Revert "Revert [JS IR] commits that failed build"

This reverts commit 740f851a

build.gradle.kts

@@ -8,7 +8,7 @@ buildscript {
     extra["defaultSnapshotVersion"] = "1.3-SNAPSHOT"
     val cacheRedirectorEnabled = findProperty("cacheRedirectorEnabled")?.toString()?.toBoolean() == true
 
-    kotlinBootstrapFrom(BootstrapOption.BintrayBootstrap("1.3.70-dev-1070", cacheRedirectorEnabled))
+    kotlinBootstrapFrom(BootstrapOption.BintrayBootstrap("1.3.70-dev-1140", cacheRedirectorEnabled))
 
     repositories {
         bootstrapKotlinRepo?.let(::maven)

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JSCompilerArguments.kt

@@ -106,22 +106,24 @@ class K2JSCompilerArguments : CommonCompilerArguments() {
 
     // Advanced options
 
-
+    @Argument(
-    @Argument(value = "-Xir", description = "Use IR backend")
+        value = "-Xir-produce-klib-dir",
-    var irBackend: Boolean by FreezableVar(false)
+        description = "Generate unpacked KLIB into parent directory of output JS file.\n" +
+                "In combination with -meta-info generates both IR and pre-IR versions of library."
+    )
+    var irProduceKlibDir: Boolean by FreezableVar(false)
 
     @Argument(
-        value = "-Xir-produce-only",
+        value = "-Xir-produce-klib-file",
-        valueDescription = "{ klib, js }",
+        description = "Generate packed klib into file specified by -output. Disables pre-IR backend"
-        description = "Type of output to produce. Overrides -meta-info argument."
     )
-    var irProduceOnly: String? by NullableStringFreezableVar(null)
+    var irProduceKlibFile: Boolean by FreezableVar(false)
 
-    @Argument(
+    @Argument(value = "-Xir-produce-js", description = "Generates JS file using IR backend. Also disables pre-IR backend")
-        value = "-Xir-legacy-gradle-plugin-compatibility",
+    var irProduceJs: Boolean by FreezableVar(false)
-        description = "Make KLIB generation compatible with legacy gradle plugin"
+
-    )
+    @Argument(value = "-Xir-only", description = "Disables pre-IR backend")
-    var irLegacyGradlePluginCompatibility: Boolean by FreezableVar(false)
+    var irOnly: Boolean by FreezableVar(false)
 
     @GradleOption(DefaultValues.BooleanTrueDefault::class)
     @Argument(value = "-Xtyped-arrays", description = "Translate primitive arrays to JS typed arrays")
@@ -144,3 +146,9 @@ class K2JSCompilerArguments : CommonCompilerArguments() {
     @Argument(value = "-Xenable-js-scripting", description = "Enable experimental support of .kts files using K/JS (with -Xir only)")
     var enableJsScripting: Boolean by FreezableVar(false)
 }
+
+fun K2JSCompilerArguments.isPreIrBackendDisabled(): Boolean =
+    irOnly || irProduceJs || irProduceKlibFile
+
+fun K2JSCompilerArguments.isIrBackendEnabled(): Boolean =
+    irProduceKlibDir || irProduceJs || irProduceKlibFile

compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JSCompiler.java

@@ -36,6 +36,7 @@ import org.jetbrains.kotlin.cli.common.CLIConfigurationKeys;
 import org.jetbrains.kotlin.cli.common.CommonCompilerPerformanceManager;
 import org.jetbrains.kotlin.cli.common.ExitCode;
 import org.jetbrains.kotlin.cli.common.arguments.K2JSCompilerArguments;
+import org.jetbrains.kotlin.cli.common.arguments.K2JSCompilerArgumentsKt;
 import org.jetbrains.kotlin.cli.common.arguments.K2JsArgumentConstants;
 import org.jetbrains.kotlin.cli.common.config.ContentRootsKt;
 import org.jetbrains.kotlin.cli.common.messages.AnalyzerWithCompilerReport;
@@ -45,7 +46,6 @@ import org.jetbrains.kotlin.cli.common.messages.MessageUtil;
 import org.jetbrains.kotlin.cli.common.output.OutputUtilsKt;
 import org.jetbrains.kotlin.cli.jvm.compiler.EnvironmentConfigFiles;
 import org.jetbrains.kotlin.cli.jvm.compiler.KotlinCoreEnvironment;
-import org.jetbrains.kotlin.cli.jvm.plugins.PluginCliParser;
 import org.jetbrains.kotlin.config.*;
 import org.jetbrains.kotlin.incremental.components.ExpectActualTracker;
 import org.jetbrains.kotlin.incremental.components.LookupTracker;
@@ -186,8 +186,13 @@ public class K2JSCompiler extends CLICompiler<K2JSCompilerArguments> {
     ) {
         MessageCollector messageCollector = configuration.getNotNull(CLIConfigurationKeys.MESSAGE_COLLECTOR_KEY);
 
-        if (arguments.getIrBackend()) {
+        ExitCode exitCode = OK;
-            return getIrCompiler().doExecute(arguments, configuration, rootDisposable, paths);
+
+        if (K2JSCompilerArgumentsKt.isIrBackendEnabled(arguments)) {
+            exitCode = getIrCompiler().doExecute(arguments, configuration.copy(), rootDisposable, paths);
+        }
+        if (K2JSCompilerArgumentsKt.isPreIrBackendDisabled(arguments)) {
+            return exitCode;
         }
 
         if (arguments.getFreeArgs().isEmpty() && !IncrementalCompilation.isEnabledForJs()) {
@@ -388,8 +393,10 @@ public class K2JSCompiler extends CLICompiler<K2JSCompilerArguments> {
             @NotNull CompilerConfiguration configuration, @NotNull K2JSCompilerArguments arguments,
             @NotNull Services services
     ) {
-        if (arguments.getIrBackend()) {
+        if (K2JSCompilerArgumentsKt.isIrBackendEnabled(arguments)) {
             getIrCompiler().setupPlatformSpecificArgumentsAndServices(configuration, arguments, services);
+        }
+        if (K2JSCompilerArgumentsKt.isPreIrBackendDisabled(arguments)) {
             return;
         }
 

compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt

@@ -9,7 +9,8 @@ import com.intellij.openapi.Disposable
 import com.intellij.openapi.util.io.FileUtil
 import com.intellij.openapi.util.text.StringUtil
 import org.jetbrains.kotlin.cli.common.*
-import org.jetbrains.kotlin.cli.common.ExitCode.*
+import org.jetbrains.kotlin.cli.common.ExitCode.COMPILATION_ERROR
+import org.jetbrains.kotlin.cli.common.ExitCode.OK
 import org.jetbrains.kotlin.cli.common.arguments.K2JSCompilerArguments
 import org.jetbrains.kotlin.cli.common.arguments.K2JsArgumentConstants
 import org.jetbrains.kotlin.cli.common.config.addKotlinSourceRoot
@@ -175,17 +176,12 @@ class K2JsIrCompiler : CLICompiler<K2JSCompilerArguments>() {
             it.libraryFile.absolutePath in friendAbsolutePaths
         }
 
