private fun IrDeclaration.excludeFromExport() {
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/JsPropertyAccessorInlineLowering.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/JsPropertyAccessorInlineLowering.kt
index 0aaedb2184f..65b69f3b399 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/JsPropertyAccessorInlineLowering.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/JsPropertyAccessorInlineLowering.kt
@@ -7,7 +7,6 @@ package org.jetbrains.kotlin.ir.backend.js.lower
 
 import org.jetbrains.kotlin.backend.common.lower.optimizations.PropertyAccessorInlineLowering
 import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
-import org.jetbrains.kotlin.ir.backend.js.codegen.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.declarations.IrDeclaration
 import org.jetbrains.kotlin.ir.declarations.IrProperty
 import org.jetbrains.kotlin.ir.util.fileOrNull
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/MoveOpenClassesToSeparateFiles.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/MoveOpenClassesToSeparateFiles.kt
deleted file mode 100644
index 033a4a09112..00000000000
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/MoveOpenClassesToSeparateFiles.kt
+++ /dev/null
@@ -1,62 +0,0 @@
-/*
- * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.ir.backend.js.lower
-
-import org.jetbrains.kotlin.descriptors.ClassKind
-import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
-import org.jetbrains.kotlin.descriptors.Modality
-import org.jetbrains.kotlin.ir.declarations.IrClass
-import org.jetbrains.kotlin.ir.declarations.IrDeclarationContainer
-import org.jetbrains.kotlin.ir.declarations.IrFile
-import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
-import org.jetbrains.kotlin.ir.declarations.impl.IrFileImpl
-import org.jetbrains.kotlin.ir.symbols.impl.IrFileSymbolImpl
-import org.jetbrains.kotlin.utils.memoryOptimizedPlus
-import org.jetbrains.kotlin.ir.util.transformDeclarationsFlat
-import org.jetbrains.kotlin.ir.util.transformFlat
-
-fun moveOpenClassesToSeparateFiles(moduleFragment: IrModuleFragment) {
-    fun createFile(file: IrFile, klass: IrClass): IrFile =
-        IrFileImpl(fileEntry = file.fileEntry, fqName = file.packageFqName, symbol = IrFileSymbolImpl(), module = file.module).also {
-            it.annotations = it.annotations memoryOptimizedPlus file.annotations
-            it.declarations += klass
-            klass.parent = it
-        }
-
-    moduleFragment.files.transformFlat { file ->
-        // We don't have to split declarations with a single class
-        if (file.declarations.size <= 1)
-            return@transformFlat null
-
-        val openClasses = mutableListOf<IrClass>()
-        fun removeAndCollectOpenClasses(container: IrDeclarationContainer) {
-            container.transformDeclarationsFlat { declaration ->
-                if (declaration is IrDeclarationContainer) {
-                    removeAndCollectOpenClasses(declaration)
-                }
-                if (
-                    declaration is IrClass &&
-                    (declaration.modality == Modality.OPEN || declaration.modality == Modality.ABSTRACT) &&
-                    declaration.kind == ClassKind.CLASS &&
-                    declaration.visibility != DescriptorVisibilities.PRIVATE &&
-                    declaration.visibility != DescriptorVisibilities.LOCAL
-                ) {
-                    openClasses += declaration
-                    emptyList()
-                } else {
-                    null
-                }
-            }
-        }
-        removeAndCollectOpenClasses(file)
-
-        return@transformFlat if (openClasses.isEmpty())
-            null
-        else
-            openClasses.mapTo(mutableListOf(file)) { createFile(file, it) }
-    }
-}
-
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt
index 725116d790e..74cf3cd313c 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt
@@ -8,9 +8,7 @@ package org.jetbrains.kotlin.ir.backend.js.transformers.irToJs
 import org.jetbrains.kotlin.backend.common.compilationException
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.ir.backend.js.JsStatementOrigins
-import org.jetbrains.kotlin.ir.backend.js.utils.JsGenerationContext
-import org.jetbrains.kotlin.ir.backend.js.utils.Namer
-import org.jetbrains.kotlin.ir.backend.js.utils.getJsNameOrKotlinName
+import org.jetbrains.kotlin.ir.backend.js.utils.*
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.types.isString
@@ -169,7 +167,7 @@ class IrElementToJsExpressionTransformer : BaseIrElementToJsNodeTransformer<JsEx
     }
 
     override fun visitDelegatingConstructorCall(expression: IrDelegatingConstructorCall, context: JsGenerationContext): JsExpression {
-        val classNameRef = context.getNameForConstructor(expression.symbol.owner).makeRef()
+        val classNameRef = expression.symbol.owner.getConstructorRef(context.staticContext)
         val callFuncRef = JsNameRef(Namer.CALL_FUNCTION, classNameRef)
         val fromPrimary = context.currentFunction is IrConstructor
         val thisRef =
@@ -202,7 +200,7 @@ class IrElementToJsExpressionTransformer : BaseIrElementToJsNodeTransformer<JsEx
 
         return when {
             klass.isEffectivelyExternal() -> {
-                val refForExternalClass = context.getRefForExternalClass(klass)
+                val refForExternalClass = klass.getClassRef(context.staticContext)
                 val varargParameterIndex = expression.symbol.owner.varargParameterIndex()
                 if (varargParameterIndex == -1) {
                     JsNew(refForExternalClass, arguments)
@@ -225,8 +223,7 @@ class IrElementToJsExpressionTransformer : BaseIrElementToJsNodeTransformer<JsEx
                 }
             }
             else -> {
-                val ref = context.getNameForClass(klass).makeRef()
-                JsNew(ref, arguments)
+                JsNew(klass.getClassRef(context.staticContext), arguments)
             }
         }.withSource(expression, context)
     }
@@ -320,14 +317,14 @@ class IrElementToJsExpressionTransformer : BaseIrElementToJsNodeTransformer<JsEx
 
     override fun visitRawFunctionReference(expression: IrRawFunctionReference, data: JsGenerationContext): JsExpression {
         val name = when (val function = expression.symbol.owner) {
-            is IrConstructor -> data.getNameForConstructor(function)
-            is IrSimpleFunction -> data.getNameForStaticFunction(function)
+            is IrConstructor -> function.getConstructorRef(data.staticContext)
+            is IrSimpleFunction -> data.getNameForStaticFunction(function).makeRef()
             else -> compilationException(
                 "Unexpected function kind",
                 expression
             )
         }
-        return JsNameRef(name).withSource(expression, data)
+        return name.withSource(expression, data)
     }
 
     private fun prefixOperation(operator: JsUnaryOperator, expression: IrDynamicOperatorExpression, data: JsGenerationContext) =
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformer.kt
index 0eb2b518431..08496bfb211 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformer.kt
@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.backend.common.serialization.checkIsFunctionInterfac
 import org.jetbrains.kotlin.config.CommonConfigurationKeys
 import org.jetbrains.kotlin.ir.backend.js.*
 import org.jetbrains.kotlin.ir.backend.js.export.*
+import org.jetbrains.kotlin.ir.backend.js.lower.JsCodeOutliningLowering
 import org.jetbrains.kotlin.ir.backend.js.lower.StaticMembersLowering
 import org.jetbrains.kotlin.ir.backend.js.lower.isBuiltInClass
 import org.jetbrains.kotlin.ir.backend.js.utils.*
@@ -45,34 +46,51 @@ val String.safeModuleName: String
 val IrModuleFragment.safeName: String
     get() = name.asString().safeModuleName
 
+enum class JsGenerationGranularity {
+    WHOLE_PROGRAM,
+    PER_MODULE,
+    PER_FILE
+}
+
 enum class TranslationMode(
     val production: Boolean,
-    val perModule: Boolean,
+    val granularity: JsGenerationGranularity,
     val minimizedMemberNames: Boolean,
 ) {
-    FULL_DEV(production = false, perModule = false, minimizedMemberNames = false),
-    FULL_PROD(production = true, perModule = false, minimizedMemberNames = false),
-    FULL_PROD_MINIMIZED_NAMES(production = true, perModule = false, minimizedMemberNames = true),
-    PER_MODULE_DEV(production = false, perModule = true, minimizedMemberNames = false),
-    PER_MODULE_PROD(production = true, perModule = true, minimizedMemberNames = false),
-    PER_MODULE_PROD_MINIMIZED_NAMES(production = true, perModule = true, minimizedMemberNames = true);
+    FULL_DEV(production = false, granularity = JsGenerationGranularity.WHOLE_PROGRAM, minimizedMemberNames = false),
+    FULL_PROD(production = true, granularity = JsGenerationGranularity.WHOLE_PROGRAM, minimizedMemberNames = false),
+    FULL_PROD_MINIMIZED_NAMES(production = true, granularity = JsGenerationGranularity.WHOLE_PROGRAM, minimizedMemberNames = true),
+    PER_MODULE_DEV(production = false, granularity = JsGenerationGranularity.PER_MODULE, minimizedMemberNames = false),
+    PER_MODULE_PROD(production = true, granularity = JsGenerationGranularity.PER_MODULE, minimizedMemberNames = false),
+    PER_MODULE_PROD_MINIMIZED_NAMES(production = true, granularity = JsGenerationGranularity.PER_MODULE, minimizedMemberNames = true),
+    PER_FILE_DEV(production = false, granularity = JsGenerationGranularity.PER_FILE, minimizedMemberNames = false),
+    PER_FILE_PROD(production = true, granularity = JsGenerationGranularity.PER_FILE, minimizedMemberNames = false),
+    PER_FILE_PROD_MINIMIZED_NAMES(production = true, granularity = JsGenerationGranularity.PER_FILE, minimizedMemberNames = true);
 
     companion object {
         fun fromFlags(
             production: Boolean,
-            perModule: Boolean,
+            granularity: JsGenerationGranularity,
             minimizedMemberNames: Boolean
         ): TranslationMode {
-            return if (perModule) {
-                if (production) {
-                    if (minimizedMemberNames) PER_MODULE_PROD_MINIMIZED_NAMES
-                    else PER_MODULE_PROD
-                } else PER_MODULE_DEV
-            } else {
-                if (production) {
-                    if (minimizedMemberNames) FULL_PROD_MINIMIZED_NAMES
-                    else FULL_PROD
-                } else FULL_DEV
+            return when (granularity) {
+                JsGenerationGranularity.PER_MODULE ->
+                    if (production) {
+                        if (minimizedMemberNames) PER_MODULE_PROD_MINIMIZED_NAMES
+                        else PER_MODULE_PROD
+                    } else PER_MODULE_DEV
+
+                JsGenerationGranularity.PER_FILE ->
+                    if (production) {
+                        if (minimizedMemberNames) PER_FILE_PROD_MINIMIZED_NAMES
+                        else PER_FILE_PROD
+                    } else PER_FILE_DEV
+
+                JsGenerationGranularity.WHOLE_PROGRAM ->
+                    if (production) {
+                        if (minimizedMemberNames) FULL_PROD_MINIMIZED_NAMES
+                        else FULL_PROD
+                    } else FULL_DEV
             }
         }
     }
@@ -80,14 +98,14 @@ enum class TranslationMode(
 
 class JsCodeGenerator(
     private val program: JsIrProgram,
-    private val multiModule: Boolean,
+    private val granularity: JsGenerationGranularity,
     private val mainModuleName: String,
     private val moduleKind: ModuleKind,
     private val sourceMapsInfo: SourceMapsInfo?
 ) {
     fun generateJsCode(relativeRequirePath: Boolean, outJsProgram: Boolean): CompilationOutputsBuilt {
         return generateWrappedModuleBody(
-            multiModule,
+            granularity,
             mainModuleName,
             moduleKind,
             program,
@@ -101,7 +119,7 @@ class JsCodeGenerator(
 class IrModuleToJsTransformer(
     private val backendContext: JsIrBackendContext,
     private val mainArguments: List<String>?,
-    private val moduleToName: Map<IrModuleFragment, String> = emptyMap(),
+    moduleToName: Map<IrModuleFragment, String> = emptyMap(),
     private val removeUnusedAssociatedObjects: Boolean = true,
 ) {
     private val shouldGeneratePolyfills = backendContext.configuration.getBoolean(JSConfigurationKeys.GENERATE_POLYFILLS)
@@ -113,7 +131,14 @@ class IrModuleToJsTransformer(
     private val isEsModules = moduleKind == ModuleKind.ES
     private val sourceMapInfo = SourceMapsInfo.from(backendContext.configuration)
 
-    private class IrFileExports(val file: IrFile, val exports: List<ExportedDeclaration>, val tsDeclarations: TypeScriptFragment?)
+    private val moduleFragmentToNameMapper = ModuleFragmentToExternalName(moduleToName)
+
+    private class IrFileExports(
+        val file: IrFile,
+        val exports: List<ExportedDeclaration>,
+        val tsDeclarations: TypeScriptFragment?,
+        val generatedFrom: IrFile? = null
+    )
 
     private class IrAndExportedDeclarations(val fragment: IrModuleFragment, val files: List<IrFileExports>)
 
@@ -172,15 +197,22 @@ class IrModuleToJsTransformer(
         return makeJsCodeGeneratorFromIr(exportData, mode)
     }
 
-    fun makeIrFragmentsGenerators(files: Collection<IrFile>, allModules: Collection<IrModuleFragment>): List<() -> JsIrProgramFragment> {
+    fun makeIrFragmentsGenerators(
+        dirtyFiles: Collection<IrFile>,
+        allModules: Collection<IrModuleFragment>
+    ): List<() -> List<JsIrProgramFragment>> {
+        val files = dirtyFiles + backendContext.mapping.chunkToOriginalFile.keys
         val exportModelGenerator = ExportModelGenerator(backendContext, generateNamespacesForPackages = !isEsModules)
         val exportData = exportModelGenerator.generateExportWithExternals(files)
+        val mode = TranslationMode.fromFlags(production = false, backendContext.granularity, minimizedMemberNames = false)
 
         doStaticMembersLowering(allModules)
 
-        return exportData.map {
-            { generateProgramFragment(it, minimizedMemberNames = false) }
-        }
+        return exportData
+            .groupBy { it.generatedFrom ?: it.file }
+            .map {
+                { it.value.flatMap { generateProgramFragment(it, mode) } }
+            }
     }
 
     private fun ExportModelGenerator.generateExportWithExternals(irFiles: Collection<IrFile>): List<IrFileExports> {
@@ -191,47 +223,123 @@ class IrModuleToJsTransformer(
             val tsDeclarations = runIf(shouldGenerateTypeScriptDefinitions) {
                 allExports.ifNotEmpty { toTypeScriptFragment(moduleKind) }
             }
-            IrFileExports(irFile, allExports, tsDeclarations)
+            IrFileExports(irFile, allExports, tsDeclarations, context.mapping.chunkToOriginalFile[irFile])
         }
     }
 
-    private fun IrModuleFragment.externalModuleName(): String {
-        return moduleToName[this] ?: sanitizeName(safeName)
-    }
-
     private fun makeJsCodeGeneratorFromIr(exportData: List<IrAndExportedDeclarations>, mode: TranslationMode): JsCodeGenerator {
         if (mode.minimizedMemberNames) {
             backendContext.fieldDataCache.clear()
             backendContext.minimizedNameGenerator.clear()
         }
 
