[K/JS] Add warning for ES-modules on the klibgen stage on the uniqueness of the exported names from the module

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

@@ -356,6 +356,19 @@ class Kotlin2JsIrGradlePluginIT : KGPBaseTest() {
         }
     }
 
+    @DisplayName("klib compilation with the declarations name clash")
+    @GradleTest
+    fun testProjectWithExportedNamesClash(gradleVersion: GradleVersion) {
+        project("kotlin-js-invalid-project-with-exported-clash", gradleVersion) {
+            build("compileKotlinJs") {
+                assertOutputContains("""
+                   |There are clashes of declaration names that annotated with @JsExport in module 'kotlin-js-invalid-project-with-exported-clash'.
+                   |  * Next files contain declarations with @JsExport and name 'best'
+                """.trimMargin())
+            }
+        }
+    }
+
     @DisplayName("per-file with the  declarations validation")
     @GradleTest
     fun testPerFileProjectWithResultFilesClash(gradleVersion: GradleVersion) {

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin-js-invalid-project-with-exported-clash/build.gradle.kts

@@ -0,0 +1,16 @@
+plugins {
+    kotlin("js")
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+kotlin {
+    js(IR) {
+        useEsModules()
+        binaries.executable()
+        nodejs()
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin-js-invalid-project-with-exported-clash/gradle.properties

@@ -0,0 +1,7 @@
+kotlin.tests.individualTaskReports=true
+kotlin.incremental=false
+kotlin.incremental.js=false
+kotlin.incremental.js.ir=false
+kotlin.incremental.js.klib=false
+kotlin.incremental.multiplatform=false
+kotlin.incremental.useClasspathSnapshot=false

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin-js-invalid-project-with-exported-clash/src/main/kotlin/base1/Base.kt

@@ -0,0 +1,11 @@
+/*
+ * 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 first
+
+@JsExport
+fun best(): Int {
+    return 42
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin-js-invalid-project-with-exported-clash/src/main/kotlin/base2/base.kt

@@ -0,0 +1,10 @@
+/*
+ * 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 second
+
+@JsExport
+@JsName("best")
+public val foo = 44