-        val produceKind = produceMap[arguments.irProduceOnly]
+        if (arguments.irProduceKlibDir || arguments.irProduceKlibFile) {
-        if (produceKind == null) {
-            messageCollector.report(ERROR, "Unknown produce kind: ${arguments.irProduceOnly}. Valid values are: js, klib")
-        }
-
-        if (produceKind == ProduceKind.KLIB || (produceKind == ProduceKind.DEFAULT && arguments.metaInfo)) {
             val outputKlibPath =
-                if (arguments.irLegacyGradlePluginCompatibility)
+                if (arguments.irProduceKlibDir)
                     File(outputFilePath).parent
                 else
-                    "$outputFilePath.klib"
+                    outputFilePath
 
             generateKLib(
                 project = config.project,
@@ -194,11 +190,11 @@ class K2JsIrCompiler : CLICompiler<K2JSCompilerArguments>() {
                 allDependencies = resolvedLibraries,
                 friendDependencies = friendDependencies,
                 outputKlibPath = outputKlibPath,
-                nopack = arguments.irLegacyGradlePluginCompatibility
+                nopack = arguments.irProduceKlibDir
             )
         }
 
-        if (produceKind == ProduceKind.JS || produceKind == ProduceKind.DEFAULT) {
+        if (arguments.irProduceJs) {
             val phaseConfig = createPhaseConfig(jsPhases, arguments, messageCollector)
 
             val compiledModule = compile(

compiler/incremental-compilation-impl/test/org/jetbrains/kotlin/incremental/AbstractIncrementalJsKlibCompilerRunnerTest.kt

@@ -10,10 +10,8 @@ abstract class AbstractIncrementalJsKlibCompilerRunnerTest : AbstractIncremental
             libraries = "build/js-ir-runtime/full-runtime.klib"
             outputFile = File(destinationDir, "${testDir.name}.klib").path
             sourceMap = true
-            irBackend = true
-            irProduceOnly = "klib"
             // Don't zip klib content since date on files affect the md5 checksum we compute to check whether output files identical
-            irLegacyGradlePluginCompatibility = true
+            irProduceKlibDir = true
         }
 
     override val buildLogFinder: BuildLogFinder

compiler/testData/cli/js/jsExtraHelp.out

@@ -3,10 +3,11 @@ where advanced options include:
   -Xenable-js-scripting      Enable experimental support of .kts files using K/JS (with -Xir only)
   -Xfriend-modules=<path>    Paths to friend modules
   -Xfriend-modules-disabled  Disable internal declaration export
-  -Xir                       Use IR backend
+  -Xir-only                  Disables pre-IR backend
-  -Xir-legacy-gradle-plugin-compatibility
+  -Xir-produce-js            Generates JS file using IR backend. Also disables pre-IR backend
-                             Make KLIB generation compatible with legacy gradle plugin
+  -Xir-produce-klib-dir      Generate unpacked KLIB into parent directory of output JS file.
-  -Xir-produce-only={ klib, js } Type of output to produce. Overrides -meta-info argument.
+                             In combination with -meta-info generates both IR and pre-IR versions of library.
+  -Xir-produce-klib-file     Generate packed klib into file specified by -output. Disables pre-IR backend
   -Xmetadata-only            Generate *.meta.js and *.kjsm files only
   -Xtyped-arrays             Translate primitive arrays to JS typed arrays
   -Xallow-kotlin-package     Allow compiling code in package 'kotlin' and allow not requiring kotlin.stdlib in module-info

libraries/kotlin.test/js-ir/build.gradle

@@ -1,70 +0,0 @@
-description = 'Kotlin Test for JS IR'
-
-apply plugin: 'kotlin-platform-js'
-
-
-dependencies {
-    expectedBy project(':kotlin-test:kotlin-test-common')
-    expectedBy project(':kotlin-test:kotlin-test-annotations-common')
-    compile project(':kotlin-stdlib-js-ir')
-}
-
-def jsCommonDir = "${buildDir}/common-js-sources"
-
-task prepareCommonJsSources(type: Sync) {
-    from "${projectDir}/../js/src/"
-    into jsCommonDir
-}
-
-compileKotlin2Js {
-    dependsOn prepareCommonJsSources
-
-    kotlinOptions {
-        moduleKind = "umd"
-        freeCompilerArgs = [
-                "-Xir",
-                "-Xir-produce-only=klib",
-                "-Xallow-kotlin-package",
-                "-Xuse-experimental=kotlin.contracts.ExperimentalContracts",
-        ]
-    }
-}
-
-sourceSets {
-    main {
-        kotlin {
-            srcDir jsCommonDir
-        }
-    }
-}
-
-compileTestKotlin2Js {
-    kotlinOptions.freeCompilerArgs = [
-        "-Xir",
-        "-Xir-produce-only=js",
-        "-Xallow-kotlin-package",
-    ]
-    kotlinOptions {
-        metaInfo = false
-        moduleKind = "umd"
-    }
-}
-
-task sourcesJar(type: Jar, dependsOn: classes) {
-    classifier = 'sources'
-    from(sourceSets.main.allSource)
-}
-
-archivesBaseName = 'kotlin-test-js-ir'
-
-jar {
-    manifestAttributes(manifest, project, 'Test')
-}
-
-artifacts {
-    archives sourcesJar
-}
-
-if (project.findProperty("kotlin.stdlib.js.ir.publish")?.toBoolean() == true) {
-    configurePublishing(project)
-}

libraries/kotlin.test/js/build.gradle

@@ -16,7 +16,11 @@ dependencies {
 }
 
 compileKotlin2Js {
-    kotlinOptions.freeCompilerArgs = ["-Xallow-kotlin-package", "-Xuse-experimental=kotlin.contracts.ExperimentalContracts"]
+    kotlinOptions.freeCompilerArgs = [
+            "-Xallow-kotlin-package",
+            "-Xuse-experimental=kotlin.contracts.ExperimentalContracts",
+            "-Xir-produce-klib-dir"
+    ]
     kotlinOptions {
         moduleKind = "umd"
         outputFile = "${buildDir}/classes/main/kotlin-test.js"

libraries/stdlib/js-ir/build.gradle

@@ -92,7 +92,7 @@ configurations {
 dependencies {
     expectedBy project(":kotlin-stdlib-common")
     commonSources project(path: ":kotlin-stdlib-common", configuration: "sources")
-    testCompile project(':kotlin-test:kotlin-test-js-ir')
+    testCompile project(':kotlin-test:kotlin-test-js')
 }
 