-        val program = JsIrProgram(
+        val program = when (mode.granularity) {
+            JsGenerationGranularity.WHOLE_PROGRAM, JsGenerationGranularity.PER_MODULE -> generateJsIrProgramPerModule(exportData, mode)
+            JsGenerationGranularity.PER_FILE -> generateJsIrProgramPerFile(exportData, mode)
+        }
+
+        return JsCodeGenerator(program, mode.granularity, mainModuleName, moduleKind, sourceMapInfo)
+    }
+
+    private fun generateJsIrProgramPerModule(exportData: List<IrAndExportedDeclarations>, mode: TranslationMode): JsIrProgram {
+        val mainModule = exportData.last()
+
+        return JsIrProgram(
             exportData.map { data ->
                 JsIrModule(
                     data.fragment.safeName,
-                    data.fragment.externalModuleName(),
-                    data.files.map { generateProgramFragment(it, mode.minimizedMemberNames) }
+                    moduleFragmentToNameMapper.getExternalNameFor(data.fragment),
+                    data.files.flatMap { generateProgramFragment(it, mode) },
+                    mainModule.fragment.safeName.takeIf { !isEsModules && data != mainModule }
                 )
             }
         )
+    }
 
-        return JsCodeGenerator(program, mode.perModule, mainModuleName, moduleKind, sourceMapInfo)
+    private fun generateJsIrProgramPerFile(exportData: List<IrAndExportedDeclarations>, mode: TranslationMode): JsIrProgram {
+        val modulesPerFile = buildList {
+            for (module in exportData) {
+                var hasFileWithJsExportedDeclaration = false
+
+                for (fileExports in module.files) {
+                    if (fileExports.file.couldBeSkipped()) continue
+                    val (programFragment, exportProgramFragment) = generateProgramFragment(fileExports, mode)
+
+                    add(fileExports.toJsIrModule(mode, programFragment))
+
+                    if (fileExports.exports.isNotEmpty()) {
+                        add(fileExports.toJsIrModuleForExport(module, mode, exportProgramFragment))
+                        hasFileWithJsExportedDeclaration = true
+                    }
+                }
+
+                if (hasFileWithJsExportedDeclaration) {
+                    add(module.toJsIrProxyModule())
+                }
+            }
+        }
+
+        return JsIrProgram(modulesPerFile)
+    }
+
+    private fun IrFileExports.toJsIrModule(mode: TranslationMode, programFragment: JsIrProgramFragment): JsIrModule {
+        return JsIrModule(
+            moduleFragmentToNameMapper.getSafeNameFor(file),
+            moduleFragmentToNameMapper.getExternalNameFor(file, mode.granularity),
+            listOf(programFragment),
+        )
+    }
+
+    private fun IrFileExports.toJsIrModuleForExport(
+        module: IrAndExportedDeclarations,
+        mode: TranslationMode,
+        programFragment: JsIrProgramFragment
+    ): JsIrModule {
+        return JsIrModule(
+            moduleFragmentToNameMapper.getSafeNameExporterFor(file),
+            moduleFragmentToNameMapper.getExternalNameForExporterFile(file, mode.granularity),
+            listOf(programFragment),
+            module.fragment.safeName
+        )
+    }
+
+    private fun IrAndExportedDeclarations.toJsIrProxyModule(): JsIrModule {
+        return JsIrModule(
+            fragment.safeName,
+            moduleFragmentToNameMapper.getExternalNameFor(fragment),
+            listOf(JsIrProgramFragment("<proxy-file>"))
+        )
     }
 
     private val generateFilePaths = backendContext.configuration.getBoolean(JSConfigurationKeys.GENERATE_COMMENTS_WITH_FILE_PATH)
     private val pathPrefixMap = backendContext.configuration.getMap(JSConfigurationKeys.FILE_PATHS_PREFIX_MAP)
     private val optimizeGeneratedJs = backendContext.configuration.get(JSConfigurationKeys.OPTIMIZE_GENERATED_JS, true)
 
-    private fun generateProgramFragment(fileExports: IrFileExports, minimizedMemberNames: Boolean): JsIrProgramFragment {
-        val nameGenerator = JsNameLinkingNamer(backendContext, minimizedMemberNames, isEsModules)
+    private fun IrFileExports.generateProgramFragmentForExport(
+        mode: TranslationMode,
+        nameScope: NameTable<IrDeclaration>
+    ): JsIrProgramFragment {
+        val globalNames = NameTable<String>(nameScope)
+        val nameGenerator = JsNameLinkingNamer(backendContext, mode.minimizedMemberNames, isEsModules)
+        val internalModuleName = ReservedJsNames.makeInternalModuleName().takeIf { !isEsModules }
+        val staticContext = JsStaticContext(backendContext, nameGenerator, nameScope, mode)
 
+        return JsIrProgramFragment(file.packageFqName.asString()).apply {
+            dts = tsDeclarations
+            exports.statements += ExportModelToJsStatements(staticContext, backendContext.es6mode, { globalNames.declareFreshName(it, it) })
+                .generateModuleExport(
+                    ExportedModule(mainModuleName, moduleKind, this@generateProgramFragmentForExport.exports),
+                    internalModuleName,
+                    isEsModules
+                )
+            computeAndSaveNameBindings(emptySet(), nameGenerator)
+        }
+    }
+
+    private fun generateProgramFragment(fileExports: IrFileExports, mode: TranslationMode): List<JsIrProgramFragment> {
         val globalNameScope = NameTable<IrDeclaration>()
-
-        val staticContext = JsStaticContext(
-            backendContext = backendContext,
-            irNamer = nameGenerator,
-            globalNameScope = globalNameScope
-        )
+        val nameGenerator = JsNameLinkingNamer(backendContext, mode.minimizedMemberNames, isEsModules)
+        val staticContext = JsStaticContext(backendContext, nameGenerator, globalNameScope, mode)
 
         val result = JsIrProgramFragment(fileExports.file.packageFqName.asString()).apply {
             if (shouldGeneratePolyfills) {
@@ -239,21 +347,9 @@ class IrModuleToJsTransformer(
             }
         }
 
-        val internalModuleName = ReservedJsNames.makeInternalModuleName().takeIf { !isEsModules }
-        val globalNames = NameTable<String>(globalNameScope)
-
         val statements = result.declarations.statements
         val fileStatements = fileExports.file.accept(IrFileToJsTransformer(useBareParameterNames = true), staticContext).statements
-
-        val exportStatements =
-            ExportModelToJsStatements(staticContext, backendContext.es6mode, { globalNames.declareFreshName(it, it) }).generateModuleExport(
-                ExportedModule(mainModuleName, moduleKind, fileExports.exports),
-                internalModuleName,
-                isEsModules
-            )
-
-        result.exports.statements += exportStatements
-        result.dts = fileExports.tsDeclarations
+        val exportFragment = fileExports.generateProgramFragmentForExport(mode, globalNameScope)
 
         if (fileStatements.isNotEmpty()) {
             var startComment = ""
@@ -310,50 +406,69 @@ class IrModuleToJsTransformer(
 
         val definitionSet = fileExports.file.declarations.toSet()
 
-        fun computeTag(declaration: IrDeclaration): String? {
-            val tag = (backendContext.irFactory as IdSignatureRetriever).declarationSignature(declaration)?.toString()
-
-            if (tag == null && declaration !in definitionSet) {
-                error("signature for ${declaration.render()} not found")
-            }
-
-            return tag
-        }
-
-        nameGenerator.nameMap.entries.forEach { (declaration, name) ->
-            computeTag(declaration)?.let { tag ->
-                result.nameBindings[tag] = name
-                if (isBuiltInClass(declaration) || checkIsFunctionInterface(declaration.symbol.signature)) {
-                    result.optionalCrossModuleImports += tag
-                }
-            }
-        }
-
-        nameGenerator.imports.entries.forEach { (declaration, importStatement) ->
-            val tag = computeTag(declaration) ?: error("No tag for imported declaration ${declaration.render()}")
-            result.imports[tag] = importStatement
-            result.optionalCrossModuleImports += tag
-        }
-
-        fileExports.file.declarations.forEach {
-            computeTag(it)?.let { tag ->
-                result.definitions += tag
-            }
-
-            if (it is IrClass && it.isInterface) {
-                it.declarations.forEach {
-                    computeTag(it)?.let { tag ->
-                        result.definitions += tag
-                    }
-                }
-            }
-        }
+        result.computeAndSaveNameBindings(definitionSet, nameGenerator)
+        result.computeAndSaveImports(definitionSet, nameGenerator)
+        result.computeAndSaveDefinitions(definitionSet, fileExports)
 
         if (optimizeGeneratedJs) {
             optimizeFragmentByJsAst(result)
         }
 
-        return result
+        return listOf(result, exportFragment)
+    }
+
+    private fun Set<IrDeclaration>.computeTag(declaration: IrDeclaration): String? {
+        val tag = (backendContext.irFactory as IdSignatureRetriever).declarationSignature(declaration)?.toString()
+
+        if (tag == null && !contains(declaration)) {
+            error("signature for ${declaration.render()} not found")
+        }
+
+        return tag
+    }
+
+    private fun JsIrProgramFragment.computeAndSaveNameBindings(
+        definitions: Set<IrDeclaration>,
+        nameGenerator: JsNameLinkingNamer
+    ) {
+        nameGenerator.nameMap.entries.forEach { (declaration, name) ->
+            definitions.computeTag(declaration)?.let { tag ->
+                nameBindings[tag] = name
+                if (isBuiltInClass(declaration) || checkIsFunctionInterface(declaration.symbol.signature)) {
+                    optionalCrossModuleImports += tag
+                }
+            }
+        }
+    }
+
+    private fun JsIrProgramFragment.computeAndSaveImports(
+        definitions: Set<IrDeclaration>,
+        nameGenerator: JsNameLinkingNamer
+    ) {
+        nameGenerator.imports.entries.forEach { (declaration, importExpression) ->
+            val tag = definitions.computeTag(declaration) ?: error("No tag for imported declaration ${declaration.render()}")
+            imports[tag] = importExpression
+            optionalCrossModuleImports += tag
+        }
+    }
+
+    private fun JsIrProgramFragment.computeAndSaveDefinitions(
+        definitions: Set<IrDeclaration>,
+        fileExports: IrFileExports,
+    ) {
+        fileExports.file.declarations.forEach {
+            definitions.computeTag(it)?.let { tag ->
+                this.definitions += tag
+            }
+
+            if (it is IrClass && it.isInterface) {
+                it.declarations.forEach {
+                    definitions.computeTag(it)?.let { tag ->
+                        this.definitions += tag
+                    }
+                }
+            }
+        }
     }
 
     private fun generateMainArguments(
@@ -374,10 +489,12 @@ class IrModuleToJsTransformer(
 
         return listOfNotNull(mainArgumentsArray, continuation)
     }
+
+    private fun IrFile.couldBeSkipped(): Boolean = declarations.all { it.origin == JsCodeOutliningLowering.OUTLINED_JS_CODE_ORIGIN }
 }
 
 private fun generateWrappedModuleBody(
-    multiModule: Boolean,
+    granularity: JsGenerationGranularity,
     mainModuleName: String,
     moduleKind: ModuleKind,
     program: JsIrProgram,
@@ -385,44 +502,8 @@ private fun generateWrappedModuleBody(
     relativeRequirePath: Boolean,
     outJsProgram: Boolean
 ): CompilationOutputsBuilt {
-    if (multiModule) {
-        // mutable container allows explicitly remove elements from itself,
-        // so we are able to help GC to free heavy JsIrModule objects
-        // TODO: It makes sense to invent something better, because this logic can be easily broken
-        val moduleToRef = program.asCrossModuleDependencies(moduleKind, relativeRequirePath).toMutableList()
-        val mainModule = moduleToRef.removeLast().let { (main, mainRef) ->
-            generateSingleWrappedModuleBody(
-                mainModuleName,
-                moduleKind,
-                main.fragments,
-                sourceMapsInfo,
-                generateCallToMain = true,
-                mainRef,
-                outJsProgram
-            )
-        }
-
-        mainModule.dependencies = buildList(moduleToRef.size) {
-            while (moduleToRef.isNotEmpty()) {
-                moduleToRef.removeFirst().let { (module, moduleRef) ->
-                    val moduleName = module.externalModuleName
-                    val moduleCompilationOutput = generateSingleWrappedModuleBody(
-                        moduleName,
-                        moduleKind,
-                        module.fragments,
-                        sourceMapsInfo,
-                        generateCallToMain = false,
-                        moduleRef,
-                        outJsProgram
-                    )
-                    add(moduleName to moduleCompilationOutput)
-                }
-            }
-        }
-
-        return mainModule
-    } else {
-        return generateSingleWrappedModuleBody(
+    return when (granularity) {
+        JsGenerationGranularity.WHOLE_PROGRAM -> generateSingleWrappedModuleBody(
             mainModuleName,
             moduleKind,
             program.asFragments(),
@@ -430,9 +511,64 @@ private fun generateWrappedModuleBody(
             generateCallToMain = true,
             outJsProgram = outJsProgram
         )
+        JsGenerationGranularity.PER_FILE,
+        JsGenerationGranularity.PER_MODULE -> generateMultiWrappedModuleBody(
+            mainModuleName,
+            moduleKind,
+            program,
+            sourceMapsInfo,
+            relativeRequirePath,
+            outJsProgram
+        )
     }
 }
 
+private fun generateMultiWrappedModuleBody(
+    mainModuleName: String,
+    moduleKind: ModuleKind,
+    program: JsIrProgram,
+    sourceMapsInfo: SourceMapsInfo?,
+    relativeRequirePath: Boolean,
+    outJsProgram: Boolean
+): CompilationOutputsBuilt {
+    // mutable container allows explicitly remove elements from itself,
+    // so we are able to help GC to free heavy JsIrModule objects
+    // TODO: It makes sense to invent something better, because this logic can be easily broken
+    val moduleToRef = program.asCrossModuleDependencies(moduleKind, relativeRequirePath).toMutableList()
+
+    val mainModule = moduleToRef.removeLast().let { (main, mainRef) ->
+        generateSingleWrappedModuleBody(
+            mainModuleName,
+            moduleKind,
+            main.fragments,
+            sourceMapsInfo,
+            generateCallToMain = true,
+            mainRef,
+            outJsProgram
+        )
+    }
+
+    mainModule.dependencies = buildList(moduleToRef.size) {
+        while (moduleToRef.isNotEmpty()) {
+            moduleToRef.removeFirst().let { (module, moduleRef) ->
+                val moduleName = module.externalModuleName
+                val moduleCompilationOutput = generateSingleWrappedModuleBody(
+                    moduleName,
+                    moduleKind,
+                    module.fragments,
+                    sourceMapsInfo,
+                    generateCallToMain = false,
+                    moduleRef,
+                    outJsProgram
+                )
+                add(moduleName to moduleCompilationOutput)
+            }
+        }
+    }
+
+    return mainModule
+}
+
 fun generateSingleWrappedModuleBody(
     moduleName: String,
     moduleKind: ModuleKind,
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsClassGenerator.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsClassGenerator.kt
index ba1675df3d7..cc4acec8ec5 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsClassGenerator.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsClassGenerator.kt
@@ -20,55 +20,96 @@ import org.jetbrains.kotlin.ir.symbols.IrClassifierSymbol
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.js.backend.ast.*
+import org.jetbrains.kotlin.js.backend.ast.JsVars.JsVar
 import org.jetbrains.kotlin.js.common.isValidES5Identifier
 import org.jetbrains.kotlin.utils.addIfNotNull
+import org.jetbrains.kotlin.utils.addToStdlib.butIf
 import org.jetbrains.kotlin.utils.memoryOptimizedMap
 import org.jetbrains.kotlin.utils.toSmartList
 
 class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationContext) {
+    private val perFile = context.staticContext.isPerFile
+    private val es6mode = context.staticContext.backendContext.es6mode
+
     private val className = context.getNameForClass(irClass)
-    private val classNameRef = className.makeRef()
     private val baseClass: IrType? = irClass.superTypes.firstOrNull { !it.classifierOrFail.isInterface }
 
