JS: add DCE devmode. Fix mapping paths in source maps

See KT-20210, KT-21307

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

@@ -2,7 +2,6 @@ package org.jetbrains.kotlin.gradle
 
 import org.gradle.api.logging.LogLevel
 import org.jetbrains.kotlin.gradle.tasks.USING_EXPERIMENTAL_JS_INCREMENTAL_COMPILATION_MESSAGE
-import org.jetbrains.kotlin.gradle.util.allKotlinFiles
 import org.jetbrains.kotlin.gradle.util.getFileByName
 import org.jetbrains.kotlin.gradle.util.modify
 import org.junit.Test
@@ -223,11 +222,36 @@ class Kotlin2JsGradlePluginIT : BaseGradleIT() {
         val project = Project("kotlin2JsDceProject", "2.10", minLogLevel = LogLevel.INFO)
 
         project.build("runRhino") {
-            println(output)
             assertSuccessful()
             val pathPrefix = "mainProject/build/min"
             assertFileExists("$pathPrefix/exampleapp.js.map")
             assertFileExists("$pathPrefix/examplelib.js.map")
+            assertFileContains("$pathPrefix/exampleapp.js.map", "\"../../src/main/kotlin/exampleapp/main.kt\"")
+
+            assertFileExists("$pathPrefix/kotlin.js")
+            assertTrue(fileInWorkingDir("$pathPrefix/kotlin.js").length() < 500 * 1000, "Looks like kotlin.js file was not minified by DCE")
+        }
+    }
+
+    @Test
+    fun testDceDevMode() {
+        val project = Project("kotlin2JsDceProject", "2.10", minLogLevel = LogLevel.INFO)
+
+        project.setupWorkingDir()
+        File(project.projectDir, "mainProject/build.gradle").modify {
+            it + "\n" +
+            "runDceKotlinJs.dceOptions.devMode = true\n"
+        }
+
+        project.build("runRhino") {
+            assertSuccessful()
+            val pathPrefix = "mainProject/build/min"
+            assertFileExists("$pathPrefix/exampleapp.js.map")
+            assertFileExists("$pathPrefix/examplelib.js.map")
+            assertFileContains("$pathPrefix/exampleapp.js.map", "\"../../src/main/kotlin/exampleapp/main.kt\"")
+
+            assertFileExists("$pathPrefix/kotlin.js")
+            assertTrue(fileInWorkingDir("$pathPrefix/kotlin.js").length() > 1000 * 1000, "Looks like kotlin.js file was minified by DCE")
         }
     }
 

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinJsDceOptions.kt

@@ -3,4 +3,10 @@
 package org.jetbrains.kotlin.gradle.dsl
 
 interface KotlinJsDceOptions  : org.jetbrains.kotlin.gradle.dsl.KotlinCommonToolOptions {
+
+    /**
+     * Development mode: don't strip out any code, just copy dependencies and remap source maps
+     * Default value: false
+     */
+     var devMode: kotlin.Boolean
 }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinJsDceOptionsBase.kt

@@ -19,10 +19,16 @@ internal abstract class KotlinJsDceOptionsBase : org.jetbrains.kotlin.gradle.dsl
         get() = verboseField ?: false
         set(value) { verboseField = value }
 
+    private var devModeField: kotlin.Boolean? = null
+    override var devMode: kotlin.Boolean
+        get() = devModeField ?: false
+        set(value) { devModeField = value }
+
     internal open fun updateArguments(args: org.jetbrains.kotlin.cli.common.arguments.K2JSDceArguments) {
         allWarningsAsErrorsField?.let { args.allWarningsAsErrors = it }
         suppressWarningsField?.let { args.suppressWarnings = it }
         verboseField?.let { args.verbose = it }
+        devModeField?.let { args.devMode = it }
     }
 }
 
@@ -30,4 +36,5 @@ internal fun org.jetbrains.kotlin.cli.common.arguments.K2JSDceArguments.fillDefa
     allWarningsAsErrors = false
     suppressWarnings = false
     verbose = false
+    devMode = false
 }