 
@@ -107,8 +107,8 @@ compileKotlin2Js {
         main = "noCall"
         verbose = true
         freeCompilerArgs += [
-            "-Xir",
+            "-Xir-produce-klib-dir",
-            "-Xir-produce-only=klib",
+            "-Xir-only",
             "-Xallow-kotlin-package",
             "-Xallow-result-return-type",
             "-Xuse-experimental=kotlin.Experimental",
@@ -120,7 +120,7 @@ compileKotlin2Js {
 }
 
 def testOutputFile = "${buildDir}/classes/kotlin/test/kotlin-stdlib-js-ir_test.js"
-def kotlinTestTestOutputFile = "${project(':kotlin-test:kotlin-test-js-ir').buildDir}/classes/kotlin/test/kotlin-test-js-ir_test.js"
+def kotlinTestTestOutputFile = "${project(':kotlin-test:kotlin-test-js').buildDir}/classes/kotlin/test/kotlin-test-js-ir_test.js"
 
 compileTestKotlin2Js {
     kotlinOptions {
@@ -128,8 +128,7 @@ compileTestKotlin2Js {
         verbose = true
         outputFile = testOutputFile
         freeCompilerArgs += [
-          "-Xir",
+          "-Xir-produce-js",
-          "-Xir-produce-only=js",
           "-verbose",
           "-Xuse-experimental=kotlin.Experimental",
           "-Xuse-experimental=kotlin.ExperimentalUnsignedTypes",
@@ -155,11 +154,6 @@ artifacts {
     archives sourcesJar
 }
 
-
-if (project.findProperty("kotlin.stdlib.js.ir.publish")?.toBoolean() == true) {
-    configurePublishing(project)
-}
-
 node {
     download = true
     version = '8.9.4' // The default 6.9.1 has buggy hyperbolic functions implementation
@@ -177,7 +171,7 @@ task installTeamcityReporter(type: NpmTask) {
 task runMocha(type: NodeTask) {
     dependsOn compileTestKotlin2Js
     dependsOn installMocha
-    dependsOn ':kotlin-test:kotlin-test-js-ir:testClasses'
+    dependsOn ':kotlin-test:kotlin-test-js:testClasses'
 
     script = file("${buildDir}/node_modules/mocha/bin/mocha")
 

libraries/stdlib/js-v1/build.gradle

@@ -14,6 +14,7 @@ configurations {
     commonSources
     distSources
     distJs
+    distLibrary
 }
 
 def builtinsSrcDir = "${buildDir}/builtin-sources"
@@ -283,9 +284,10 @@ jar {
     enabled false
 }
 
-task mergedJar(type: Jar, dependsOn: compileJs) {
+task libraryJarWithoutIr(type: Jar, dependsOn: compileJs) {
     classifier = null
     manifestAttributes(manifest, project, 'Main')
+    destinationDirectory = file("$buildDir/lib/dist")
 
     // TODO: Use standard implementation title after js stdlib detector becomes more flexible (KT-17655)
     Properties properties = new Properties()
@@ -307,6 +309,22 @@ task mergedJar(type: Jar, dependsOn: compileJs) {
     exclude "${experimentalJsModuleName}.*"
 }
 
+task libraryJarWithIr(type: Zip, dependsOn: libraryJarWithoutIr) {
+    def irStdlibJar = tasks.getByPath(":kotlin-stdlib-js-ir:jar")
+    dependsOn(irStdlibJar)
+
+    archiveExtension = "jar"
+    destinationDirectory = file("$buildDir/libs")
+
+    duplicatesStrategy DuplicatesStrategy.FAIL
+
+    from zipTree(libraryJarWithoutIr.archiveFile)
+    from(zipTree(irStdlibJar.archiveFile)) {
+        exclude 'META-INF/*'
+    }
+}
+
+
 task sourcesJar(type: Jar, dependsOn: compileJs) {
     classifier = 'sources'
     includeEmptyDirs false
@@ -352,11 +370,12 @@ task distSourcesJar(type: Jar) {
 
 
 artifacts {
-    runtime mergedJar
+    runtime libraryJarWithIr
-    archives mergedJar
+    archives libraryJarWithIr
     archives sourcesJar
     sources sourcesJar
     distSources distSourcesJar
+    distLibrary libraryJarWithoutIr
 
     compileJs.outputs.files.forEach { artifact ->
         distJs(artifact) { builtBy(compileJs) }

libraries/tools/kotlin-gradle-plugin-integration-tests/build.gradle.kts

@@ -105,8 +105,10 @@ tasks.withType<Test> {
         ":kotlin-reflect:install",
         ":kotlin-annotation-processing-gradle:install",
         ":kotlin-test:kotlin-test-jvm:install",
+        ":kotlin-test:kotlin-test-js:install",
         ":kotlin-gradle-subplugin-example:install",
         ":kotlin-stdlib-jdk8:install",
+        ":kotlin-stdlib-js:install",
         ":examples:annotation-processor-example:install",
         ":kotlin-scripting-common:install",
         ":kotlin-scripting-jvm:install",

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/BaseGradleIT.kt

@@ -198,6 +198,7 @@ abstract class BaseGradleIT {
         val daemonOptionSupported: Boolean = true,
         val incremental: Boolean? = null,
         val incrementalJs: Boolean? = null,
+        val jsIrBackend: Boolean? = null,
         val androidHome: File? = null,
         val javaHome: File? = null,
         val androidGradlePluginVersion: AGPVersion? = null,
@@ -719,6 +720,7 @@ Finished executing task ':$taskName'|
                 add("-Pkotlin.incremental=$it")
             }
             options.incrementalJs?.let { add("-Pkotlin.incremental.js=$it") }
+            options.jsIrBackend?.let { add("-Pkotlin.js.useIrBackend=$it") }
             options.usePreciseJavaTracking?.let { add("-Pkotlin.incremental.usePreciseJavaTracking=$it") }
             options.androidGradlePluginVersion?.let { add("-Pandroid_tools_version=$it") }
             if (options.debug) {

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kotlin2JsGradlePluginIT.kt

@@ -2,169 +2,20 @@ package org.jetbrains.kotlin.gradle
 
 import org.gradle.api.logging.LogLevel
 import org.jetbrains.kotlin.gradle.tasks.USING_JS_INCREMENTAL_COMPILATION_MESSAGE
+import org.jetbrains.kotlin.gradle.tasks.USING_JS_IR_BACKEND_MESSAGE
 import org.jetbrains.kotlin.gradle.util.getFileByName
 import org.jetbrains.kotlin.gradle.util.getFilesByNames
 import org.jetbrains.kotlin.gradle.util.modify
+import org.junit.Assume.assumeFalse
 import org.junit.Test
 import java.io.File
 import java.util.zip.ZipFile
 import kotlin.test.assertEquals
 import kotlin.test.assertTrue
 