+    private val classNameUsedInsideDeclarationStatements = when {
+        perFile -> JsName("$", true)
+        else -> className
+    }
+
+    private val classNameRef = classNameUsedInsideDeclarationStatements.makeRef()
+
     private val classPrototypeRef by lazy(LazyThreadSafetyMode.NONE) { prototypeOf(classNameRef, context.staticContext) }
     private val baseClassRef by lazy(LazyThreadSafetyMode.NONE) { // Lazy in case was not collected by namer during JsClassGenerator construction
-        if (baseClass != null && !baseClass.isAny()) baseClass.getClassRef(context) else null
+        if (baseClass != null && !baseClass.isAny()) baseClass.getClassRef(context.staticContext) else null
     }
-    private val classBlock = JsCompositeBlock()
     private val classModel = JsIrClassModel(irClass)
+    private val classBlock = JsCompositeBlock()
 
-    private val es6mode = context.staticContext.backendContext.es6mode
+    private val interfaceDefaultsBlock = when {
+        perFile -> JsCompositeBlock()
+        else -> classModel.preDeclarationBlock
+    }
+
+    private val jsUndefined by lazy(LazyThreadSafetyMode.NONE) { jsUndefined(context.staticContext) }
 
     fun generate(): JsStatement {
+        return generateClassBlock().butIf(perFile) { it.wrapInFunction() }
+    }
+
+    private fun JsCompositeBlock.wrapInFunction(): JsStatement {
+        val classHolder = JsVar(JsName("${className.ident}Class", true))
+        val functionWrapper = JsFunction(emptyScope, JsBlock(), "lazy wrapper for classes in per-file").apply {
+            name = className
+            with(body.statements) {
+                add(
+                    JsIf(
+                        JsAstUtils.equality(classHolder.name.makeRef(), jsUndefined),
+                        JsBlock(
+                            classModel.preDeclarationBlock.statements + statements + classModel.postDeclarationBlock.statements +
+                                    JsAstUtils.assignment(classHolder.name.makeRef(), classNameRef).makeStmt()
+                        )
+                    )
+                )
+                add(JsReturn(classHolder.name.makeRef()))
+            }
+        }
+
+        return JsCompositeBlock(interfaceDefaultsBlock.statements + listOf(JsVars(classHolder), functionWrapper.makeStmt())).also {
+            classModel.preDeclarationBlock.statements.clear()
+            classModel.postDeclarationBlock.statements.clear()
+        }
+    }
+
+    private fun generateClassBlock(): JsCompositeBlock {
         assert(!irClass.isExpect)
 
         if (!es6mode) maybeGeneratePrimaryConstructor()
 
-        val transformer = IrDeclarationToJsTransformer()
-
         // Properties might be lowered out of classes
         // We'll use IrSimpleFunction::correspondingProperty to collect them into set
         val properties = mutableSetOf<IrProperty>()
 
-        val jsClass = JsClass(name = className, baseClass = baseClassRef)
+        val jsClass = JsClass(name = classNameUsedInsideDeclarationStatements, baseClass = baseClassRef)
 
         if (baseClass != null && !baseClass.isAny()) {
             jsClass.baseClass = baseClassRef
         }
 
-        if (es6mode) classModel.preDeclarationBlock.statements += jsClass.makeStmt()
+        if (es6mode) {
+            classModel.preDeclarationBlock.statements += jsClass.makeStmt()
+        }
 
         for (declaration in irClass.declarations) {
             when (declaration) {
                 is IrConstructor -> {
+                    val constructor = declaration.accept(IrFunctionToJsTransformer(), context)
                     if (es6mode) {
-                        declaration.accept(IrFunctionToJsTransformer(), context).let { fn ->
-                            if (fn.body.statements.any { it !is JsEmpty && !it.isSimpleSuperCall(fn) }) {
-                                jsClass.constructor = fn
-                            }
-                        }
+                        jsClass.constructor = constructor.apply { name = null }
                     } else {
-                        classBlock.statements += declaration.accept(transformer, context)
+                        classBlock.statements += constructor.apply { name = classNameUsedInsideDeclarationStatements }.makeStmt()
                     }
                 }
                 is IrSimpleFunction -> {
@@ -275,7 +316,7 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
             assert(!declaration.isStaticMethodOfClass)
 
             if (irClass.isInterface) {
-                classModel.preDeclarationBlock.statements += translatedFunction.makeStmt()
+                interfaceDefaultsBlock.statements += translatedFunction.makeStmt()
                 return Pair(memberName, null)
             }
 
@@ -323,7 +364,7 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
     private fun maybeGeneratePrimaryConstructor() {
         if (!irClass.declarations.any { it is IrConstructor }) {
             val func = JsFunction(emptyScope, JsBlock(), "Ctor for ${irClass.name}")
-            func.name = className
+            func.name = classNameUsedInsideDeclarationStatements
             classBlock.statements += func.makeStmt()
         }
     }
@@ -352,12 +393,12 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
     }
 
 
-    private fun IrType.asConstructorRef(): JsNameRef? {
+    private fun IrType.asConstructorRef(): JsExpression? {
         val ownerSymbol = classOrNull?.takeIf {
             !isAny() && !isFunctionType() && !it.owner.isEffectivelyExternal()
         } ?: return null
 
-        return JsNameRef(context.getNameForClass(ownerSymbol.owner))
+        return ownerSymbol.owner.getClassRef(context.staticContext)
     }
 
     private fun IrType.isFunctionType() = isFunctionOrKFunction() || isSuspendFunctionOrKFunction()
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsIntrinsicTransformers.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsIntrinsicTransformers.kt
index 324422baa92..b5527116965 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsIntrinsicTransformers.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsIntrinsicTransformers.kt
@@ -7,10 +7,7 @@ package org.jetbrains.kotlin.ir.backend.js.transformers.irToJs
 
 import org.jetbrains.kotlin.backend.common.compilationException
 import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
-import org.jetbrains.kotlin.ir.backend.js.utils.JsGenerationContext
-import org.jetbrains.kotlin.ir.backend.js.utils.Namer
-import org.jetbrains.kotlin.ir.backend.js.utils.getClassRef
-import org.jetbrains.kotlin.ir.backend.js.utils.invokeFunForLambda
+import org.jetbrains.kotlin.ir.backend.js.utils.*
 import org.jetbrains.kotlin.ir.declarations.IrClass
 import org.jetbrains.kotlin.ir.declarations.IrConstructor
 import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
@@ -91,13 +88,13 @@ class JsIntrinsicTransformers(backendContext: JsIrBackendContext) {
 
             add(intrinsics.jsObjectCreateSymbol) { call, context ->
                 val classToCreate = call.getTypeArgument(0)!!.classifierOrFail.owner as IrClass
-                val className = context.getNameForClass(classToCreate)
-                objectCreate(prototypeOf(className.makeRef(), context.staticContext), context.staticContext)
+                val className = classToCreate.getClassRef(context.staticContext)
+                objectCreate(prototypeOf(className, context.staticContext), context.staticContext)
             }
 
             add(intrinsics.jsClass) { call, context ->
                 val typeArgument = call.getTypeArgument(0)
-                typeArgument?.getClassRef(context)
+                typeArgument?.getClassRef(context.staticContext)
                     ?: compilationException(
                         "Type argument of jsClass must be statically known class",
                         typeArgument
@@ -180,7 +177,8 @@ class JsIntrinsicTransformers(backendContext: JsIrBackendContext) {
                 val arg = translateCallArguments(call, context).single()
                 val inlineClass = icUtils.getInlinedClass(call.getTypeArgument(0)!!)!!
                 val constructor = inlineClass.declarations.filterIsInstance<IrConstructor>().single { it.isPrimary }
-                JsNew(context.getNameForConstructor(constructor).makeRef(), listOf(arg))
+
+                JsNew(constructor.getConstructorRef(context.staticContext), listOf(arg))
                     .apply { isInlineClassBoxing = true }
             }
 
@@ -209,7 +207,7 @@ class JsIntrinsicTransformers(backendContext: JsIrBackendContext) {
                     is IrFunctionReference -> {
                         val superClass = call.superQualifierSymbol!!
                         val functionName = context.getNameForMemberFunction(target.symbol.owner as IrSimpleFunction)
-                        val superName = context.getNameForClass(superClass.owner).makeRef()
+                        val superName = superClass.owner.getClassRef(context.staticContext)
                         JsNameRef(functionName, prototypeOf(superName, context.staticContext))
                     }
                     is IrFunctionExpression -> target.accept(IrElementToJsExpressionTransformer(), context)
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsIrProgramFragment.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsIrProgramFragment.kt
index 87c5b0ce153..3e5ef6523a0 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsIrProgramFragment.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsIrProgramFragment.kt
@@ -31,15 +31,16 @@ class JsIrProgramFragment(val packageFqn: String) {
 class JsIrModule(
     val moduleName: String,
     val externalModuleName: String,
-    val fragments: List<JsIrProgramFragment>
+    val fragments: List<JsIrProgramFragment>,
+    val reexportedInModuleWithName: String? = null,
 ) {
     fun makeModuleHeader(): JsIrModuleHeader {
         val nameBindings = mutableMapOf<String, String>()
         val definitions = mutableSetOf<String>()
         val optionalCrossModuleImports = hashSetOf<String>()
-        var hasJsExports = false
+        var hasDeclarationsToReexport = false
         for (fragment in fragments) {
-            hasJsExports = hasJsExports || !fragment.exports.isEmpty
+            hasDeclarationsToReexport = hasDeclarationsToReexport || !fragment.exports.isEmpty
             for ((tag, name) in fragment.nameBindings.entries) {
                 nameBindings[tag] = name.toString()
             }
@@ -52,7 +53,7 @@ class JsIrModule(
             definitions = definitions,
             nameBindings = nameBindings,
             optionalCrossModuleImports = optionalCrossModuleImports,
-            hasJsExports = hasJsExports,
+            reexportedInModuleWithName = reexportedInModuleWithName.takeIf { hasDeclarationsToReexport },
             associatedModule = this
         )
     }
@@ -64,8 +65,8 @@ class JsIrModuleHeader(
     val definitions: Set<String>,
     val nameBindings: Map<String, String>,
     val optionalCrossModuleImports: Set<String>,
-    val hasJsExports: Boolean,
-    var associatedModule: JsIrModule?
+    val reexportedInModuleWithName: String? = null,
+    var associatedModule: JsIrModule?,
 ) {
     val externalNames: Set<String> by lazy(LazyThreadSafetyMode.NONE) { nameBindings.keys - definitions }
 }
@@ -89,19 +90,18 @@ class JsIrProgram(private var modules: List<JsIrModule>) {
     }
 }
 
-class CrossModuleDependenciesResolver(
-    private val moduleKind: ModuleKind,
-    private val headers: List<JsIrModuleHeader>
-) {
+class CrossModuleDependenciesResolver(private val moduleKind: ModuleKind, private val headers: List<JsIrModuleHeader>) {
     fun resolveCrossModuleDependencies(relativeRequirePath: Boolean): Map<JsIrModuleHeader, CrossModuleReferences> {
-        val headerToBuilder = headers.associateWith { JsIrModuleCrossModuleReferenceBuilder(moduleKind, it, relativeRequirePath) }
-        val definitionModule = mutableMapOf<String, JsIrModuleCrossModuleReferenceBuilder>()
-
-        if (moduleKind != ModuleKind.ES) {
-            val mainModuleHeader = headers.last()
-            val otherModuleHeaders = headers.dropLast(1)
-            headerToBuilder[mainModuleHeader]!!.transitiveJsExportFrom = otherModuleHeaders
+        val reexportModuleToHeader = headers.groupBy { it.reexportedInModuleWithName }
+        val headerToBuilder = headers.associateWith {
+            JsIrModuleCrossModuleReferenceBuilder(
+                moduleKind,
+                it,
+                relativeRequirePath,
+                reexportModuleToHeader[it.moduleName] ?: emptyList(),
+            )
         }
+        val definitionModule = mutableMapOf<String, JsIrModuleCrossModuleReferenceBuilder>()
 
         for (header in headers) {
             val builder = headerToBuilder[header]!!
@@ -115,6 +115,7 @@ class CrossModuleDependenciesResolver(
             val builder = headerToBuilder[header]!!
             for (tag in header.externalNames) {
                 val fromModuleBuilder = definitionModule[tag]
+
                 if (fromModuleBuilder == null) {
                     if (tag in header.optionalCrossModuleImports) {
                         continue
@@ -128,6 +129,8 @@ class CrossModuleDependenciesResolver(
             }
         }
 
+        headerToBuilder.forEach { it.value.buildExportNames() }
+
         return headers.associateWith { headerToBuilder[it]!!.buildCrossModuleRefs() }
     }
 }
@@ -137,21 +140,20 @@ private class CrossModuleRef(val module: JsIrModuleCrossModuleReferenceBuilder,
 private class JsIrModuleCrossModuleReferenceBuilder(
     val moduleKind: ModuleKind,
     val header: JsIrModuleHeader,
-    val relativeRequirePath: Boolean
+    val relativeRequirePath: Boolean,
+    val transitiveExportFrom: List<JsIrModuleHeader>,
 ) {
     val imports = mutableListOf<CrossModuleRef>()
     val exports = mutableSetOf<String>()
-    var transitiveJsExportFrom = emptyList<JsIrModuleHeader>()
 
-    private lateinit var exportNames: Map<String, String> // tag -> index
+    lateinit var exportNames: Map<String, String> // tag -> index
 
-    private fun buildExportNames() {
-        var index = 0
+    fun buildExportNames(startIndex: Int = 0) {
+        var index = startIndex
         exportNames = exports.sorted().associateWith { index++.toJsIdentifier() }
     }
 
     fun buildCrossModuleRefs(): CrossModuleReferences {
-        buildExportNames()
         val isImportOptional = moduleKind == ModuleKind.ES
         val importedModules = mutableMapOf<JsIrModuleHeader, JsImportedModule>()
 
@@ -165,18 +167,16 @@ private class JsIrModuleCrossModuleReferenceBuilder(
 
         val resultImports = imports.associate { crossModuleRef ->
             val tag = crossModuleRef.tag
-            require(crossModuleRef.module::exportNames.isInitialized) {
-                // This situation appears in case of a dependent module redefine a symbol (function) from their dependency
-                "Cross module dependency resolution failed due to signature '$tag' redefinition"
-            }
             val exportedAs = crossModuleRef.module.exportNames[tag]!!
             val importedModule = import(crossModuleRef.module.header)
 
             tag to CrossModuleImport(exportedAs, importedModule)
         }
 
-        val transitiveExport = transitiveJsExportFrom.mapNotNull {
-            if (!it.hasJsExports) null else CrossModuleTransitiveExport(import(it).internalName, it.externalModuleName)
+        val transitiveExport = transitiveExportFrom.mapNotNull {
+            it.reexportedInModuleWithName?.run {
+                CrossModuleTransitiveExport(import(it).internalName, relativeRequirePath(it) ?: it.externalModuleName)
+            }
         }
         return CrossModuleReferences(
             moduleKind,
@@ -208,8 +208,7 @@ private class JsIrModuleCrossModuleReferenceBuilder(
             .toRelativeString(parentMain)
             .replace(File.separator, "/")
 
