Add a redundancy warning to skiko.js for k/wasm target (#5134)

skiko.js used to be required for k/wasm projects. But some time ago it
was refactored to use skiko.mjs, so skiko.js is not needed anymore (for
k/wasm, still needed for k/js). But there are k/wasm projects still
including skiko.js in index.html which leads to extra loading time. The
intention is to notify them without causing 404 errors for now.

## Testing
- updated a test
- tested manually

<img width="856" alt="Screenshot 2024-09-10 at 15 34 41"
src="https://github.com/user-attachments/assets/9ad9b790-d3fa-4907-b9ee-f5e682f38858">

## Release Notes
### Highlights - Web
- `skiko.js` is redundant in case of K/Wasm Compose for Web applications
and it can be removed from index.html files to not load redundant files.
We are going to remove `skiko.js` from the k/wasm distribution in the
future releases. `skiko.js` is still needed in case of K/JS Compose for
Web apps.

(cherry picked from commit 8b56020c81)

gradle-plugins/compose/src/main/kotlin/org/jetbrains/compose/web/internal/configureWebApplication.kt

@@ -12,10 +12,12 @@ import org.gradle.api.artifacts.UnresolvedDependency
 import org.gradle.api.artifacts.component.ModuleComponentIdentifier
 import org.gradle.api.file.DuplicatesStrategy
 import org.gradle.api.provider.Provider
+import org.gradle.api.tasks.Copy
 import org.gradle.language.jvm.tasks.ProcessResources
 import org.jetbrains.compose.ComposeBuildConfig
 import org.jetbrains.compose.ComposeExtension
 import org.jetbrains.compose.internal.utils.detachedComposeDependency
+import org.jetbrains.compose.internal.utils.file
 import org.jetbrains.compose.internal.utils.registerTask
 import org.jetbrains.compose.web.WebExtension
 import org.jetbrains.compose.web.tasks.UnpackSkikoWasmRuntimeTask
@@ -71,7 +73,8 @@ internal fun configureWebApplication(
         it.addLater(skikoJsWasmRuntimeDependency)
     }
 
-    val unpackedRuntimeDir = project.layout.buildDirectory.dir("compose/skiko-wasm")
+    val unpackedRuntimeDir = project.layout.buildDirectory.dir("compose/skiko-for-web-runtime")
+    val processedRuntimeDir = project.layout.buildDirectory.dir("compose/skiko-runtime-processed-wasmjs")
     val taskName = "unpackSkikoWasmRuntime"
 
     val unpackRuntime = project.registerTask<UnpackSkikoWasmRuntimeTask>(taskName) {
@@ -83,6 +86,25 @@ internal fun configureWebApplication(
         outputDir.set(unpackedRuntimeDir)
     }
 
+    val processSkikoRuntimeForKWasm = project.registerTask<Copy>("processSkikoRuntimeForKWasm") {
+        dependsOn(unpackRuntime)
+        from(unpackedRuntimeDir)
+        into(processedRuntimeDir)
+
+        doLast {
+            // TODO: in the next versions we can simply filter skiko.js out for k/wasm target
+            processedRuntimeDir.file("skiko.js").get().apply {
+                asFile.appendText("\n\n// Warn about skiko.js redundancy in case of K/Wasm target:\n")
+                asFile.appendText(
+                    """console.warn("Note: skiko.js is redundant in K/Wasm Compose for Web applications. 
+                        |Consider removing it from index.html, 
+                        |it will be removed from the distribution in next Compose Multiplatform versions");
+                        """.trimMargin().replace("\n", "")
+                )
+            }
+        }
+    }
+
     targets.forEach { target ->
         target.compilations.all { compilation ->
             // `wasmTargetType` is available starting with kotlin 1.9.2x
@@ -92,8 +114,8 @@ internal fun configureWebApplication(
                 // So that’s why we need to provide skiko.mjs and skiko.wasm only for webpack, but not in the final dist.
                 compilation.binaries.all {
                     it.linkSyncTask.configure {
-                        it.dependsOn(unpackRuntime)
-                        it.from.from(unpackedRuntimeDir)
+                        it.dependsOn(processSkikoRuntimeForKWasm)
+                        it.from.from(processedRuntimeDir)
                     }
                 }
             } else {

gradle-plugins/compose/src/test/kotlin/org/jetbrains/compose/test/tests/integration/GradlePluginTest.kt

@@ -46,6 +46,7 @@ class GradlePluginTest : GradlePluginTestBase() {
         jsCanvasEnabled(true)
         gradle(":build").checks {
             check.taskSuccessful(":unpackSkikoWasmRuntime")
+            check.taskSuccessful(":processSkikoRuntimeForKWasm")
             check.taskSuccessful(":compileKotlinJs")
             check.taskSuccessful(":compileKotlinWasmJs")
             check.taskSuccessful(":wasmJsBrowserDistribution")
@@ -69,6 +70,7 @@ class GradlePluginTest : GradlePluginTestBase() {
                 val distributionFiles = listFiles()!!.map { it.name }.toList()
                 assertTrue(distributionFiles.contains("skiko.wasm"))
                 assertTrue(distributionFiles.contains("skiko.js"))
+                assertFalse(this.resolve("skiko.js").readText().contains("skiko.js is redundant"))
             }
         }
     }