-class Kotlin2JsGradlePluginIT : BaseGradleIT() {
+class Kotlin2JsIrGradlePluginIT : AbstractKotlin2JsGradlePluginIT(true)
-    @Test
-    fun testBuildAndClean() {
-        val project = Project("kotlin2JsProject")
-
-        project.build("build") {
-            assertSuccessful()
-            assertReportExists()
-
-            assertTasksExecuted(
-                ":libraryProject:jarSources",
-                ":mainProject:compileKotlin2Js",
-                ":libraryProject:compileKotlin2Js"
-            )
-
-            listOf(
-                "mainProject/web/js/app.js",
-                "mainProject/web/js/lib/kotlin.js",
-                "libraryProject/build/kotlin2js/main/test-library.js",
-                "mainProject/web/js/app.js.map"
-            ).forEach { assertFileExists(it) }
-        }
-
-        project.build("build") {
-            assertSuccessful()
-            assertTasksUpToDate(":mainProject:compileKotlin2Js")
-            assertContainsRegex(":libraryProject:compileTestKotlin2Js (UP-TO-DATE|NO-SOURCE)".toRegex())
-        }
-
-        project.build("clean") {
-            assertSuccessful()
-            assertReportExists()
-
-            // Test that we don't accidentally remove the containing directory
-            // This would fail if we used the default clean task of the copy task
-            assertFileExists("mainProject/web/js/lib")
-
-            assertNoSuchFile("main/project/web/js/app.js.map")
-            assertNoSuchFile("main/project/web/js/example/main.kt")
-        }
-
-        project.build("clean") {
-            assertSuccessful()
-            assertReportExists()
-        }
-    }
-
-    @Test
-    fun testJarIncludesJsDefaultOutput() {
-        val project = Project("kotlin2JsNoOutputFileProject")
-
-        project.build("jar") {
-            assertSuccessful()
-
-            assertTasksExecuted(":compileKotlin2Js")
-            val jarPath = "build/libs/kotlin2JsNoOutputFileProject.jar"
-            assertFileExists(jarPath)
-            val jar = ZipFile(fileInWorkingDir(jarPath))
-            assertEquals(
-                1, jar.entries().asSequence().count { it.name == "kotlin2JsNoOutputFileProject.js" },
-                "The jar should contain an entry `kotlin2JsNoOutputFileProject.js` with no duplicates"
-            )
-        }
-    }
-
-    @Test
-    fun testJarIncludesJsOutputSetExplicitly() {
-        val project = Project("kotlin2JsModuleKind")
-
-        project.build(":jar") {
-            assertSuccessful()
-
-            assertTasksExecuted(":compileKotlin2Js")
-            val jarPath = "build/libs/kotlin2JsModuleKind.jar"
-            assertFileExists(jarPath)
-            val jar = ZipFile(fileInWorkingDir(jarPath))
-            assertEquals(
-                1, jar.entries().asSequence().count { it.name == "app.js" },
-                "The jar should contain an entry `app.js` with no duplicates"
-            )
-        }
-    }
-
-    @Test
-    fun testModuleKind() {
-        val project = Project("kotlin2JsModuleKind")
-
-        project.build("runRhino") {
-            assertSuccessful()
-        }
-    }
-
-    @Test
-    fun testDefaultOutputFile() {
-        val project = Project("kotlin2JsNoOutputFileProject")
-
-        project.build("build") {
-            assertSuccessful()
-            assertFileExists(kotlinClassesDir() + "kotlin2JsNoOutputFileProject.js")
-            assertFileExists(kotlinClassesDir(sourceSet = "test") + "kotlin2JsNoOutputFileProject_test.js")
-        }
-    }
-
-    @Test
-    fun testCompileTestCouldAccessProduction() {
-        val project = Project("kotlin2JsProjectWithTests")
-
-        project.build("build") {
-            assertSuccessful()
-
-            assertTasksExecuted(
-                ":compileKotlin2Js",
-                ":compileTestKotlin2Js"
-            )
-
-            assertFileExists("build/kotlin2js/main/module.js")
-            assertFileExists("build/kotlin2js/test/module-tests.js")
-        }
-    }
-
-    @Test
-    fun testCompilerTestAccessInternalProduction() {
-        val project = Project("kotlin2JsInternalTest")
-
-        project.build("runRhino") {
-            assertSuccessful()
-        }
-    }
-
-    @Test
-    fun testJsCustomSourceSet() {
-        val project = Project("kotlin2JsProjectWithCustomSourceset")
-
-        project.build("build") {
-            assertSuccessful()
-
-            assertTasksExecuted(
-                ":compileKotlin2Js",
-                ":compileIntegrationTestKotlin2Js"
-            )
-
-            assertFileExists("build/kotlin2js/main/module.js")
-            assertFileExists("build/kotlin2js/integrationTest/module-inttests.js")
-
-            val jarPath = "build/libs/kotlin2JsProjectWithCustomSourceset-inttests.jar"
-            assertFileExists(jarPath)
-            val jar = ZipFile(fileInWorkingDir(jarPath))
-            assertEquals(
-                1, jar.entries().asSequence().count { it.name == "module-inttests.js" },
-                "The jar should contain an entry `module-inttests.js` with no duplicates"
-            )
-        }
-    }
 
+class Kotlin2JsGradlePluginIT : AbstractKotlin2JsGradlePluginIT(false) {
     @Test
     fun testKotlinJsBuiltins() {
         val project = Project("kotlinBuiltins")
@@ -180,49 +31,6 @@ class Kotlin2JsGradlePluginIT : BaseGradleIT() {
         }
     }
 