-        return relativePath.takeIf { it.startsWith("../") }
-            ?: "./$relativePath"
+        return relativePath.takeIf { it.startsWith("../") } ?: "./$relativePath"
     }
 }
 
@@ -222,7 +221,7 @@ fun CrossModuleTransitiveExport.getRequireEsmName() = "$externalName$ESM_EXTENSI
 class CrossModuleReferences(
     val moduleKind: ModuleKind,
     val importedModules: List<JsImportedModule>, // additional Kotlin imported modules
-    val transitiveJsExportFrom: List<CrossModuleTransitiveExport>, // the list of modules which provide their js exports for transitive export
+    val transitiveExportFrom: List<CrossModuleTransitiveExport>, // the list of modules which provide their exports for transitive export
     val exports: Map<String, String>, // tag -> index
     val imports: Map<String, CrossModuleImport>, // tag -> import statement
 ) {
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/Merger.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/Merger.kt
index f5eed8d81dd..d6fa6420057 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/Merger.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/Merger.kt
@@ -148,7 +148,6 @@ class Merger(
                 ?.asSequence()
                 ?.flatMap { (it.subject as JsExport.Subject.Elements).elements }
                 ?.distinctBy { it.alias?.ident ?: it.name.ident }
-                ?.map { if (it.name.ident == it.alias?.ident) JsExport.Element(it.name, null) else it }
                 ?.toList()
 
             val oneLargeExportStatement = exportedElements?.let { JsExport(JsExport.Subject.Elements(it)) }
@@ -179,14 +178,14 @@ class Merger(
 
     private fun transitiveJsExport(): List<JsStatement> {
         return if (isEsModules) {
-            crossModuleReferences.transitiveJsExportFrom.map {
+            crossModuleReferences.transitiveExportFrom.map {
                 JsExport(JsExport.Subject.All, it.getRequireEsmName())
             }
         } else {
             val internalModuleName = ReservedJsNames.makeInternalModuleName()
             val exporterName = ReservedJsNames.makeJsExporterName()
 
-            crossModuleReferences.transitiveJsExportFrom.map {
+            crossModuleReferences.transitiveExportFrom.map {
                 JsInvocation(
                     JsNameRef(exporterName, it.internalName.makeRef()),
                     internalModuleName.makeRef()
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/ModuleFragmentToExternalName.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/ModuleFragmentToExternalName.kt
new file mode 100644
index 00000000000..a3c58afa14b
--- /dev/null
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/ModuleFragmentToExternalName.kt
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.ir.backend.js.transformers.irToJs
+
+import org.jetbrains.kotlin.ir.backend.js.utils.getJsName
+import org.jetbrains.kotlin.ir.backend.js.utils.sanitizeName
+import org.jetbrains.kotlin.ir.declarations.IrFile
+import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
+import org.jetbrains.kotlin.ir.declarations.name
+import org.jetbrains.kotlin.ir.declarations.path
+
+private const val EXPORTER_FILE_POSTFIX = ".export"
+
+class ModuleFragmentToExternalName(private val jsOutputNamesMapping: Map<IrModuleFragment, String>) {
+    fun getExternalNameFor(file: IrFile, granularity: JsGenerationGranularity): String {
+        assert(granularity == JsGenerationGranularity.PER_FILE) { "This method should be used only for PER_FILE granularity" }
+        return file.module.getJsOutputName().getExternalModuleNameForPerFile(file)
+    }
+
+    fun getExternalNameForExporterFile(file: IrFile, granularity: JsGenerationGranularity): String {
+        return "${getExternalNameFor(file, granularity)}$EXPORTER_FILE_POSTFIX"
+    }
+
+    fun getSafeNameFor(file: IrFile): String {
+        return "${file.module.safeName}/${file.stableFileName}"
+    }
+
+    fun getSafeNameExporterFor(file: IrFile): String {
+        return "${getSafeNameFor(file)}$EXPORTER_FILE_POSTFIX"
+    }
+
+    fun getExternalNameFor(module: IrModuleFragment): String {
+        return module.getJsOutputName()
+    }
+
+    private fun IrModuleFragment.getJsOutputName(): String {
+        return jsOutputNamesMapping[this] ?: sanitizeName(safeName)
+    }
+
+    private fun String.getExternalModuleNameForPerFile(file: IrFile) = "$this/${file.stableFileName}"
+
+    private val IrFile.stableFileName: String
+        get() {
+            val prefix = packageFqName.asString().replace('.', '/')
+            val fileName = getJsName() ?: name.substringBefore(".kt")
+            return "$prefix${if (prefix.isNotEmpty()) "/" else ""}$fileName"
+        }
+}
\ No newline at end of file
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt
index 8a736a42c91..9d0c28db124 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt
@@ -10,7 +10,6 @@ import org.jetbrains.kotlin.backend.common.lower.BOUND_VALUE_PARAMETER
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.IrFileEntry
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
-import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
 import org.jetbrains.kotlin.ir.backend.js.JsLoweredDeclarationOrigin
 import org.jetbrains.kotlin.ir.backend.js.JsStatementOrigins
 import org.jetbrains.kotlin.ir.backend.js.lower.*
@@ -19,7 +18,6 @@ import org.jetbrains.kotlin.ir.backend.js.utils.*
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
-import org.jetbrains.kotlin.ir.types.isSubtypeOfClass
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
 import org.jetbrains.kotlin.ir.visitors.acceptVoid
@@ -31,6 +29,7 @@ import org.jetbrains.kotlin.js.config.SourceMapNamesPolicy
 import org.jetbrains.kotlin.js.config.SourceMapSourceEmbedding
 import org.jetbrains.kotlin.util.OperatorNameConventions
 import org.jetbrains.kotlin.utils.addIfNotNull
+import org.jetbrains.kotlin.utils.addToStdlib.runIf
 import org.jetbrains.kotlin.utils.memoryOptimizedMap
 import org.jetbrains.kotlin.utils.memoryOptimizedPlus
 import java.io.FileInputStream
@@ -38,8 +37,8 @@ import java.io.IOException
 import java.io.InputStreamReader
 import java.nio.charset.StandardCharsets
 
-fun jsUndefined(context: IrNamer, backendContext: JsIrBackendContext): JsExpression {
-    return when (val void = backendContext.getVoid()) {
+fun jsUndefined(context: JsStaticContext): JsExpression {
+    return when (val void = context.backendContext.getVoid()) {
         is IrGetField -> context.getNameForField(void.symbol.owner).makeRef()
         else -> JsNullLiteral()
     }
@@ -93,15 +92,11 @@ fun objectCreate(prototype: JsExpression, context: JsStaticContext) =
     )
 
 fun defineProperty(obj: JsExpression, name: String, getter: JsExpression?, setter: JsExpression?, context: JsStaticContext): JsExpression {
-    val undefined by lazy(LazyThreadSafetyMode.NONE) { jsUndefined(context, context.backendContext) }
     return JsInvocation(
         context
             .getNameForStaticFunction(context.backendContext.intrinsics.jsDefinePropertySymbol.owner)
             .makeRef(),
-        obj,
-        JsStringLiteral(name),
-        getter ?: undefined,
-        setter ?: undefined
+        listOfNotNull(obj, JsStringLiteral(name), getter ?: runIf(setter != null) { jsUndefined(context) }, setter)
     )
 }
 
@@ -213,7 +208,7 @@ fun translateCall(
             val nameForStaticDeclaration = context.getNameForStaticDeclaration(target)
             JsNameRef(Namer.CALL_FUNCTION, JsNameRef(nameForStaticDeclaration))
         } else {
-            val qualifierName = context.getNameForClass(klass).makeRef()
+            val qualifierName = klass.getClassRef(context.staticContext)
             val targetName = context.getNameForMemberFunction(target)
             val qPrototype = JsNameRef(targetName, prototypeOf(qualifierName, context.staticContext))
             JsNameRef(Namer.CALL_FUNCTION, qPrototype)
@@ -399,7 +394,7 @@ fun translateCallArguments(
     val varargParameterIndex = function.realOverrideTarget.varargParameterIndex()
 
     val validWithNullArgs = expression.validWithNullArgs()
-    val jsUndefined by lazy(LazyThreadSafetyMode.NONE) { jsUndefined(context, context.staticContext.backendContext) }
+    val jsUndefined by lazy(LazyThreadSafetyMode.NONE) { jsUndefined(context.staticContext) }
 
     val arguments = (0 until size)
         .mapIndexedTo(ArrayList(size)) { i, _ ->
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/resolveTemporaryNames.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/resolveTemporaryNames.kt
index 90e12b50f2e..a6263f56030 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/resolveTemporaryNames.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/resolveTemporaryNames.kt
@@ -41,7 +41,7 @@ private fun JsNode.resolveNames(): Map<JsName, JsName> {
         for (temporaryName in scope.declaredNames.asSequence().filter { it.isTemporary }) {
             var resolvedName = temporaryName.ident
             var suffix = nextSuffix.getOrDefault(temporaryName.ident, 0)
-            while (resolvedName in JsDeclarationScope.RESERVED_WORDS || !occupiedNames.add(resolvedName)) {
+            while (resolvedName in JsDeclarationScope.RESERVED_WORDS || resolvedName in occupiedNames) {
                 resolvedName = "${temporaryName.ident}_${suffix++}"
             }
             nextSuffix[temporaryName.ident] = suffix
@@ -79,6 +79,7 @@ private fun JsNode.computeScopes(): Scope {
             // We need it to not rename methods and fields inside class body
             // Because if they are in clash with something, it means overriding
             x.constructor?.accept(this)
+            x.baseClass?.accept(this)
             x.members.forEach { visitFunction(it, shouldReserveName = false) }
         }
 
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/IrTypeUtils.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/IrTypeUtils.kt
index 3f28cd5172a..14681256ffe 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/IrTypeUtils.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/IrTypeUtils.kt
@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.ir.backend.js.utils
 
 import org.jetbrains.kotlin.ir.declarations.IrClass
+import org.jetbrains.kotlin.ir.declarations.IrConstructor
 import org.jetbrains.kotlin.ir.declarations.IrDeclarationWithName
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.symbols.IrClassifierSymbol
@@ -14,10 +15,12 @@ import org.jetbrains.kotlin.ir.symbols.IrTypeParameterSymbol
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.fqNameWhenAvailable
 import org.jetbrains.kotlin.ir.util.isEffectivelyExternal
+import org.jetbrains.kotlin.js.backend.ast.JsExpression
+import org.jetbrains.kotlin.js.backend.ast.JsInvocation
 import org.jetbrains.kotlin.ir.util.unexpectedSymbolKind
-import org.jetbrains.kotlin.js.backend.ast.JsNameRef
 import org.jetbrains.kotlin.types.Variance
 import org.jetbrains.kotlin.utils.addToStdlib.ifNotEmpty
+import org.jetbrains.kotlin.utils.addToStdlib.butIf
 
 fun IrType.asString(): String = when (this) {
     // TODO: should each IrErrorType have own string representation?
@@ -54,13 +57,24 @@ tailrec fun erase(type: IrType): IrClass? = when (val classifier = type.classifi
     is IrScriptSymbol -> null
 }
 
-fun IrType.getClassRef(context: JsGenerationContext): JsNameRef =
-    when (val klass = classifierOrFail.owner) {
-        is IrClass ->
-            if (klass.isEffectivelyExternal())
-                context.getRefForExternalClass(klass)
-            else
-                context.getNameForClass(klass).makeRef()
-
+fun IrType.getClassRef(context: JsStaticContext): JsExpression {
+    return when (val klass = classifierOrFail.owner) {
+        is IrClass -> klass.getClassRef(context)
         else -> context.getNameForStaticDeclaration(klass as IrDeclarationWithName).makeRef()
     }
+}
+
+fun IrClass.getClassRef(context: JsStaticContext): JsExpression {
+    return when {
+        isEffectivelyExternal() -> context.getRefForExternalClass(this)
+        else -> context.getNameForClass(this)
+            .makeRef()
+            .butIf(context.isPerFile) { JsInvocation(it) }
+    }
+}
+
+fun IrConstructor.getConstructorRef(context: JsStaticContext): JsExpression {
+    return context.getNameForConstructor(this)
+        .makeRef()
+        .butIf(context.isPerFile && !isEffectivelyExternal()) { JsInvocation(it) }
+}
\ No newline at end of file
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/JsStaticContext.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/JsStaticContext.kt
index 49a16f996d6..bd52fbe754a 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/JsStaticContext.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/JsStaticContext.kt
@@ -6,8 +6,10 @@
 package org.jetbrains.kotlin.ir.backend.js.utils
 
 import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
+import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsIntrinsicTransformers
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsIrClassModel
+import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.TranslationMode
 import org.jetbrains.kotlin.ir.declarations.IrDeclaration
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.js.backend.ast.JsCompositeBlock
@@ -17,9 +19,12 @@ class JsStaticContext(
     val backendContext: JsIrBackendContext,
     private val irNamer: IrNamer,
     val globalNameScope: NameTable<IrDeclaration>,
+    val mode: TranslationMode,
 ) : IrNamer by irNamer {
     val intrinsics = JsIntrinsicTransformers(backendContext)
     val classModels = mutableMapOf<IrClassSymbol, JsIrClassModel>()
 
     val initializerBlock = JsCompositeBlock()
+
+    val isPerFile: Boolean get() = mode.granularity === JsGenerationGranularity.PER_FILE
 }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/Keeper.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/Keeper.kt
index c4ede90608c..6b6cc6ddb98 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/Keeper.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/Keeper.kt
@@ -14,7 +14,8 @@ class Keeper(private val keep: Set<String>) : IrElementVisitor<Unit, Keeper.Keep
     private val keptDeclarations: MutableSet<IrDeclaration> = mutableSetOf()
 
     fun shouldKeep(declaration: IrDeclaration): Boolean {
-        return declaration in keptDeclarations
+        return declaration in keptDeclarations ||
+                (declaration is IrOverridableDeclaration<*> && declaration.overriddenSymbols.any { shouldKeep(it.owner as IrDeclaration) })
     }
 
     override fun visitElement(element: IrElement, data: KeepData) {
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/serialization/JsIrAstDeserializer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/serialization/JsIrAstDeserializer.kt
index 32b10f31d48..070a5bb83ab 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/serialization/JsIrAstDeserializer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/serialization/JsIrAstDeserializer.kt
@@ -14,8 +14,8 @@ import org.jetbrains.kotlin.js.backend.ast.metadata.*
 import java.nio.ByteBuffer
 import java.util.*
 
-fun deserializeJsIrProgramFragment(input: ByteArray): JsIrProgramFragment {
-    return JsIrAstDeserializer(input).readFragment()
+fun deserializeJsIrProgramFragment(input: ByteArray): List<JsIrProgramFragment> {
+    return JsIrAstDeserializer(input).readFragments()
 }
 
 private class JsIrAstDeserializer(private val source: ByteArray) {
@@ -76,6 +76,10 @@ private class JsIrAstDeserializer(private val source: ByteArray) {
         return if (readBoolean()) then() else null
     }
 
+    fun readFragments(): List<JsIrProgramFragment> {
+        return readList { readFragment() }
+    }
+
     fun readFragment(): JsIrProgramFragment {
         return JsIrProgramFragment(readString()).apply {
             readRepeated {
@@ -320,7 +324,7 @@ private class JsIrAstDeserializer(private val source: ByteArray) {
                         CLASS -> {
                             JsClass(
                                 ifTrue { nameTable[readInt()] },
-                                ifTrue { nameTable[readInt()].makeRef() },
+                                ifTrue { readExpression() },
                                 ifTrue { readFunction() },
                             ).apply {
                                 readRepeated { members += readFunction() }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/serialization/JsIrAstSerializer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/serialization/JsIrAstSerializer.kt
index af555b289e8..afdb830386c 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/serialization/JsIrAstSerializer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/serialization/JsIrAstSerializer.kt
@@ -15,8 +15,8 @@ import java.io.DataOutputStream
 import java.io.OutputStream
 import java.util.*
 
