[JS IR] Generate special region comments at the start and the end of each file block

It allows to fold these blocks and navigate to them in the IDEA.

Also, this commit adds compiler configuration keys to control generating comments with paths for file blocks,
and now generating such comments is enabled only in our tests.

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformer.kt

@@ -31,34 +31,52 @@ class IrModuleToJsTransformer(
 ) {
     val moduleName = backendContext.configuration[CommonConfigurationKeys.MODULE_NAME]!!
     private val moduleKind = backendContext.configuration[JSConfigurationKeys.MODULE_KIND]!!
+    private val generateRegionComments = backendContext.configuration.getBoolean(JSConfigurationKeys.GENERATE_REGION_COMMENTS)
 
     private fun generateModuleBody(module: IrModuleFragment, context: JsGenerationContext): List<JsStatement> {
         val statements = mutableListOf<JsStatement>().also {
             if (!generateScriptModule) it += JsStringLiteral("use strict").makeStmt()
         }
 
-        val preDeclarationBlock = JsBlock()
-        val postDeclarationBlock = JsBlock()
+        val preDeclarationBlock = JsGlobalBlock()
+        val postDeclarationBlock = JsGlobalBlock()
 
-        statements += preDeclarationBlock
+        statements.addWithComment("block: pre-declaration", preDeclarationBlock)
+
+        val generateFilePaths = backendContext.configuration.getBoolean(JSConfigurationKeys.GENERATE_COMMENTS_WITH_FILE_PATH)
 
         module.files.forEach {
             val fileStatements = it.accept(IrFileToJsTransformer(), context).statements
             if (fileStatements.isNotEmpty()) {
-                statements.add(JsSingleLineComment("file: ${it.path}"))
+                var startComment = ""
+
+                if (generateRegionComments) {
+                    startComment = "region "
+                }
+
+                if (generateRegionComments || generateFilePaths) {
+                    startComment += "file: ${it.path}"
+                }
+
+                if (startComment.isNotEmpty()) {
+                    statements.add(JsSingleLineComment(startComment))
+                }
 
                 statements.addAll(fileStatements)
+                statements.endRegion()
             }
         }
 
         // sort member forwarding code
         processClassModels(context.staticContext.classModels, preDeclarationBlock, postDeclarationBlock)
 
-        statements += postDeclarationBlock
-        statements += context.staticContext.initializerBlock
+        statements.addWithComment("block: post-declaration", postDeclarationBlock.statements)
+        statements.addWithComment("block: init", context.staticContext.initializerBlock.statements)
 
         if (backendContext.hasTests) {
+            statements.startRegion("block: tests")
             statements += JsInvocation(context.getNameForStaticFunction(backendContext.testContainer).makeRef()).makeStmt()
+            statements.endRegion()
         }
 
         return statements
@@ -108,18 +126,18 @@ class IrModuleToJsTransformer(
 
         if (generateScriptModule) {
             with(program.globalBlock) {
-                statements += importStatements
+                statements.addWithComment("block: imports", importStatements)
                 statements += moduleBody
-                statements += exportStatements
+                statements.addWithComment("block: exports", exportStatements)
             }
         } else {
             with(rootFunction) {
                 parameters += JsParameter(internalModuleName)
                 parameters += importedJsModules.map { JsParameter(it.internalName) }
                 with(body) {
-                    statements += importStatements
+                    statements.addWithComment("block: imports", importStatements)
                     statements += moduleBody
-                    statements += exportStatements
+                    statements.addWithComment("block: exports", exportStatements)
                     statements += generateCallToMain(rootContext)
                     statements += JsReturn(internalModuleName.makeRef())
                 }
@@ -229,4 +247,30 @@ class IrModuleToJsTransformer(
             declarationHandler
         )
     }
+
+    private fun MutableList<JsStatement>.startRegion(description: String = "") {
+        if (generateRegionComments) {
+            this += JsSingleLineComment("region $description")
+        }
+    }
+
+    private fun MutableList<JsStatement>.endRegion() {
+        if (generateRegionComments) {
+            this += JsSingleLineComment("endregion")
+        }
+    }
+
+    private fun MutableList<JsStatement>.addWithComment(regionDescription: String = "", block: JsBlock) {
+        startRegion(regionDescription)
+        this += block
+        endRegion()
+    }
+
+    private fun MutableList<JsStatement>.addWithComment(regionDescription: String = "", statements: List<JsStatement>) {
+        if (statements.isEmpty()) return
+
+        startRegion(regionDescription)
+        this += statements
+        endRegion()
+    }
 }

js/js.frontend/src/org/jetbrains/kotlin/js/config/JSConfigurationKeys.java

@@ -75,4 +75,10 @@ public class JSConfigurationKeys {
 
     public static final CompilerConfigurationKey<Boolean> DEVELOPER_MODE =
             CompilerConfigurationKey.create("enables additional checkers");
+
+    public static final CompilerConfigurationKey<Boolean> GENERATE_COMMENTS_WITH_FILE_PATH =
+            CompilerConfigurationKey.create("generate comments with file path at the start of each file block");
+
+    public static final CompilerConfigurationKey<Boolean> GENERATE_REGION_COMMENTS =
+            CompilerConfigurationKey.create("generate special comments at the start and the end of each file block, it allows to fold them and navigate to them in the IDEA");
 }

js/js.tests/test/org/jetbrains/kotlin/js/test/BasicBoxTest.kt

@@ -55,16 +55,15 @@ import org.jetbrains.kotlin.serialization.js.JsModuleDescriptor
 import org.jetbrains.kotlin.serialization.js.JsSerializerProtocol
 import org.jetbrains.kotlin.serialization.js.KotlinJavascriptSerializationUtil
 import org.jetbrains.kotlin.serialization.js.ModuleKind
-import org.jetbrains.kotlin.test.InTextDirectivesUtils
-import org.jetbrains.kotlin.test.KotlinTestUtils
-import org.jetbrains.kotlin.test.TestFiles
-import org.jetbrains.kotlin.test.KotlinTestWithEnvironment
-import org.jetbrains.kotlin.test.TargetBackend
+import org.jetbrains.kotlin.test.*
 import org.jetbrains.kotlin.utils.DFS
 import org.jetbrains.kotlin.utils.JsMetadataVersion
 import org.jetbrains.kotlin.utils.KotlinJavascriptMetadata
 import org.jetbrains.kotlin.utils.KotlinJavascriptMetadataUtils
-import java.io.*
+import java.io.ByteArrayOutputStream
+import java.io.Closeable
+import java.io.File
+import java.io.PrintStream
 import java.lang.Boolean.getBoolean
 import java.nio.charset.Charset
 import java.util.regex.Pattern
@@ -672,6 +671,8 @@ abstract class BasicBoxTest(
 
         configuration.put(JSConfigurationKeys.TYPED_ARRAYS_ENABLED, typedArraysEnabled)
 
+        configuration.put(JSConfigurationKeys.GENERATE_REGION_COMMENTS, true)
+
         return JsConfig(project, configuration, METADATA_CACHE, (JsConfig.JS_STDLIB + JsConfig.JS_KOTLIN_TEST).toSet())
     }