-    @Test
-    fun testKotlinJsSourceMap() {
-        val project = Project("kotlin2JsNoOutputFileProject")
-
-        project.setupWorkingDir()
-
-        project.projectDir.getFileByName("build.gradle").modify {
-            it + "\n" +
-                    "compileKotlin2Js.kotlinOptions.sourceMap = true\n" +
-                    "compileKotlin2Js.kotlinOptions.sourceMapPrefix = \"prefixprefix/\"\n" +
-                    "compileKotlin2Js.kotlinOptions.outputFile = \"\${buildDir}/kotlin2js/main/app.js\"\n"
-        }
-
-        project.build("build") {
-            assertSuccessful()
-
-            val mapFilePath = "build/kotlin2js/main/app.js.map"
-            assertFileExists(mapFilePath)
-            val map = fileInWorkingDir(mapFilePath).readText()
-
-            val sourceFilePath = "prefixprefix/src/main/kotlin/example/Dummy.kt"
-            assertTrue("Source map should contain reference to $sourceFilePath") { map.contains("\"$sourceFilePath\"") }
-        }
-    }
-
-    @Test
-    fun testKotlinJsSourceMapInline() {
-        val project = Project("kotlin2JsProjectWithSourceMapInline")
-
-        project.build("build") {
-            assertSuccessful()
-
-            val mapFilePath = kotlinClassesDir(subproject = "app") + "app.js.map"
-            assertFileExists(mapFilePath)
-            val map = fileInWorkingDir(mapFilePath).readText()
-
-            assertTrue("Source map should contain reference to main.kt") { map.contains("\"./src/main/kotlin/main.kt\"") }
-            assertTrue("Source map should contain reference to foo.kt") { map.contains("\"./src/main/kotlin/foo.kt\"") }
-            assertTrue("Source map should contain source of main.kt") { map.contains("\"fun main(args: Array<String>) {") }
-            assertTrue("Source map should contain source of foo.kt") { map.contains("\"inline fun foo(): String {") }
-        }
-    }
-
     @Test
     fun testDce() {
         val project = Project("kotlin2JsDceProject", minLogLevel = LogLevel.INFO)
@@ -305,6 +113,239 @@ class Kotlin2JsGradlePluginIT : BaseGradleIT() {
             assertTrue(fileInWorkingDir("$pathPrefix/kotlin.js").length() < 500 * 1000, "Looks like kotlin.js file was not minified by DCE")
         }
     }
+}
+
+abstract class AbstractKotlin2JsGradlePluginIT(private val irBackend: Boolean) : BaseGradleIT() {
+    override fun defaultBuildOptions(): BuildOptions =
+        super.defaultBuildOptions().copy(jsIrBackend = irBackend)
+
+    private fun CompiledProject.checkIrCompilationMessage() {
+        if (irBackend) {
+            assertContains(USING_JS_IR_BACKEND_MESSAGE)
+        } else {
+            assertNotContains(USING_JS_IR_BACKEND_MESSAGE)
+        }
+    }
+
+    @Test
+    fun testBuildAndClean() {
+        val project = Project("kotlin2JsProject")
+
+        project.build("build") {
+            assertSuccessful()
+            assertReportExists()
+            checkIrCompilationMessage()
+
+            assertTasksExecuted(
+                ":libraryProject:jarSources",
+                ":mainProject:compileKotlin2Js",
+                ":libraryProject:compileKotlin2Js"
+            )
+
+            assertFileExists("mainProject/web/js/app.js")
+            if (!irBackend) {
+                assertFileExists("mainProject/web/js/lib/kotlin.js")
+                assertFileExists("libraryProject/build/kotlin2js/main/test-library.js")
+                assertFileExists("mainProject/web/js/app.js.map")
+            }
+        }
+
+        project.build("build") {
+            assertSuccessful()
+            assertTasksUpToDate(":mainProject:compileKotlin2Js")
+            assertContainsRegex(":libraryProject:compileTestKotlin2Js (UP-TO-DATE|NO-SOURCE)".toRegex())
+        }
+
+        project.build("clean") {
+            assertSuccessful()
+            assertReportExists()
+
+            // Test that we don't accidentally remove the containing directory
+            // This would fail if we used the default clean task of the copy task
+            assertFileExists("mainProject/web/js/lib")
+
+            assertNoSuchFile("main/project/web/js/app.js.map")
+            assertNoSuchFile("main/project/web/js/example/main.kt")
+        }
+
+        project.build("clean") {
+            assertSuccessful()
+            assertReportExists()
+        }
+    }
+
+    @Test
+    fun testJarIncludesJsDefaultOutput() {
+        val project = Project("kotlin2JsNoOutputFileProject")
+
+        project.build("jar") {
+            assertSuccessful()
+            checkIrCompilationMessage()
+
+            assertTasksExecuted(":compileKotlin2Js")
+            val jarPath = "build/libs/kotlin2JsNoOutputFileProject.jar"
+            assertFileExists(jarPath)
+            val jar = ZipFile(fileInWorkingDir(jarPath))
+            assertEquals(
+                1, jar.entries().asSequence().count { it.name == "kotlin2JsNoOutputFileProject.js" },
+                "The jar should contain an entry `kotlin2JsNoOutputFileProject.js` with no duplicates"
+            )
+        }
+    }
+
+    @Test
+    fun testJarIncludesJsOutputSetExplicitly() {
+        val project = Project("kotlin2JsModuleKind")
+
+        project.build(":jar") {
+            assertSuccessful()
+            checkIrCompilationMessage()
+
+            assertTasksExecuted(":compileKotlin2Js")
+            val jarPath = "build/libs/kotlin2JsModuleKind.jar"
+            assertFileExists(jarPath)
+            val jar = ZipFile(fileInWorkingDir(jarPath))
+            assertEquals(
+                1, jar.entries().asSequence().count { it.name == "app.js" },
+                "The jar should contain an entry `app.js` with no duplicates"
+            )
+        }
+    }
+
+    @Test
+    fun testModuleKind() {
+        val project = Project("kotlin2JsModuleKind")
+
+        project.build("runRhino") {
+            assertSuccessful()
+            checkIrCompilationMessage()
+        }
+    }
+
+    @Test
+    fun testDefaultOutputFile() {
+        val project = Project("kotlin2JsNoOutputFileProject")
+
+        project.build("build") {
+            assertSuccessful()
+            checkIrCompilationMessage()
+            if (irBackend) {
+                assertFileExists(kotlinClassesDir() + "manifest")
+            } else {
+                assertFileExists(kotlinClassesDir() + "kotlin2JsNoOutputFileProject.js")
+            }
+            assertFileExists(kotlinClassesDir(sourceSet = "test") + "kotlin2JsNoOutputFileProject_test.js")
+        }
+    }
+
+    @Test
+    fun testCompileTestCouldAccessProduction() {
+        val project = Project("kotlin2JsProjectWithTests")
+
+        project.build("build") {
+            assertSuccessful()
+            checkIrCompilationMessage()
+
+            assertTasksExecuted(
+                ":compileKotlin2Js",
+                ":compileTestKotlin2Js"
+            )
+            if (irBackend) {
+                assertFileExists("build/kotlin2js/main/manifest")
+            } else {
+                assertFileExists("build/kotlin2js/main/module.js")
+            }
+            assertFileExists("build/kotlin2js/test/module-tests.js")
+        }
+    }
+
+    @Test
+    fun testCompilerTestAccessInternalProduction() {
+        val project = Project("kotlin2JsInternalTest")
+
+        project.build("runRhino") {
+            assertSuccessful()
+            checkIrCompilationMessage()
+        }
+    }
+
+    @Test
+    fun testJsCustomSourceSet() {
+        val project = Project("kotlin2JsProjectWithCustomSourceset")
+
+        project.build("build") {
+            assertSuccessful()
+            checkIrCompilationMessage()
+
+            assertTasksExecuted(
+                ":compileKotlin2Js",
+                ":compileIntegrationTestKotlin2Js"
+            )
+
+            if (!irBackend) {
+                assertFileExists("build/kotlin2js/main/module.js")
+            }
+            assertFileExists("build/kotlin2js/integrationTest/module-inttests.js")
+
+            val jarPath = "build/libs/kotlin2JsProjectWithCustomSourceset-inttests.jar"
+            assertFileExists(jarPath)
+            val jar = ZipFile(fileInWorkingDir(jarPath))
+            assertEquals(
+                1, jar.entries().asSequence().count { it.name == "module-inttests.js" },
+                "The jar should contain an entry `module-inttests.js` with no duplicates"
+            )
+        }
+    }
+
+
+    @Test
+    fun testKotlinJsSourceMap() {
+        // TODO: Support source maps
+        assumeFalse(irBackend)
+
+        val project = Project("kotlin2JsNoOutputFileProject")
+
+        project.setupWorkingDir()
+
+        project.projectDir.getFileByName("build.gradle").modify {
+            it + "\n" +
+                    "compileKotlin2Js.kotlinOptions.sourceMap = true\n" +
+                    "compileKotlin2Js.kotlinOptions.sourceMapPrefix = \"prefixprefix/\"\n" +
+                    "compileKotlin2Js.kotlinOptions.outputFile = \"\${buildDir}/kotlin2js/main/app.js\"\n"
+        }
+
+        project.build("build") {
+            assertSuccessful()
+
+            val mapFilePath = "build/kotlin2js/main/app.js.map"
+            assertFileExists(mapFilePath)
+            val map = fileInWorkingDir(mapFilePath).readText()
+
+            val sourceFilePath = "prefixprefix/src/main/kotlin/example/Dummy.kt"
+            assertTrue("Source map should contain reference to $sourceFilePath") { map.contains("\"$sourceFilePath\"") }
+        }
+    }
+
+    @Test
+    fun testKotlinJsSourceMapInline() {
+        // TODO: Support source maps
+        assumeFalse(irBackend)
+
+        val project = Project("kotlin2JsProjectWithSourceMapInline")
+
+        project.build("build") {
+            assertSuccessful()
+
+            val mapFilePath = kotlinClassesDir(subproject = "app") + "app.js.map"
+            assertFileExists(mapFilePath)
+            val map = fileInWorkingDir(mapFilePath).readText()
+
+            assertTrue("Source map should contain reference to main.kt") { map.contains("\"./src/main/kotlin/main.kt\"") }
+            assertTrue("Source map should contain reference to foo.kt") { map.contains("\"./src/main/kotlin/foo.kt\"") }
+            assertTrue("Source map should contain source of main.kt") { map.contains("\"fun main(args: Array<String>) {") }
+            assertTrue("Source map should contain source of foo.kt") { map.contains("\"inline fun foo(): String {") }
+        }
+    }
 