-fun JsIrProgramFragment.serializeTo(output: OutputStream) {
-    JsIrAstSerializer().append(this).saveTo(output)
+fun List<JsIrProgramFragment>.serializeTo(output: OutputStream) {
+    JsIrAstSerializer().appendAll(this).saveTo(output)
 }
 
 private class DataWriter {
@@ -89,6 +89,12 @@ private class JsIrAstSerializer {
     private val fileStack: Deque<String> = ArrayDeque()
     private val importedNames = mutableSetOf<JsName>()
 
+    fun appendAll(fragments: List<JsIrProgramFragment>): JsIrAstSerializer {
+        fragmentSerializer.writeInt(fragments.size)
+        fragments.forEach(::append)
+        return this
+    }
+
     fun append(fragment: JsIrProgramFragment): JsIrAstSerializer {
         importedNames += fragment.imports.map { fragment.nameBindings[it.key]!! }
         fragmentSerializer.writeFragment(fragment)
@@ -437,9 +443,8 @@ private class JsIrAstSerializer {
                 ifNotNull(x.name) {
                     writeInt(internalizeName(it))
                 }
-                // TODO: add more complex JsNameRef parsing in future when we will support `class` expressions inside a `js` call
-                ifNotNull(x.baseClass?.name) {
-                    writeInt(internalizeName(it))
+                ifNotNull(x.baseClass) {
+                    writeExpression(it)
                 }
                 ifNotNull(x.constructor) {
                     writeFunction(it)
diff --git a/compiler/testData/cli/js/perFileWithValidModuleKind.args b/compiler/testData/cli/js/perFileWithValidModuleKind.args
new file mode 100644
index 00000000000..abb8af0e440
--- /dev/null
+++ b/compiler/testData/cli/js/perFileWithValidModuleKind.args
@@ -0,0 +1,9 @@
+$TESTDATA_DIR$/simple2js.kt
+-Xir-only
+-ir-output-dir
+$TEMP_DIR$
+-ir-output-name
+out
+-module-kind
+es
+-Xir-per-file
diff --git a/compiler/testData/cli/js/perFileWithValidModuleKind.out b/compiler/testData/cli/js/perFileWithValidModuleKind.out
new file mode 100644
index 00000000000..a0aba9318ad
--- /dev/null
+++ b/compiler/testData/cli/js/perFileWithValidModuleKind.out
@@ -0,0 +1 @@
+OK
\ No newline at end of file
diff --git a/compiler/testData/cli/js/perFileWithWrongModuleKind.args b/compiler/testData/cli/js/perFileWithWrongModuleKind.args
new file mode 100644
index 00000000000..7594c96598b
--- /dev/null
+++ b/compiler/testData/cli/js/perFileWithWrongModuleKind.args
@@ -0,0 +1,9 @@
+$TESTDATA_DIR$/simple2js.kt
+-Xir-only
+-ir-output-dir
+$TEMP_DIR$
+-ir-output-name
+out
+-module-kind
+commonjs
+-Xir-per-file
diff --git a/compiler/testData/cli/js/perFileWithWrongModuleKind.out b/compiler/testData/cli/js/perFileWithWrongModuleKind.out
new file mode 100644
index 00000000000..0c1fcfa2050
--- /dev/null
+++ b/compiler/testData/cli/js/perFileWithWrongModuleKind.out
@@ -0,0 +1,2 @@
+error: per-file compilation can't be used with any `moduleKind` except `es` (ECMAScript Modules)
+COMPILATION_ERROR
diff --git a/compiler/tests-common-new/tests/org/jetbrains/kotlin/test/services/configuration/JsEnvironmentConfigurator.kt b/compiler/tests-common-new/tests/org/jetbrains/kotlin/test/services/configuration/JsEnvironmentConfigurator.kt
index 4536a7207d0..e33dc4784d5 100644
--- a/compiler/tests-common-new/tests/org/jetbrains/kotlin/test/services/configuration/JsEnvironmentConfigurator.kt
+++ b/compiler/tests-common-new/tests/org/jetbrains/kotlin/test/services/configuration/JsEnvironmentConfigurator.kt
@@ -58,7 +58,9 @@ class JsEnvironmentConfigurator(testServices: TestServices) : EnvironmentConfigu
             TranslationMode.FULL_DEV to "out",
             TranslationMode.FULL_PROD_MINIMIZED_NAMES to "outMin",
             TranslationMode.PER_MODULE_DEV to "outPm",
-            TranslationMode.PER_MODULE_PROD_MINIMIZED_NAMES to "outPmMin"
+            TranslationMode.PER_MODULE_PROD_MINIMIZED_NAMES to "outPmMin",
+            TranslationMode.PER_FILE_DEV to "outPf",
+            TranslationMode.PER_FILE_PROD_MINIMIZED_NAMES to "outPfMin"
         )
 
         private const val OUTPUT_KLIB_DIR_NAME = "outputKlibDir"
@@ -86,11 +88,15 @@ class JsEnvironmentConfigurator(testServices: TestServices) : EnvironmentConfigu
         }
 
         fun getJsModuleArtifactPath(testServices: TestServices, moduleName: String, translationMode: TranslationMode = TranslationMode.FULL_DEV): String {
-            return getJsArtifactsOutputDir(testServices, translationMode).absolutePath + File.separator + getJsArtifactSimpleName(testServices, moduleName) + "_v5"
+            return getJsArtifactsOutputDir(testServices, translationMode).absolutePath + File.separator + getJsModuleArtifactName(testServices, moduleName)
         }
 
         fun getRecompiledJsModuleArtifactPath(testServices: TestServices, moduleName: String, translationMode: TranslationMode = TranslationMode.FULL_DEV): String {
-            return getJsArtifactsRecompiledOutputDir(testServices, translationMode).absolutePath + File.separator + getJsArtifactSimpleName(testServices, moduleName) + "_v5"
+            return getJsArtifactsRecompiledOutputDir(testServices, translationMode).absolutePath + File.separator + getJsModuleArtifactName(testServices, moduleName)
+        }
+
+        fun getJsModuleArtifactName(testServices: TestServices, moduleName: String): String {
+           return getJsArtifactSimpleName(testServices, moduleName) + "_v5"
         }
 
         fun getJsKlibArtifactPath(testServices: TestServices, moduleName: String): String {
diff --git a/compiler/tests-common-new/tests/org/jetbrains/kotlin/test/services/impl/TemporaryDirectoryManagerImpl.kt b/compiler/tests-common-new/tests/org/jetbrains/kotlin/test/services/impl/TemporaryDirectoryManagerImpl.kt
index 24eb6913ace..acf19173a04 100644
--- a/compiler/tests-common-new/tests/org/jetbrains/kotlin/test/services/impl/TemporaryDirectoryManagerImpl.kt
+++ b/compiler/tests-common-new/tests/org/jetbrains/kotlin/test/services/impl/TemporaryDirectoryManagerImpl.kt
@@ -26,10 +26,9 @@ class TemporaryDirectoryManagerImpl(testServices: TestServices) : TemporaryDirec
 
         // This code will simplify directory name for windows. This is needed because there can occur errors due to long name
         val lastDot = className.lastIndexOf('.')
-        val packageName = className.substring(0, lastDot + 1)
         val simplifiedClassName = className.substring(lastDot + 1).getOnlyUpperCaseSymbols()
         val simplifiedMethodName = methodName.getOnlyUpperCaseSymbols()
-        KtTestUtil.tmpDirForTest(packageName + simplifiedClassName, "test$simplifiedMethodName")
+        KtTestUtil.tmpDirForTest(simplifiedClassName, simplifiedMethodName)
     }
 
     override val rootDir: File
diff --git a/compiler/tests-gen/org/jetbrains/kotlin/cli/CliTestGenerated.java b/compiler/tests-gen/org/jetbrains/kotlin/cli/CliTestGenerated.java
index a4f51ff2d8e..27187f6bc49 100644
--- a/compiler/tests-gen/org/jetbrains/kotlin/cli/CliTestGenerated.java
+++ b/compiler/tests-gen/org/jetbrains/kotlin/cli/CliTestGenerated.java
@@ -1403,6 +1403,16 @@ public class CliTestGenerated extends AbstractCliTest {
             runTest("compiler/testData/cli/js/outputPrefixFileNotFound.args");
         }
 
+        @TestMetadata("perFileWithValidModuleKind.args")
+        public void testPerFileWithValidModuleKind() throws Exception {
+            runTest("compiler/testData/cli/js/perFileWithValidModuleKind.args");
+        }
+
+        @TestMetadata("perFileWithWrongModuleKind.args")
+        public void testPerFileWithWrongModuleKind() throws Exception {
+            runTest("compiler/testData/cli/js/perFileWithWrongModuleKind.args");
+        }
+
         @TestMetadata("reifiedIntersectionType.args")
         public void testReifiedIntersectionType() throws Exception {
             runTest("compiler/testData/cli/js/reifiedIntersectionType.args");
diff --git a/core/util.runtime/src/org/jetbrains/kotlin/utils/addToStdlib.kt b/core/util.runtime/src/org/jetbrains/kotlin/utils/addToStdlib.kt
index ee925e164aa..ef56069fdaa 100644
--- a/core/util.runtime/src/org/jetbrains/kotlin/utils/addToStdlib.kt
+++ b/core/util.runtime/src/org/jetbrains/kotlin/utils/addToStdlib.kt
@@ -218,6 +218,8 @@ inline fun <T, R> Iterable<T>.same(extractor: (T) -> R): Boolean {
 inline fun <R> runIf(condition: Boolean, block: () -> R): R? = if (condition) block() else null
 inline fun <R> runUnless(condition: Boolean, block: () -> R): R? = if (condition) null else block()
 
+inline fun <A : B, B> A.butIf(condition: Boolean, block: (A) -> B): B = if (condition) block(this) else this
+
 inline fun <T, R> Collection<T>.foldMap(transform: (T) -> R, operation: (R, R) -> R): R {
     val iterator = iterator()
     var result = transform(iterator.next())
diff --git a/js/js.ast/src/org/jetbrains/kotlin/js/backend/ast/JsClass.kt b/js/js.ast/src/org/jetbrains/kotlin/js/backend/ast/JsClass.kt
index 01cb6ce103a..d54eb006d06 100644
--- a/js/js.ast/src/org/jetbrains/kotlin/js/backend/ast/JsClass.kt
+++ b/js/js.ast/src/org/jetbrains/kotlin/js/backend/ast/JsClass.kt
@@ -9,7 +9,7 @@ import org.jetbrains.kotlin.js.common.Symbol
 
 class JsClass(
     private var name: JsName? = null,
-    var baseClass: JsNameRef? = null,
+    var baseClass: JsExpression? = null,
     var constructor: JsFunction? = null,
     val members: MutableList<JsFunction> = mutableListOf()
 ) : JsLiteral(), HasName {
diff --git a/js/js.ast/src/org/jetbrains/kotlin/js/backend/ast/JsExport.kt b/js/js.ast/src/org/jetbrains/kotlin/js/backend/ast/JsExport.kt
index e8123616981..7896989c272 100644
--- a/js/js.ast/src/org/jetbrains/kotlin/js/backend/ast/JsExport.kt
+++ b/js/js.ast/src/org/jetbrains/kotlin/js/backend/ast/JsExport.kt
@@ -18,10 +18,7 @@ class JsExport(
         object All : Subject()
     }
 
-    class Element(
-        val name: JsNameRef,
-        val alias: JsName?
-    )
+    class Element(val name: JsNameRef, val alias: JsName? = null)
 
     override fun accept(visitor: JsVisitor) {
         visitor.visitExport(this)
diff --git a/js/js.tests/test/org/jetbrains/kotlin/incremental/AbstractInvalidationTest.kt b/js/js.tests/test/org/jetbrains/kotlin/incremental/AbstractInvalidationTest.kt
index 68fc25f91f4..302ec6f3c77 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/incremental/AbstractInvalidationTest.kt
+++ b/js/js.tests/test/org/jetbrains/kotlin/incremental/AbstractInvalidationTest.kt
@@ -23,11 +23,11 @@ import org.jetbrains.kotlin.config.languageVersionSettings
 import org.jetbrains.kotlin.ir.backend.js.JsIrCompilerWithIC
 import org.jetbrains.kotlin.ir.backend.js.SourceMapsInfo
 import org.jetbrains.kotlin.ir.backend.js.WholeWorldStageController
-import org.jetbrains.kotlin.ir.backend.js.codegen.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.ic.*
 import org.jetbrains.kotlin.ir.backend.js.jsPhases
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.CompilationOutputs
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.extension
+import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.safeModuleName
 import org.jetbrains.kotlin.ir.declarations.impl.IrFactoryImplForJsIC
 import org.jetbrains.kotlin.js.config.JSConfigurationKeys
@@ -361,7 +361,7 @@ abstract class AbstractInvalidationTest(private val targetBackend: TargetBackend
                     relativeRequirePath = true
                 )
 
-                val (jsOutput, rebuiltModules) = jsExecutableProducer.buildExecutable(multiModule = true, outJsProgram = true)
+                val (jsOutput, rebuiltModules) = jsExecutableProducer.buildExecutable(granularity = JsGenerationGranularity.PER_MODULE, outJsProgram = true)
                 val writtenFiles = writeJsCode(projStep.id, mainModuleName, jsOutput)
 
                 verifyJsExecutableProducerBuildModules(projStep.id, rebuiltModules, projStep.dirtyJS)
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/converters/JsIrBackendFacade.kt b/js/js.tests/test/org/jetbrains/kotlin/js/test/converters/JsIrBackendFacade.kt
index 4ad3fec7801..149612cb351 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/converters/JsIrBackendFacade.kt
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/converters/JsIrBackendFacade.kt
@@ -13,11 +13,11 @@ import org.jetbrains.kotlin.cli.common.isWindows
 import org.jetbrains.kotlin.config.CommonConfigurationKeys
 import org.jetbrains.kotlin.config.CompilerConfiguration
 import org.jetbrains.kotlin.ir.backend.js.*
-import org.jetbrains.kotlin.ir.backend.js.codegen.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.ic.JsExecutableProducer
 import org.jetbrains.kotlin.ir.backend.js.lower.serialization.ir.JsManglerDesc
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.*
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
+import org.jetbrains.kotlin.ir.backend.js.SourceMapsInfo
 import org.jetbrains.kotlin.ir.declarations.impl.IrFactoryImplForJsIC
 import org.jetbrains.kotlin.ir.linkage.partial.PartialLinkageConfig
 import org.jetbrains.kotlin.ir.linkage.partial.PartialLinkageLogLevel
@@ -54,10 +54,10 @@ class JsIrBackendFacade(
     val testServices: TestServices,
     private val firstTimeCompilation: Boolean
 ) : AbstractTestFacade<BinaryArtifacts.KLib, BinaryArtifacts.Js>() {
-    override val inputKind: ArtifactKinds.KLib
-        get() = ArtifactKinds.KLib
-    override val outputKind: ArtifactKinds.Js
-        get() = ArtifactKinds.Js
+    override val inputKind: ArtifactKinds.KLib get() = ArtifactKinds.KLib
+    override val outputKind: ArtifactKinds.Js get() = ArtifactKinds.Js
+
+    private val jsIrPathReplacer by lazy { JsIrPathReplacer(testServices) }
 
     constructor(testServices: TestServices) : this(testServices, firstTimeCompilation = true)
 
