[JS IR] Add -Xgenerate-dts CLI argument

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

@@ -125,6 +125,12 @@ class K2JSCompilerArguments : CommonCompilerArguments() {
     @Argument(value = "-Xir-only", description = "Disables pre-IR backend")
     var irOnly: Boolean by FreezableVar(false)
 
+    @Argument(
+        value = "-Xgenerate-dts",
+        description = "Generate TypeScript declarations .d.ts file alongside JS file. Available in IR backend only."
+    )
+    var generateDts: Boolean by FreezableVar(false)
+
     @GradleOption(DefaultValues.BooleanTrueDefault::class)
     @Argument(value = "-Xtyped-arrays", description = "Translate primitive arrays to JS typed arrays")
     var typedArrays: Boolean by FreezableVar(true)

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

@@ -45,6 +45,7 @@ import org.jetbrains.kotlin.util.Logger
 import org.jetbrains.kotlin.utils.JsMetadataVersion
 import org.jetbrains.kotlin.utils.KotlinPaths
 import org.jetbrains.kotlin.utils.PathUtil
+import org.jetbrains.kotlin.utils.fileUtils.withReplacedExtensionOrNull
 import org.jetbrains.kotlin.utils.join
 import java.io.File
 import java.io.IOException
@@ -208,6 +209,10 @@ class K2JsIrCompiler : CLICompiler<K2JSCompilerArguments>() {
             )
 
             outputFile.writeText(compiledModule.jsCode)
+            if (arguments.generateDts) {
+                val dtsFile = outputFile.withReplacedExtensionOrNull(outputFile.extension, "d.ts")!!
+                dtsFile.writeText(compiledModule.tsDefinitions ?: error("No ts definitions"))
+            }
         }
 
         return OK

compiler/testData/cli/js/jsExtraHelp.out

@@ -3,6 +3,7 @@ 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
+  -Xgenerate-dts             Generate TypeScript declarations .d.ts file alongside JS file. Available in IR backend only.
   -Xir-only                  Disables pre-IR backend
   -Xir-produce-js            Generates JS file using IR backend. Also disables pre-IR backend
   -Xir-produce-klib-dir      Generate unpacked KLIB into parent directory of output JS file.

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

@@ -13,7 +13,21 @@ import java.util.zip.ZipFile
 import kotlin.test.assertEquals
 import kotlin.test.assertTrue
 
-class Kotlin2JsIrGradlePluginIT : AbstractKotlin2JsGradlePluginIT(true)
+class Kotlin2JsIrGradlePluginIT : AbstractKotlin2JsGradlePluginIT(true) {
+    @Test
+    fun generateDts() {
+        val project = Project("kotlin2JsIrDtsGeneration")
+        project.build("build") {
+            assertSuccessful()
+            checkIrCompilationMessage()
+
+            assertFileExists("build/kotlin2js/main/lib.js")
+            val dts = fileInWorkingDir("build/kotlin2js/main/lib.d.ts")
+            assert(dts.exists())
+            assert(dts.readText().contains("function bar(): string"))
+        }
+    }
+}
 
 class Kotlin2JsGradlePluginIT : AbstractKotlin2JsGradlePluginIT(false) {
     @Test
@@ -119,7 +133,7 @@ abstract class AbstractKotlin2JsGradlePluginIT(private val irBackend: Boolean) :
     override fun defaultBuildOptions(): BuildOptions =
         super.defaultBuildOptions().copy(jsIrBackend = irBackend)
 
-    private fun CompiledProject.checkIrCompilationMessage() {
+    protected fun CompiledProject.checkIrCompilationMessage() {
         if (irBackend) {
             assertContains(USING_JS_IR_BACKEND_MESSAGE)
         } else {

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsIrDtsGeneration/build.gradle

@@ -0,0 +1,27 @@
+buildscript {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+    }
+
+    dependencies {
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+apply plugin: "kotlin2js"
+apply plugin: 'java'
+
+def outDir = "${buildDir}/kotlin2js/main/"
+compileKotlin2Js.kotlinOptions.moduleKind = "plain"
+compileKotlin2Js.kotlinOptions.outputFile = outDir + "lib.js"
+compileKotlin2Js.kotlinOptions.freeCompilerArgs += ["-Xir-produce-js", "-Xgenerate-dts"]
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+dependencies {
+    compile "org.jetbrains.kotlin:kotlin-stdlib-js:$kotlin_version"
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin2JsIrDtsGeneration/src/main/kotlin/HelloWorld.kt

@@ -0,0 +1,9 @@
+/*
+ * 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 foo
+
+@JsExport
+fun bar() = "OK"