     /** Issue: KT-18495 */
     @Test
@@ -312,6 +353,7 @@ class Kotlin2JsGradlePluginIT : BaseGradleIT() {
         val project = Project("kotlin2JsProject")
         project.build("build") {
             assertSuccessful()
+            checkIrCompilationMessage()
             assertNotContains("this build assumes a single directory for all classes from a source set")
         }
     }
@@ -320,8 +362,11 @@ class Kotlin2JsGradlePluginIT : BaseGradleIT() {
     fun testIncrementalCompilation() = Project("kotlin2JsICProject").run {
         build("build") {
             assertSuccessful()
-            assertContains(USING_JS_INCREMENTAL_COMPILATION_MESSAGE)
+            checkIrCompilationMessage()
-            assertCompiledKotlinSources(project.relativize(allKotlinFiles))
+            if (!irBackend) { // TODO: Support incremental compilation
+                assertContains(USING_JS_INCREMENTAL_COMPILATION_MESSAGE)
+                assertCompiledKotlinSources(project.relativize(allKotlinFiles))
+            }
         }
 
         build("build") {
@@ -334,9 +379,13 @@ class Kotlin2JsGradlePluginIT : BaseGradleIT() {
         }
         build("build") {
             assertSuccessful()
-            assertContains(USING_JS_INCREMENTAL_COMPILATION_MESSAGE)
+            checkIrCompilationMessage()
-            val affectedFiles = project.projectDir.getFilesByNames("A.kt", "useAInLibMain.kt", "useAInAppMain.kt", "useAInAppTest.kt")
+            // TODO: Support incremental compilation in IR backend
-            assertCompiledKotlinSources(project.relativize(affectedFiles))
+            if (!irBackend) {
+                assertContains(USING_JS_INCREMENTAL_COMPILATION_MESSAGE)
+                val affectedFiles = project.projectDir.getFilesByNames("A.kt", "useAInLibMain.kt", "useAInAppMain.kt", "useAInAppTest.kt")
+                assertCompiledKotlinSources(project.relativize(affectedFiles))
+            }
         }
     }
 
@@ -346,12 +395,14 @@ class Kotlin2JsGradlePluginIT : BaseGradleIT() {
 
         build("build", options = options) {
             assertSuccessful()
+            checkIrCompilationMessage()
             assertNotContains(USING_JS_INCREMENTAL_COMPILATION_MESSAGE)
         }
     }
 
     @Test
     fun testNewKotlinJsPlugin() = with(Project("kotlin-js-plugin-project", GradleVersionRequired.AtLeast("4.10.2"))) {
+        assumeFalse(irBackend) // TODO: Support IR version of kotlinx.html
         setupWorkingDir()
         gradleBuildScript().modify(::transformBuildScriptWithPluginsDsl)
         gradleSettingsScript().modify(::transformBuildScriptWithPluginsDsl)

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsICProject/app/build.gradle

@@ -4,3 +4,9 @@ dependencies {
     compile "org.jetbrains.kotlin:kotlin-stdlib-js:$kotlin_version"
     compile project(":lib")
 }
+
+def isIrBackend = project.findProperty("kotlin.js.useIrBackend")?.toBoolean() ?: false
+if (isIrBackend) {
+    compileKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-klib-dir", "-Xir-only"]
+    compileTestKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-js"]
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsICProject/lib/build.gradle