@@ -90,8 +90,8 @@ class JsIrBackendFacade(
 
         val granularity = when {
             !firstTimeCompilation -> JsGenerationGranularity.WHOLE_PROGRAM
+            splitPerFile || module.kind == ModuleKind.ES -> JsGenerationGranularity.PER_FILE
             splitPerModule || perModule -> JsGenerationGranularity.PER_MODULE
-            splitPerFile -> JsGenerationGranularity.PER_FILE
             else -> JsGenerationGranularity.WHOLE_PROGRAM
         }
 
@@ -116,7 +116,7 @@ class JsIrBackendFacade(
                         caches = testServices.jsIrIncrementalDataProvider.getCaches(),
                         relativeRequirePath = false
                     )
-                    jsExecutableProducer.buildExecutable(it.perModule, true).compilationOut
+                    jsExecutableProducer.buildExecutable(it.granularity, true).compilationOut
                 }
             )
             return BinaryArtifacts.Js.JsIrArtifact(
@@ -168,6 +168,7 @@ class JsIrBackendFacade(
         val runIrDce = JsEnvironmentConfigurationDirectives.RUN_IR_DCE in module.directives
         val onlyIrDce = JsEnvironmentConfigurationDirectives.ONLY_IR_DCE in module.directives
         val perModuleOnly = JsEnvironmentConfigurationDirectives.SPLIT_PER_MODULE in module.directives
+        val perFileOnly = JsEnvironmentConfigurationDirectives.SPLIT_PER_FILE in module.directives
         val isEsModules = JsEnvironmentConfigurationDirectives.ES_MODULES in module.directives ||
                 module.directives[JsEnvironmentConfigurationDirectives.MODULE_KIND].contains(ModuleKind.ES)
 
@@ -182,7 +183,7 @@ class JsIrBackendFacade(
             mainArguments,
             moduleToName = runIf(isEsModules) {
                 loweredIr.allModules.associateWith {
-                    "./${getJsArtifactSimpleName(testServices, it.safeName)}_v5.mjs".minifyIfNeed()
+                    "./${getJsArtifactSimpleName(testServices, it.safeName)}_v5".minifyIfNeed()
                 }
             } ?: emptyMap()
         )
@@ -190,17 +191,21 @@ class JsIrBackendFacade(
         // If perModuleOnly then skip whole program
         // (it.dce => runIrDce) && (perModuleOnly => it.perModule)
         val translationModes = TranslationMode.values()
-            .filter { (it.production || !onlyIrDce) && (!it.production || runIrDce) && (!perModuleOnly || it.perModule) }
+            .filter {
+                (it.production || !onlyIrDce) &&
+                        (!it.production || runIrDce) &&
+                        (!perModuleOnly || it.granularity == JsGenerationGranularity.PER_MODULE) &&
+                        (!perFileOnly || it.granularity == JsGenerationGranularity.PER_FILE)
+            }
             .filter { it.production == it.minimizedMemberNames }
+            .filter { isEsModules || it.granularity != JsGenerationGranularity.PER_FILE }
             .toSet()
-        val compilationOut = transformer.generateModule(loweredIr.allModules, translationModes, false)
+        val compilationOut = transformer.generateModule(loweredIr.allModules, translationModes, isEsModules)
         return BinaryArtifacts.Js.JsIrArtifact(outputFile, compilationOut).dump(module)
     }
 
     private fun IrModuleFragment.resolveTestPaths() {
-        JsIrPathReplacer(testServices).let {
-            files.forEach(it::lower)
-        }
+        files.forEach(jsIrPathReplacer::lower)
     }
 
     private fun loadIrFromKlib(module: TestModule, configuration: CompilerConfiguration): IrModuleInfo {
@@ -268,8 +273,9 @@ class JsIrBackendFacade(
         return this
     }
 
-    fun File.fixJsFile(newJsTarget: File, moduleId: String, moduleKind: ModuleKind) {
+    fun File.fixJsFile(rootDir: File, newJsTarget: File, moduleId: String, moduleKind: ModuleKind) {
         val newJsCode = ClassicJsBackendFacade.wrapWithModuleEmulationMarkers(readText(), moduleKind, moduleId)
+        val jsCodeWithCorrectImportPath = jsIrPathReplacer.replacePathTokensWithRealPath(newJsCode, newJsTarget, rootDir)
 
         val oldJsMap = File("$absolutePath.map")
         val jsCodeMap = (moduleKind == ModuleKind.PLAIN && oldJsMap.exists()).ifTrue { oldJsMap.readText() }
@@ -277,12 +283,13 @@ class JsIrBackendFacade(
         this.delete()
         oldJsMap.delete()
 
-        newJsTarget.write(newJsCode)
+        newJsTarget.write(jsCodeWithCorrectImportPath)
         jsCodeMap?.let { File("${newJsTarget.absolutePath}.map").write(it) }
     }
 
     private fun CompilationOutputs.writeTo(outputFile: File, moduleId: String, moduleKind: ModuleKind) {
-        val tmpBuildDir = outputFile.parentFile.resolve("tmp-build")
+        val rootDir = outputFile.parentFile
+        val tmpBuildDir = rootDir.resolve("tmp-build")
         // CompilationOutputs keeps the `outputDir` clean by removing all outdated JS and other unknown files.
         // To ensure that useful files around `outputFile`, such as irdump, are not removed, use `tmpBuildDir` instead.
         val allJsFiles = writeAll(tmpBuildDir, outputFile.nameWithoutExtension, false, moduleId, moduleKind).filter {
@@ -290,11 +297,11 @@ class JsIrBackendFacade(
         }
 
         val mainModuleFile = allJsFiles.last()
-        mainModuleFile.fixJsFile(outputFile, moduleId, moduleKind)
+        mainModuleFile.fixJsFile(rootDir, outputFile, moduleId, moduleKind)
 
         dependencies.map { it.first }.zip(allJsFiles.dropLast(1)).forEach { (depModuleId, builtJsFilePath) ->
             val newFile = outputFile.augmentWithModuleName(depModuleId)
-            builtJsFilePath.fixJsFile(newFile, depModuleId, moduleKind)
+            builtJsFilePath.fixJsFile(rootDir, newFile, depModuleId, moduleKind)
         }
         tmpBuildDir.deleteRecursively()
     }
@@ -347,8 +354,9 @@ fun String.minifyIfNeed(): String {
     if (fileName.length <= 80) return this
 
     val fileExtension = fileFullName.substringAfterLast('.')
+    val extensionPart = if (fileExtension.isEmpty()) "" else ".$fileExtension"
 
-    return "$directoryPath$delimiter${fileName.cityHash64().toULong().toString(16)}.$fileExtension"
+    return "$directoryPath$delimiter${fileName.cityHash64().toULong().toString(16)}$extensionPart"
 }
 
 fun File.augmentWithModuleName(moduleName: String): File = File(absolutePath.augmentWithModuleName(moduleName))
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/converters/JsIrPathReplacer.kt b/js/js.tests/test/org/jetbrains/kotlin/js/test/converters/JsIrPathReplacer.kt
index db5b03edb8e..44fed9935b6 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/converters/JsIrPathReplacer.kt
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/converters/JsIrPathReplacer.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -18,6 +18,10 @@ import org.jetbrains.kotlin.test.services.TestServices
 import org.jetbrains.kotlin.test.services.isJsFile
 import org.jetbrains.kotlin.test.services.isMjsFile
 import org.jetbrains.kotlin.test.services.moduleStructure
+import java.io.File
+import kotlin.io.invariantSeparatorsPath
+
+private const val PATH_TO_ROOT_TOKEN = "@PATH_TO_ROOT"
 
 class JsIrPathReplacer(testServices: TestServices) : DeclarationTransformer {
     private val replacements = testServices.collectReplacementsMap()
@@ -35,6 +39,7 @@ class JsIrPathReplacer(testServices: TestServices) : DeclarationTransformer {
 
     private fun IrAnnotationContainer.replaceJsModulePath() {
         val jsModuleAnnotation = getAnnotation(JsAnnotations.jsModuleFqn) ?: return
+
         @Suppress("UNCHECKED_CAST")
         val stringLiteral = jsModuleAnnotation.getValueArgument(0) as IrConst<String>
         val pathReplacement = stringLiteral.getReplacement() ?: return
@@ -43,17 +48,24 @@ class JsIrPathReplacer(testServices: TestServices) : DeclarationTransformer {
     }
 
     private fun IrConst<String>.getReplacement(): IrConst<String>? {
-        val replacement = replacements[value] ?: replacements[value.replace("./", "")] ?: return null
-        return IrConstImpl.string(startOffset, endOffset, type, "./" + replacement.replace("./", ""))
+        return IrConstImpl.string(startOffset, endOffset, type, replacements[value] ?: return null)
     }
 
     private fun TestServices.collectReplacementsMap(): Map<String, String> {
         return moduleStructure.modules.asSequence()
             .map { module -> module to module.files.filter { it.isJsFile || it.isMjsFile } }
             .filter { (_, files) -> files.isNotEmpty() }
-            .flatMap { (module, files) ->  files.map { it.relativePath to module.getNameFor(it, this) } }
-            .plus(getAdditionalFiles(this).map { it.name to it.name })
-            .plus(getAdditionalMainFiles(this).map { it.name to it.name })
+            .flatMap { (module, files) -> files.map { "./${it.relativePath}" to "$PATH_TO_ROOT_TOKEN/${module.getNameFor(it, this)}" } }
+            .plus(getAdditionalFiles(this).map { "./${it.name}" to "$PATH_TO_ROOT_TOKEN/${it.name}" })
+            .plus(getAdditionalMainFiles(this).map { "./${it.name}" to "$PATH_TO_ROOT_TOKEN/${it.name}" })
             .toMap()
     }
-}
\ No newline at end of file
+
+    fun replacePathTokensWithRealPath(content: String, file: File, rootDir: File): String {
+        val relativePathToRootDir = rootDir.relativeTo(file.parentFile).invariantSeparatorsPath.ifEmpty { "." }
+        return content.replace("from '$PATH_TO_ROOT_TOKEN/(.+?)';${'$'}".toRegex(RegexOption.MULTILINE)) { result ->
+            val importPath = result.groups[1]?.value ?: error("Unexpected import path")
+            "from '$relativePathToRootDir/$importPath'\n"
+        }
+    }
+}
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/handlers/JsArtifactsDumpHandler.kt b/js/js.tests/test/org/jetbrains/kotlin/js/test/handlers/JsArtifactsDumpHandler.kt
index 1d87c97b59f..8f28dc5bb3f 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/handlers/JsArtifactsDumpHandler.kt
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/handlers/JsArtifactsDumpHandler.kt
@@ -31,17 +31,23 @@ class JsArtifactsDumpHandler(testServices: TestServices) : AfterAnalysisChecker(
         val testGroupOutputDirForMinification = File(pathToRootOutputDir + "out-min/" + testGroupOutputDirPrefix)
         val testGroupOutputDirForPerModuleCompilation = File(pathToRootOutputDir + "out-per-module/" + testGroupOutputDirPrefix)
         val testGroupOutputDirForPerModuleMinification = File(pathToRootOutputDir + "out-per-module-min/" + testGroupOutputDirPrefix)
+        val testGroupOutputDirForPerFileCompilation = File(pathToRootOutputDir + "out-per-file/" + testGroupOutputDirPrefix)
+        val testGroupOutputDirForPerFileMinification = File(pathToRootOutputDir + "out-per-file-min/" + testGroupOutputDirPrefix)
 
         val outputDir = getOutputDir(originalFile, testGroupOutputDirForCompilation, stopFile)
         val dceOutputDir = getOutputDir(originalFile, testGroupOutputDirForMinification, stopFile)
         val perModuleOutputDir = getOutputDir(originalFile, testGroupOutputDirForPerModuleCompilation, stopFile)
-        val preModuleDceOutputDir = getOutputDir(originalFile, testGroupOutputDirForPerModuleMinification, stopFile)
+        val perModuleDceOutputDir = getOutputDir(originalFile, testGroupOutputDirForPerModuleMinification, stopFile)
+        val perFileOutputDir = getOutputDir(originalFile, testGroupOutputDirForPerFileCompilation, stopFile)
+        val perFileDceOutputDir = getOutputDir(originalFile, testGroupOutputDirForPerFileMinification, stopFile)
         val minOutputDir = File(dceOutputDir, originalFile.nameWithoutExtension)
 
         copy(JsEnvironmentConfigurator.getJsArtifactsOutputDir(testServices), outputDir)
         copy(JsEnvironmentConfigurator.getJsArtifactsOutputDir(testServices, TranslationMode.FULL_PROD_MINIMIZED_NAMES), dceOutputDir)
         copy(JsEnvironmentConfigurator.getJsArtifactsOutputDir(testServices, TranslationMode.PER_MODULE_DEV), perModuleOutputDir)
-        copy(JsEnvironmentConfigurator.getJsArtifactsOutputDir(testServices, TranslationMode.PER_MODULE_PROD_MINIMIZED_NAMES), preModuleDceOutputDir)
+        copy(JsEnvironmentConfigurator.getJsArtifactsOutputDir(testServices, TranslationMode.PER_MODULE_PROD_MINIMIZED_NAMES), perModuleDceOutputDir)
+        copy(JsEnvironmentConfigurator.getJsArtifactsOutputDir(testServices, TranslationMode.PER_FILE_DEV), perFileOutputDir)
+        copy(JsEnvironmentConfigurator.getJsArtifactsOutputDir(testServices, TranslationMode.PER_FILE_PROD_MINIMIZED_NAMES), perFileDceOutputDir)
         copy(JsEnvironmentConfigurator.getMinificationJsArtifactsOutputDir(testServices), minOutputDir)
     }
 
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/AbstractJsPartialLinkageTestCase.kt b/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/AbstractJsPartialLinkageTestCase.kt
index 0764051ea7a..d1fe65253bd 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/AbstractJsPartialLinkageTestCase.kt
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/AbstractJsPartialLinkageTestCase.kt
@@ -23,11 +23,11 @@ import org.jetbrains.kotlin.config.CompilerConfiguration
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.diagnostics.DiagnosticReporterFactory
 import org.jetbrains.kotlin.ir.backend.js.*
-import org.jetbrains.kotlin.ir.backend.js.codegen.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.ic.CacheUpdater
 import org.jetbrains.kotlin.ir.backend.js.ic.JsExecutableProducer
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.CompilationOutputs
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.IrModuleToJsTransformer
+import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.TranslationMode
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
 import org.jetbrains.kotlin.ir.declarations.impl.IrFactoryImpl
@@ -346,7 +346,7 @@ abstract class AbstractJsPartialLinkageTestCase(val compilerType: CompilerType)
             relativeRequirePath = true
         )
 