@@ -3,3 +3,9 @@ apply plugin: 'kotlin2js'
 dependencies {
     compile "org.jetbrains.kotlin:kotlin-stdlib-js:$kotlin_version"
 }
+
+def isIrBackend = project.findProperty("kotlin.js.useIrBackend")?.toBoolean() ?: false
+if (isIrBackend) {
+    compileKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-klib-dir", "-Xir-only"]
+    compileTestKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-js"]
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsInternalTest/build.gradle

@@ -22,11 +22,22 @@ dependencies {
 
 def classesDir = "${buildDir}/classes/kotlin"
 
+def isIrBackend = project.findProperty("kotlin.js.useIrBackend")?.toBoolean() ?: false
+if (isIrBackend) {
+    compileKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-klib-dir", "-Xir-only"]
+    compileTestKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-js"]
+}
+
 task runRhino(type: JavaExec) {
     classpath = sourceSets.main.runtimeClasspath
     workingDir = classesDir
     main = 'org.mozilla.javascript.tools.shell.Main'
-    args = ["-opt", "-1", "-f", "kotlin.js", "-f", "main/kotlin2JsInternalTest.js", "-f", "test/kotlin2JsInternalTest_test.js", "-f", "check.js"]
+    if (isIrBackend) {
+        // IR backend produces a single JS file
+        args = ["-opt", "-1", "test/kotlin2JsInternalTest_test.js", "-f", "check.js"]
+    } else {
+        args = ["-opt", "-1", "-f", "kotlin.js", "-f", "main/kotlin2JsInternalTest.js", "-f", "test/kotlin2JsInternalTest_test.js", "-f", "check.js"]
+    }
 }
 
 build.doLast {

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsInternalTest/src/test/kotlin/tests.kt

@@ -22,6 +22,7 @@ fun <T> assertEquals(e: T, a: T) {
     if (e != a) throw Exception("Expected: $e, actual: $a")
 }
 
+@JsExport
 fun test() {
     assertEquals("CONST", CONST)
 

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsModuleKind/build.gradle

@@ -16,6 +16,10 @@ def outDir = "${buildDir}/kotlin2js/main/"
 compileKotlin2Js.kotlinOptions.moduleKind = "amd"
 compileKotlin2Js.kotlinOptions.outputFile = outDir + "app.js"
 
+if (project.findProperty("kotlin.js.useIrBackend")?.toBoolean() == true) {
+    compileKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-js"]
+}
+
 repositories {
     mavenLocal()
     mavenCentral()

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsModuleKind/src/main/kotlin/org/jetbrains/HelloWorld.kt

@@ -16,4 +16,5 @@
 
 package foo
 
+@JsExport
 fun bar() = "OK"

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsNoOutputFileProject/build.gradle

@@ -17,4 +17,9 @@ repositories {
 
 dependencies {
     compile "org.jetbrains.kotlin:kotlin-stdlib-js:$kotlin_version"
+}
+
+if (project.findProperty("kotlin.js.useIrBackend")?.toBoolean() == true) {
+    compileKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-klib-dir", "-Xir-produce-js", "-Xir-only"]
+    compileTestKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-js"]
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsProject/libraryProject/build.gradle

@@ -31,12 +31,17 @@ def outDir = "${buildDir}/kotlin2js/main/"
 
 compileKotlin2Js.kotlinOptions.outputFile = outDir + "test-library.js"
 
+def isIrBackend = project.findProperty("kotlin.js.useIrBackend")?.toBoolean()
+if (isIrBackend) {
+    compileKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-klib-dir"]
+}
+
 jar {
     from sourceSets.main.allSource
     include "**/*.kt"
 
     from outDir
-    include "**/*.js"
+    include (isIrBackend ? "**/*" : "**/*.js")
 
     manifest {
         attributes(

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsProject/mainProject/build.gradle

@@ -25,6 +25,10 @@ compileKotlin2Js.kotlinOptions.outputFile = "${projectDir}/web/js/app.js"
 compileKotlin2Js.kotlinOptions.suppressWarnings = true
 compileKotlin2Js.kotlinOptions.verbose = true
 
+if (project.findProperty("kotlin.js.useIrBackend")?.toBoolean() == true) {
+    compileKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-js"]
+}
+
 build.doLast {
     configurations.compile.each { File file ->
         copy {

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsProjectWithCustomSourceset/build.gradle

@@ -29,6 +29,12 @@ compileIntegrationTestKotlin2Js.dependsOn compileKotlin2Js
 compileKotlin2Js.kotlinOptions.outputFile = "${buildDir}/kotlin2js/main/module.js"
 compileIntegrationTestKotlin2Js.kotlinOptions.outputFile = "${buildDir}/kotlin2js/integrationTest/module-inttests.js"
 
+def isIrBackend = project.findProperty("kotlin.js.useIrBackend")?.toBoolean() ?: false
+if (isIrBackend) {
+    compileKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-klib-dir", "-Xir-only"]
+    compileIntegrationTestKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-js"]
+}
+
 dependencies {
     compile "org.jetbrains.kotlin:kotlin-stdlib-js:$kotlin_version"
     integrationTestCompile files(file(compileKotlin2Js.kotlinOptions.outputFile).parent)

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsProjectWithTests/build.gradle

@@ -30,3 +30,8 @@ artifacts {
 
 compileKotlin2Js.kotlinOptions.outputFile = "${buildDir}/kotlin2js/main/module.js"
 compileTestKotlin2Js.kotlinOptions.outputFile = "${buildDir}/kotlin2js/test/module-tests.js"
+
+if (project.findProperty("kotlin.js.useIrBackend")?.toBoolean() == true) {
+    compileKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-klib-dir", "-Xir-only"]
+    compileTestKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-js"]
+}

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/tasks/Tasks.kt

@@ -29,8 +29,10 @@ import org.jetbrains.kotlin.gradle.internal.prepareCompilerArguments
 import org.jetbrains.kotlin.gradle.internal.tasks.TaskWithLocalState
 import org.jetbrains.kotlin.gradle.internal.tasks.allOutputFiles
 import org.jetbrains.kotlin.gradle.logging.*
-import org.jetbrains.kotlin.gradle.plugin.*
 import org.jetbrains.kotlin.gradle.plugin.COMPILER_CLASSPATH_CONFIGURATION_NAME
+import org.jetbrains.kotlin.gradle.plugin.KotlinMultiplatformPluginWrapper
+import org.jetbrains.kotlin.gradle.plugin.KotlinPlatformPluginBase
+import org.jetbrains.kotlin.gradle.plugin.PLUGIN_CLASSPATH_CONFIGURATION_NAME
 import org.jetbrains.kotlin.gradle.plugin.mpp.associateWithTransitiveClosure
 import org.jetbrains.kotlin.gradle.plugin.mpp.ownModuleName
 import org.jetbrains.kotlin.gradle.report.BuildReportMode
@@ -49,6 +51,7 @@ import javax.inject.Inject
 const val KOTLIN_BUILD_DIR_NAME = "kotlin"
 const val USING_JVM_INCREMENTAL_COMPILATION_MESSAGE = "Using Kotlin/JVM incremental compilation"
 const val USING_JS_INCREMENTAL_COMPILATION_MESSAGE = "Using Kotlin/JS incremental compilation"
+const val USING_JS_IR_BACKEND_MESSAGE = "Using Kotlin/JS IR backend"
 
 abstract class AbstractKotlinCompileTool<T : CommonToolArguments>
     : AbstractCompile(),
@@ -553,9 +556,34 @@ open class Kotlin2JsCompile : AbstractKotlinCompile<K2JSCompilerArguments>(), Ko
             return friendPaths.filter { filter(File(it)) }
         }
 
+    private fun isHybridKotlinJsLibrary(file: File): Boolean =
+        LibraryUtils.isKotlinJavascriptLibrary(file) && LibraryUtils.isKotlinJavascriptIrLibrary(file)
+
+    private fun KotlinJsOptions.isPreIrBackendDisabled(): Boolean =
+        listOf(
+            "-Xir-only",
+            "-Xir-produce-js",
+            "-Xir-produce-klib-file"
+        ).any(freeCompilerArgs::contains)
+
+    private fun KotlinJsOptions.isIrBackendEnabled(): Boolean =
+        listOf(
+            "-Xir-produce-klib-dir",
+            "-Xir-produce-js",
+            "-Xir-produce-klib-file"
+        ).any(freeCompilerArgs::contains)
+
+    // Kotlin/JS can operate in 3 modes:
+    //  1) purely pre-IR backend
+    //  2) purely IR backend
+    //  3) hybrid pre-IR and IR backend. Can only accept libraries with both JS and IR parts.
     private val libraryFilter: (File) -> Boolean
-        get() = if ("-Xir" in kotlinOptions.freeCompilerArgs) {
+        get() = if (kotlinOptions.isIrBackendEnabled()) {
-            LibraryUtils::isKotlinJavascriptIrLibrary
+            if (kotlinOptions.isPreIrBackendDisabled()) {
+                LibraryUtils::isKotlinJavascriptIrLibrary
+            } else {
+                ::isHybridKotlinJsLibrary
+            }
         } else {
             LibraryUtils::isKotlinJavascriptLibrary
         }
@@ -566,10 +594,9 @@ open class Kotlin2JsCompile : AbstractKotlinCompile<K2JSCompilerArguments>(), Ko
         logger.debug("Calling compiler")
         destinationDir.mkdirs()
 
-        if ("-Xir" in args.freeArgs) {
+        if (kotlinOptions.isIrBackendEnabled()) {
-            logger.kotlinDebug("Using JS IR backend")
+            logger.info(USING_JS_IR_BACKEND_MESSAGE)
             incremental = false
-            args.freeArgs += "-Xir-legacy-gradle-plugin-compatibility"
         }
 
         val dependencies = compileClasspath

libraries/tools/kotlin-maven-plugin/src/main/java/org/jetbrains/kotlin/maven/K2JSCompilerMojo.java

@@ -105,8 +105,9 @@ public class K2JSCompilerMojo extends KotlinCompileMojoBase<K2JSCompilerArgument
         arguments.setMetaInfo(metaInfo);
         arguments.setModuleKind(moduleKind);
         arguments.setMain(main);
-        arguments.setIrBackend(useIrBackend);
+        arguments.setIrOnly(useIrBackend);
-        arguments.setIrLegacyGradlePluginCompatibility(true);
+        arguments.setIrProduceJs(useIrBackend);
+        arguments.setIrProduceKlibDir(useIrBackend);
 
         List<String> libraries;
         try {

prepare/compiler/build.gradle.kts

@@ -91,7 +91,6 @@ val distLibraryProjects = listOfNotNull(
     ":kotlin-stdlib-js-ir".takeIf { kotlinBuildProperties.jsIrDist },
     ":kotlin-source-sections-compiler-plugin",
     ":kotlin-test:kotlin-test-js",
-    ":kotlin-test:kotlin-test-js-ir".takeIf { kotlinBuildProperties.jsIrDist },
     ":kotlin-test:kotlin-test-junit",
     ":kotlin-test:kotlin-test-junit5",
     ":kotlin-test:kotlin-test-jvm",
@@ -114,7 +113,6 @@ val distSourcesProjects = listOfNotNull(
     ":kotlin-script-runtime",
     ":kotlin-stdlib-js-ir".takeIf { kotlinBuildProperties.jsIrDist },
     ":kotlin-test:kotlin-test-js",
-    ":kotlin-test:kotlin-test-js-ir".takeIf { kotlinBuildProperties.jsIrDist },
     ":kotlin-test:kotlin-test-junit",
     ":kotlin-test:kotlin-test-junit5",
     ":kotlin-test:kotlin-test-jvm",
@@ -149,7 +147,7 @@ dependencies {
     libraries(intellijDep()) { includeIntellijCoreJarDependencies(project) { it.startsWith("trove4j") } }
     libraries(commonDep("io.ktor", "ktor-network"))
     libraries(kotlinStdlib("jdk8"))
-    libraries(kotlinStdlib("js"))
+    libraries(kotlinStdlib("js", "distLibrary"))
 
     distLibraryProjects.forEach {
         libraries(project(it)) { isTransitive = false }

settings.gradle

@@ -274,7 +274,6 @@ if (flags.inJpsBuildIdeaSync) {
             ":kotlin-stdlib-common",
             ":kotlin-stdlib",
             ":kotlin-stdlib-js",
-            ":kotlin-test:kotlin-test-js-ir",
             ":kotlin-stdlib-js-ir",
             ":kotlin-stdlib-jdk7",
             ":kotlin-stdlib-jdk8",
@@ -289,7 +288,6 @@ if (flags.inJpsBuildIdeaSync) {
     project(':kotlin-stdlib').projectDir = "$rootDir/libraries/stdlib/jvm" as File
     project(':kotlin-stdlib-js').projectDir = "$rootDir/libraries/stdlib/js-v1" as File
     project(':kotlin-stdlib-js-ir').projectDir = "$rootDir/libraries/stdlib/js-ir" as File
-    project(':kotlin-test:kotlin-test-js-ir').projectDir = "$rootDir/libraries/kotlin.test/js-ir" as File
     project(':kotlin-stdlib-jdk7').projectDir = "$rootDir/libraries/stdlib/jdk7" as File
     project(':kotlin-stdlib-jdk8').projectDir = "$rootDir/libraries/stdlib/jdk8" as File
     project(':kotlin-stdlib:samples').projectDir = "$rootDir/libraries/stdlib/samples" as File