-        return jsExecutableProducer.buildExecutable(multiModule = true, outJsProgram = true).compilationOut
+        return jsExecutableProducer.buildExecutable(granularity = JsGenerationGranularity.PER_MODULE, outJsProgram = true).compilationOut
     }
 
     private val IrModuleFragment.exportName get() = "kotlin_${name.asStringStripSpecialMarkers()}"
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/utils/JsIrIncrementalDataProvider.kt b/js/js.tests/test/org/jetbrains/kotlin/js/test/utils/JsIrIncrementalDataProvider.kt
index 48d0e362615..a8a3b48a08f 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/utils/JsIrIncrementalDataProvider.kt
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/utils/JsIrIncrementalDataProvider.kt
@@ -35,7 +35,7 @@ private class TestArtifactCache(val moduleName: String, val binaryAsts: MutableM
                     // TODO: It will be better to use saved fragments, but it doesn't work
                     //  Merger.merge() + JsNode.resolveTemporaryNames() modify fragments,
                     //  therefore the sequential calls produce different results
-                    fragment = deserializeJsIrProgramFragment(it.value)
+                    fragments = deserializeJsIrProgramFragment(it.value)
                 )
             }
         )
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/utils/RunnerUtils.kt b/js/js.tests/test/org/jetbrains/kotlin/js/test/utils/RunnerUtils.kt
index 779eeae405c..9e166590603 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/utils/RunnerUtils.kt
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/utils/RunnerUtils.kt
@@ -50,7 +50,7 @@ private fun extractJsFiles(
     fun copyInputJsFile(module: TestModule, inputJsFile: TestFile): String {
         val newName = module.getNameFor(inputJsFile, testServices)
         val targetFile = File(outputDir, newName)
-        targetFile.writeText(inputJsFile.originalContent)
+        targetFile.writeText(inputJsFile.originalContent.trim())
         return targetFile.absolutePath
     }
 
@@ -68,7 +68,7 @@ private fun extractJsFiles(
     return before to after
 }
 
-fun getAdditionalFilePathes(testServices: TestServices, mode: TranslationMode = TranslationMode.FULL_DEV): List<String> {
+fun getAdditionalFilePaths(testServices: TestServices, mode: TranslationMode = TranslationMode.FULL_DEV): List<String> {
     return getAdditionalFiles(testServices, mode, true).map { it.absolutePath }
 }
 
@@ -100,7 +100,7 @@ fun getAdditionalFiles(
     return additionalFiles
 }
 
-fun getAdditionalMainFilePathes(testServices: TestServices, mode: TranslationMode = TranslationMode.FULL_DEV): List<String> {
+fun getAdditionalMainFilePaths(testServices: TestServices, mode: TranslationMode = TranslationMode.FULL_DEV): List<String> {
     return getAdditionalMainFiles(testServices, mode, shouldCopyFiles = true).map { it.absolutePath }
 }
 
@@ -157,12 +157,13 @@ fun getAllFilesForRunner(
 
             val outputFile = getModeOutputFilePath(testServices, module, mode)
             val (inputJsFilesBefore, inputJsFilesAfter) = extractJsFiles(testServices, testServices.moduleStructure.modules, mode)
-            val additionalFiles = getAdditionalFilePathes(testServices, mode)
-            val additionalMainFiles = getAdditionalMainFilePathes(testServices, mode)
+            val additionalFiles = getAdditionalFilePaths(testServices, mode)
+            val additionalMainFiles = getAdditionalMainFilePaths(testServices, mode)
 
             outputs.dependencies.forEach { (moduleId, _) ->
                 paths += outputFile.augmentWithModuleName(moduleId)
             }
+
             paths += outputFile
 
             result[mode] = additionalFiles + inputJsFilesBefore + paths + commonFiles + additionalMainFiles + inputJsFilesAfter
@@ -171,8 +172,8 @@ fun getAllFilesForRunner(
         return result
     } else {
         val (inputJsFilesBefore, inputJsFilesAfter) = extractJsFiles(testServices, testServices.moduleStructure.modules)
-        val additionalFiles = getAdditionalFilePathes(testServices)
-        val additionalMainFiles = getAdditionalMainFilePathes(testServices)
+        val additionalFiles = getAdditionalFilePaths(testServices)
+        val additionalMainFiles = getAdditionalMainFilePaths(testServices)
         // Old BE
         val outputDir = JsEnvironmentConfigurator.getJsArtifactsOutputDir(testServices)
         val dceOutputDir = JsEnvironmentConfigurator.getJsArtifactsOutputDir(testServices, TranslationMode.FULL_PROD_MINIMIZED_NAMES)
diff --git a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/fir/FirJsBoxTestGenerated.java b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/fir/FirJsBoxTestGenerated.java
index ed6eabf5e62..d06df3336ec 100644
--- a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/fir/FirJsBoxTestGenerated.java
+++ b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/fir/FirJsBoxTestGenerated.java
@@ -2421,6 +2421,12 @@ public class FirJsBoxTestGenerated extends AbstractFirJsBoxTest {
                 runTest("js/js.translator/testData/box/esModules/jsExport/jsExportInClass.kt");
             }
 
+            @Test
+            @TestMetadata("perFileExportedApi.kt")
+            public void testPerFileExportedApi() throws Exception {
+                runTest("js/js.translator/testData/box/esModules/jsExport/perFileExportedApi.kt");
+            }
+
             @Test
             @TestMetadata("recursiveExport.kt")
             public void testRecursiveExport() throws Exception {
diff --git a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsES6TestGenerated.java b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsES6TestGenerated.java
index 77532aee601..dc5fc48e86f 100644
--- a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsES6TestGenerated.java
+++ b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsES6TestGenerated.java
@@ -2527,6 +2527,12 @@ public class IrBoxJsES6TestGenerated extends AbstractIrBoxJsES6Test {
                 runTest("js/js.translator/testData/box/esModules/jsExport/jsExportInClass.kt");
             }
 
+            @Test
+            @TestMetadata("perFileExportedApi.kt")
+            public void testPerFileExportedApi() throws Exception {
+                runTest("js/js.translator/testData/box/esModules/jsExport/perFileExportedApi.kt");
+            }
+
             @Test
             @TestMetadata("recursiveExport.kt")
             public void testRecursiveExport() throws Exception {
diff --git a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsTestGenerated.java b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsTestGenerated.java
index 650b5a1eea8..19a07885c28 100644
--- a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsTestGenerated.java
+++ b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsTestGenerated.java
@@ -2421,6 +2421,12 @@ public class IrBoxJsTestGenerated extends AbstractIrBoxJsTest {
                 runTest("js/js.translator/testData/box/esModules/jsExport/jsExportInClass.kt");
             }
 
+            @Test
+            @TestMetadata("perFileExportedApi.kt")
+            public void testPerFileExportedApi() throws Exception {
+                runTest("js/js.translator/testData/box/esModules/jsExport/perFileExportedApi.kt");
+            }
+
             @Test
             @TestMetadata("recursiveExport.kt")
             public void testRecursiveExport() throws Exception {
diff --git a/js/js.translator/testData/box/esModules/jsExport/perFileExportedApi.kt b/js/js.translator/testData/box/esModules/jsExport/perFileExportedApi.kt
new file mode 100644
index 00000000000..9f8c3bc35d6
--- /dev/null
+++ b/js/js.translator/testData/box/esModules/jsExport/perFileExportedApi.kt
@@ -0,0 +1,39 @@
+// DONT_TARGET_EXACT_BACKEND: JS
+// SKIP_MINIFICATION
+// ES_MODULES
+// SPLIT_PER_FILE
+
+// FILE: base.kt
+
+@JsExport
+open class Base() {
+    var bar = "bar"
+    fun foo() = "foo"
+}
+
+// FILE: a.kt
+
+@JsExport
+class A : Base() {
+    val pong = "pong"
+    fun ping() = "ping"
+}
+
+// FILE: function.kt
+
+@JsExport
+fun create() = A()
+
+// FILE: main.kt
+@JsModule("./perFileExportedApi.mjs")
+external fun jsBox(): String
+
+fun box(): String {
+    val res = jsBox()
+
+    if (res != "bar&not bar&foo&ping&pong") {
+        return "Fail: ${res}"
+    }
+
+    return "OK"
+}
diff --git a/js/js.translator/testData/box/esModules/jsExport/perFileExportedApi.mjs b/js/js.translator/testData/box/esModules/jsExport/perFileExportedApi.mjs
new file mode 100644
index 00000000000..b8fbad10f67
--- /dev/null
+++ b/js/js.translator/testData/box/esModules/jsExport/perFileExportedApi.mjs
@@ -0,0 +1,15 @@
+import { create } from "./perFileExportedApi-kotlin_main_v5/function.export.mjs";
+
+export default function() {
+    let result = ""
+    const a = create()
+
+    result += a.bar
+    a.bar = "not bar"
+    result += `&${a.bar}`
+    result += `&${a.foo()}`
+    result += `&${a.ping()}`
+    result += `&${a.pong}`
+
+    return result
+};
diff --git a/js/js.translator/testData/incremental/invalidation/typeScriptExports/project.info b/js/js.translator/testData/incremental/invalidation/typeScriptExports/project.info
index bd285384327..1355b89bf22 100644
--- a/js/js.translator/testData/incremental/invalidation/typeScriptExports/project.info
+++ b/js/js.translator/testData/incremental/invalidation/typeScriptExports/project.info
@@ -1,8 +1,11 @@
 MODULES: lib1, lib2, main
 
-STEP 0..1:
+STEP 0:
     libs: lib1, lib2, main
     dirty js: lib1, lib2, main
+STEP 1:
+    libs: lib1, lib2, main
+    dirty js: lib1, lib2
 STEP 2:
     libs: lib1, lib2, main
     dirty js: lib1, lib2
@@ -11,7 +14,7 @@ STEP 3:
     dirty js: lib2, main
 STEP 4:
     libs: lib1, lib2, main
-    dirty js: lib1, lib2, main
+    dirty js: lib1, lib2
 STEP 5..6:
     libs: lib1, lib2, main
     dirty js: lib2, main
diff --git a/libraries/stdlib/api/js-v1/kotlin.js.kt b/libraries/stdlib/api/js-v1/kotlin.js.kt
index 88b996fd708..271be73e316 100644
--- a/libraries/stdlib/api/js-v1/kotlin.js.kt
+++ b/libraries/stdlib/api/js-v1/kotlin.js.kt
@@ -210,6 +210,13 @@ public final annotation class ExperimentalJsExport : kotlin.Annotation {
     public constructor ExperimentalJsExport()
 }
 
+@kotlin.RequiresOptIn(level = Level.WARNING)
+@kotlin.annotation.MustBeDocumented
+@kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
+public final annotation class ExperimentalJsFileName : kotlin.Annotation {
+    public constructor ExperimentalJsFileName()
+}
+
 public external object JSON {
     public final fun <T> parse(text: kotlin.String): T
 
@@ -266,6 +273,14 @@ public final annotation class JsExternalInheritorsOnly : kotlin.Annotation {
     public constructor JsExternalInheritorsOnly()
 }
 
+@kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.FILE})
+public final annotation class JsFileName : kotlin.Annotation {
+    public constructor JsFileName(name: kotlin.String)
+
+    public final val name: kotlin.String { get; }
+}
+
 @kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
 @kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS, AnnotationTarget.PROPERTY, AnnotationTarget.FUNCTION, AnnotationTarget.FILE})
 public final annotation class JsModule : kotlin.Annotation {
@@ -275,7 +290,7 @@ public final annotation class JsModule : kotlin.Annotation {
 }
 
 @kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
-@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS, AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY, AnnotationTarget.CONSTRUCTOR, AnnotationTarget.PROPERTY_GETTER, AnnotationTarget.PROPERTY_SETTER})
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.FILE, AnnotationTarget.CLASS, AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY, AnnotationTarget.CONSTRUCTOR, AnnotationTarget.PROPERTY_GETTER, AnnotationTarget.PROPERTY_SETTER})
 public final annotation class JsName : kotlin.Annotation {
     public constructor JsName(name: kotlin.String)
 
diff --git a/libraries/stdlib/api/js/kotlin.js.kt b/libraries/stdlib/api/js/kotlin.js.kt
index 1a7c76a73ee..2e968a7d86e 100644
--- a/libraries/stdlib/api/js/kotlin.js.kt
+++ b/libraries/stdlib/api/js/kotlin.js.kt
@@ -209,6 +209,13 @@ public final annotation class ExperimentalJsExport : kotlin.Annotation {
     public constructor ExperimentalJsExport()
 }
 
+@kotlin.RequiresOptIn(level = Level.WARNING)
+@kotlin.annotation.MustBeDocumented
+@kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
+public final annotation class ExperimentalJsFileName : kotlin.Annotation {
+    public constructor ExperimentalJsFileName()
+}
+
 public external object JSON {
     public final fun <T> parse(text: kotlin.String): T
 
@@ -265,6 +272,14 @@ public final annotation class JsExternalInheritorsOnly : kotlin.Annotation {
     public constructor JsExternalInheritorsOnly()
 }
 
+@kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.FILE})
+public final annotation class JsFileName : kotlin.Annotation {
+    public constructor JsFileName(name: kotlin.String)
+
+    public final val name: kotlin.String { get; }
+}
+
 @kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
 @kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS, AnnotationTarget.PROPERTY, AnnotationTarget.FUNCTION, AnnotationTarget.FILE})
 public final annotation class JsModule : kotlin.Annotation {
@@ -274,7 +289,7 @@ public final annotation class JsModule : kotlin.Annotation {
 }
 
 @kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
-@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS, AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY, AnnotationTarget.CONSTRUCTOR, AnnotationTarget.PROPERTY_GETTER, AnnotationTarget.PROPERTY_SETTER})
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.FILE, AnnotationTarget.CLASS, AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY, AnnotationTarget.CONSTRUCTOR, AnnotationTarget.PROPERTY_GETTER, AnnotationTarget.PROPERTY_SETTER})
 public final annotation class JsName : kotlin.Annotation {
     public constructor JsName(name: kotlin.String)
 
diff --git a/libraries/stdlib/common/src/kotlin/JsAnnotationsH.kt b/libraries/stdlib/common/src/kotlin/JsAnnotationsH.kt
index 6a5aef9d245..56f843a2090 100644
--- a/libraries/stdlib/common/src/kotlin/JsAnnotationsH.kt
+++ b/libraries/stdlib/common/src/kotlin/JsAnnotationsH.kt
@@ -10,10 +10,34 @@ import kotlin.annotation.AnnotationTarget.*
 /**
  * Gives a declaration (a function, a property or a class) specific name in JavaScript.
  */
-@Target(CLASS, FUNCTION, PROPERTY, CONSTRUCTOR, PROPERTY_GETTER, PROPERTY_SETTER)
+@Target(FILE, CLASS, FUNCTION, PROPERTY, CONSTRUCTOR, PROPERTY_GETTER, PROPERTY_SETTER)
 @OptionalExpectation
 public expect annotation class JsName(val name: String)
 
+/**
+ * Marks experimental [JsFileName] annotation.
+ *
+ * Note that behavior of these annotations will likely be changed in the future.
+ *
+ * Usages of such annotations will be reported as warnings unless an explicit opt-in with
+ * the [OptIn] annotation, e.g. `@OptIn(ExperimentalJsFileName::class)`,
+ * or with the `-opt-in=kotlin.js.ExperimentalJsFileName` compiler option is given.
+ */
+@RequiresOptIn(level = RequiresOptIn.Level.WARNING)
+@MustBeDocumented
+@Retention(AnnotationRetention.BINARY)
+public annotation class ExperimentalJsFileName
+
+/**
+ * Specifies the name of the compiled file produced from the annotated source file instead of the default one.
+ *
+ * This annotation can be applied only to files and only when the compilation granularity is `PER_FILE`.
+ */
+@Target(FILE)
+@OptionalExpectation
+@ExperimentalJsFileName
+public expect annotation class JsFileName(val name: String)
+
 /**
  * Marks experimental JS export annotations.
  *
diff --git a/libraries/stdlib/js-ir-minimal-for-test/build.gradle.kts b/libraries/stdlib/js-ir-minimal-for-test/build.gradle.kts
index b7605e8e2d4..e0ed6e532b6 100644
--- a/libraries/stdlib/js-ir-minimal-for-test/build.gradle.kts
+++ b/libraries/stdlib/js-ir-minimal-for-test/build.gradle.kts
@@ -78,7 +78,7 @@ val jsMainSources by task<Sync> {
             listOf(
                 "libraries/stdlib/js/src/org.w3c/**",
                 "libraries/stdlib/js/src/kotlin/char.kt",
-                "libraries/stdlib/js/src/kotlin/collections.kt",
+                "libraries/stdlib/js/src/kotlin/collectionJs.kt",
                 "libraries/stdlib/js/src/kotlin/collections/**",
                 "libraries/stdlib/js/src/kotlin/time/**",
                 "libraries/stdlib/js/src/kotlin/console.kt",
@@ -90,7 +90,7 @@ val jsMainSources by task<Sync> {
                 "libraries/stdlib/js/src/kotlin/json.kt",
                 "libraries/stdlib/js/src/kotlin/promise.kt",
                 "libraries/stdlib/js/src/kotlin/regexp.kt",
-                "libraries/stdlib/js/src/kotlin/sequence.kt",
+                "libraries/stdlib/js/src/kotlin/sequenceJs.kt",
                 "libraries/stdlib/js/src/kotlin/throwableExtensions.kt",
                 "libraries/stdlib/js/src/kotlin/text/**",
                 "libraries/stdlib/js/src/kotlin/reflect/KTypeHelpers.kt",
diff --git a/libraries/stdlib/js-ir/runtime/charSequence.kt b/libraries/stdlib/js-ir/runtime/charSequenceJs.kt
similarity index 100%
rename from libraries/stdlib/js-ir/runtime/charSequence.kt
rename to libraries/stdlib/js-ir/runtime/charSequenceJs.kt
diff --git a/libraries/stdlib/js-ir/runtime/metadataUtils.kt b/libraries/stdlib/js-ir/runtime/metadataUtils.kt
new file mode 100644
index 00000000000..2fb0258362c
--- /dev/null
+++ b/libraries/stdlib/js-ir/runtime/metadataUtils.kt
@@ -0,0 +1,95 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+package kotlin.js
+
+internal fun setMetadataFor(
+    ctor: Ctor,
+    name: String?,
+    metadataConstructor: (name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?) -> Metadata,
+    parent: Ctor?,
+    interfaces: Array<dynamic>?,
+    associatedObjectKey: Number?,
+    associatedObjects: dynamic,
+    suspendArity: Array<Int>?
+) {
+    if (parent != null) {
+        js("""
+          ctor.prototype = Object.create(parent.prototype)
+          ctor.prototype.constructor = ctor;
+        """)
+    }
+
+    val metadata = metadataConstructor(name, associatedObjectKey, associatedObjects, suspendArity ?: js("[]"))
+    ctor.`$metadata$` = metadata
+
+    if (interfaces != null) {
+        val receiver = if (metadata.iid != null) ctor else ctor.prototype
+        receiver.`$imask$` = implement(interfaces)
+    }
+}
+
+// There was a problem with per-module compilation (KT-55758) when the top-level state (iid) was reinitialized during stdlib module initialization
+// As a result we miss already incremented iid and had the same iids in two different modules
+// So, to keep the state consistent it was moved into the variable without initializer and function
+@Suppress("MUST_BE_INITIALIZED")
+private var iid: dynamic
+
+private fun generateInterfaceId(): Int {
+    if (iid === VOID) {
+        iid = 0
+    }
+    iid = iid.unsafeCast<Int>() + 1
+    return iid.unsafeCast<Int>()
+}
+
+
+internal fun interfaceMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
+    return createMetadata("interface", name, associatedObjectKey, associatedObjects, suspendArity, generateInterfaceId())
+}
+
+internal fun objectMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
+    return createMetadata("object", name, associatedObjectKey, associatedObjects, suspendArity, null)
+}
+
+internal fun classMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
+    return createMetadata("class", name, associatedObjectKey, associatedObjects, suspendArity, null)
+}
+
+// Seems like we need to disable this check if variables are used inside js annotation
+@Suppress("UNUSED_PARAMETER", "UNUSED_VARIABLE")
+private fun createMetadata(
+    kind: String,
+    name: String?,
+    associatedObjectKey: Number?,
+    associatedObjects: dynamic,
+    suspendArity: Array<Int>?,
+    iid: Int?
+): Metadata {
+    val undef = VOID
+    return js("""({
+    kind: kind,
+    simpleName: name,
+    associatedObjectKey: associatedObjectKey,
+    associatedObjects: associatedObjects,
+    suspendArity: suspendArity,
+    ${'$'}kClass$: undef,
+    iid: iid
+})""")
+}
+
+internal external interface Metadata {
+    val kind: String
+    // This field gives fast access to the prototype of metadata owner (Object.getPrototypeOf())
+    // Can be pre-initialized or lazy initialized and then should be immutable
+    val simpleName: String?
+    val associatedObjectKey: Number?
+    val associatedObjects: dynamic
+    val suspendArity: Array<Int>?
+    val iid: Int?
+
+    var `$kClass$`: dynamic
+
+    var errorInfo: Int? // Bits set for overridden properties: "message" => 0x1, "cause" => 0x2
+}
\ No newline at end of file
diff --git a/libraries/stdlib/js-ir/runtime/typeCheckUtils.kt b/libraries/stdlib/js-ir/runtime/typeCheckUtils.kt
index 970d96d8000..918d873da21 100644
--- a/libraries/stdlib/js-ir/runtime/typeCheckUtils.kt
+++ b/libraries/stdlib/js-ir/runtime/typeCheckUtils.kt
@@ -5,95 +5,6 @@
 
 package kotlin.js
 
-internal fun setMetadataFor(
-    ctor: Ctor,
-    name: String?,
-    metadataConstructor: (name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?) -> Metadata,
-    parent: Ctor?,
-    interfaces: Array<dynamic>?,
-    associatedObjectKey: Number?,
-    associatedObjects: dynamic,
-    suspendArity: Array<Int>?
-) {
-    if (parent != null) {
-        js("""
-          ctor.prototype = Object.create(parent.prototype)
-          ctor.prototype.constructor = ctor;
-        """)
-    }
-
-    val metadata = metadataConstructor(name, associatedObjectKey, associatedObjects, suspendArity ?: js("[]"))
-    ctor.`$metadata$` = metadata
-
-    if (interfaces != null) {
-        val receiver = if (metadata.iid != null) ctor else ctor.prototype
-        receiver.`$imask$` = implement(interfaces)
-    }
-}
-
-// There was a problem with per-module compilation (KT-55758) when the top-level state (iid) was reinitialized during stdlib module initialization
-// As a result we miss already incremented iid and had the same iids in two different modules
-// So, to keep the state consistent it was moved into the next lateinit variable and function
-private lateinit var iid: Any
-
-private fun generateInterfaceId(): Int {
-    if (!::iid.isInitialized) {
-        iid = 0
-    }
-    iid = iid.unsafeCast<Int>() + 1
-    return iid.unsafeCast<Int>()
-}
-
-
-internal fun interfaceMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
-    return createMetadata("interface", name, associatedObjectKey, associatedObjects, suspendArity, generateInterfaceId())
-}
-
-internal fun objectMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
-    return createMetadata("object", name, associatedObjectKey, associatedObjects, suspendArity, null)
-}
-
-internal fun classMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
-    return createMetadata("class", name, associatedObjectKey, associatedObjects, suspendArity, null)
-}
-
-// Seems like we need to disable this check if variables are used inside js annotation
-@Suppress("UNUSED_PARAMETER", "UNUSED_VARIABLE")
-private fun createMetadata(
-    kind: String,
-    name: String?,
-    associatedObjectKey: Number?,
-    associatedObjects: dynamic,
-    suspendArity: Array<Int>?,
-    iid: Int?
-): Metadata {
-    val undef = VOID
-    return js("""({
-    kind: kind,
-    simpleName: name,
-    associatedObjectKey: associatedObjectKey,
-    associatedObjects: associatedObjects,
-    suspendArity: suspendArity,
-    ${'$'}kClass$: undef,
-    iid: iid
-})""")
-}
-
-internal external interface Metadata {
-    val kind: String
-    // This field gives fast access to the prototype of metadata owner (Object.getPrototypeOf())
-    // Can be pre-initialized or lazy initialized and then should be immutable
-    val simpleName: String?
-    val associatedObjectKey: Number?
-    val associatedObjects: dynamic
-    val suspendArity: Array<Int>?
-    val iid: Int?
-
-    var `$kClass$`: dynamic
-
-    var errorInfo: Int? // Bits set for overridden properties: "message" => 0x1, "cause" => 0x2
-}
-
 internal external interface Ctor {
     var `$imask$`: BitMask?
     var `$metadata$`: Metadata
@@ -128,22 +39,6 @@ internal fun calculateErrorInfo(proto: dynamic): Int {
 
 private fun getPrototypeOf(obj: dynamic) = JsObject.getPrototypeOf(obj)
 
-private fun searchForMetadata(obj: dynamic): Metadata? {
-    if (obj == null) {
-        return null
-    }
-    var metadata: Metadata? = obj.`$metadata$`
-    var currentObject = getPrototypeOf(obj)
-
-    while (metadata == null && currentObject != null) {
-        val currentConstructor = currentObject.constructor
-        metadata = currentConstructor.`$metadata$`
-        currentObject = getPrototypeOf(currentObject)
-    }
-
-    return metadata
-}
-
 private fun isInterfaceImpl(obj: dynamic, iface: Int): Boolean {
     val mask: BitMask = obj.`$imask$`.unsafeCast<BitMask?>() ?: return false
     return mask.isBitSet(iface)
diff --git a/libraries/stdlib/js-v1/runtime/hacks.kt b/libraries/stdlib/js-v1/runtime/hacks.kt
index 7d5d391ca65..121b8619414 100644
--- a/libraries/stdlib/js-v1/runtime/hacks.kt
+++ b/libraries/stdlib/js-v1/runtime/hacks.kt
@@ -8,7 +8,7 @@ package kotlin.js
 import kotlin.annotation.AnnotationTarget.*
 
 @Retention(AnnotationRetention.BINARY)
-@Target(CLASS, FUNCTION, PROPERTY, CONSTRUCTOR, PROPERTY_GETTER, PROPERTY_SETTER)
+@Target(FILE, CLASS, FUNCTION, PROPERTY, CONSTRUCTOR, PROPERTY_GETTER, PROPERTY_SETTER)
 internal external annotation class JsName(val name: String)
 
 internal external annotation class native
diff --git a/libraries/stdlib/js/src/kotlin/annotations.kt b/libraries/stdlib/js/src/kotlin/annotations.kt
index a613d6e1e93..eb744371dc2 100644
--- a/libraries/stdlib/js/src/kotlin/annotations.kt
+++ b/libraries/stdlib/js/src/kotlin/annotations.kt
@@ -58,9 +58,18 @@ internal annotation class marker
  *
  */
 @Retention(AnnotationRetention.BINARY)
-@Target(CLASS, FUNCTION, PROPERTY, CONSTRUCTOR, PROPERTY_GETTER, PROPERTY_SETTER)
+@Target(FILE, CLASS, FUNCTION, PROPERTY, CONSTRUCTOR, PROPERTY_GETTER, PROPERTY_SETTER)
 public actual annotation class JsName(actual val name: String)
 
+/**
+ * Specifies the name of the compiled file produced from the annotated source file instead of the default one.
+ *
+ * This annotation can be applied only to files and only when the compilation granularity is `PER_FILE`.
+ */
+@Retention(AnnotationRetention.BINARY)
+@Target(FILE)
+public actual annotation class JsFileName(actual val name: String)
+
 /**
  * Denotes an `external` declaration that must be imported from native JavaScript library.
  *
diff --git a/libraries/stdlib/js/src/kotlin/collections.kt b/libraries/stdlib/js/src/kotlin/collectionJs.kt
similarity index 100%
rename from libraries/stdlib/js/src/kotlin/collections.kt
rename to libraries/stdlib/js/src/kotlin/collectionJs.kt
diff --git a/libraries/stdlib/js/src/kotlin/sequence.kt b/libraries/stdlib/js/src/kotlin/sequenceJs.kt
similarity index 100%
rename from libraries/stdlib/js/src/kotlin/sequence.kt
rename to libraries/stdlib/js/src/kotlin/sequenceJs.kt
diff --git a/libraries/stdlib/js/src/kotlin/text/char.kt b/libraries/stdlib/js/src/kotlin/text/charJs.kt
similarity index 100%
rename from libraries/stdlib/js/src/kotlin/text/char.kt
rename to libraries/stdlib/js/src/kotlin/text/charJs.kt
diff --git a/libraries/stdlib/js/src/kotlin/text/string.kt b/libraries/stdlib/js/src/kotlin/text/stringJs.kt
similarity index 100%
rename from libraries/stdlib/js/src/kotlin/text/string.kt
rename to libraries/stdlib/js/src/kotlin/text/stringJs.kt
diff --git a/libraries/stdlib/src/kotlin/collections/Collections.kt b/libraries/stdlib/src/kotlin/collections/Collections.kt
index f49586206b2..feba9cd7b50 100644
--- a/libraries/stdlib/src/kotlin/collections/Collections.kt
+++ b/libraries/stdlib/src/kotlin/collections/Collections.kt
@@ -3,6 +3,9 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
+// TODO: Suppress will be until the next bootstrapping, after the bootstrapping the annotation should be replaced with [kotlin.js.JsFileName]
+@file:Suppress("ANNOTATION_IS_NOT_APPLICABLE_TO_MULTIFILE_CLASSES")
+@file:kotlin.js.JsName("CollectionsKt")
 @file:kotlin.jvm.JvmMultifileClass
 @file:kotlin.jvm.JvmName("CollectionsKt")
 @file:OptIn(kotlin.experimental.ExperimentalTypeInference::class)
diff --git a/libraries/stdlib/wasm/src/kotlin/js/annotations.kt b/libraries/stdlib/wasm/src/kotlin/js/annotations.kt
index 0905b5e76d3..82c16f3e71c 100644
--- a/libraries/stdlib/wasm/src/kotlin/js/annotations.kt
+++ b/libraries/stdlib/wasm/src/kotlin/js/annotations.kt
@@ -30,6 +30,7 @@ public actual annotation class JsExport {
  */
 @Retention(AnnotationRetention.BINARY)
 @Target(
+    AnnotationTarget.FILE,
     AnnotationTarget.CLASS,
     AnnotationTarget.FUNCTION,
     AnnotationTarget.PROPERTY,
diff --git a/libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-stdlib-runtime-merged.txt b/libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-stdlib-runtime-merged.txt
index b0e9ca7245d..9eee8ad04fb 100644
--- a/libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-stdlib-runtime-merged.txt
+++ b/libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-stdlib-runtime-merged.txt
@@ -3384,6 +3384,9 @@ public final class kotlin/jdk7/AutoCloseableKt {
 public abstract interface annotation class kotlin/js/ExperimentalJsExport : java/lang/annotation/Annotation {
 }
 
+public abstract interface annotation class kotlin/js/ExperimentalJsFileName : java/lang/annotation/Annotation {
+}
+
 public final class kotlin/jvm/JvmClassMappingKt {
 	public static final fun getAnnotationClass (Ljava/lang/annotation/Annotation;)Lkotlin/reflect/KClass;
 	public static final fun getJavaClass (Ljava/lang/Object;)Ljava/lang/Class;