[Gradle] Pass Android-related sources to KotlinSourceSet instead task

Setting sources through compile task is not compatible with
Multiplatform K2 because for such sources no K2 Fragment relations
will be set and compilation will fail.

^KT-63753 Verification Pending

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

@@ -961,4 +961,58 @@ class KotlinAndroidMppIT : KGPBaseTest() {
         }
     }
 
+    @DisplayName("KT-63753: K2 File \"does not belong to any module\" when it is generated by `registerJavaGeneratingTask` in AGP")
+    @GradleAndroidTest
+    fun sourceGenerationTaskAddedToAndroidVariant(
+        gradleVersion: GradleVersion,
+        agpVersion: String,
+        jdkVersion: JdkVersions.ProvidedJdk
+    ) {
+        project(
+            "new-mpp-android", gradleVersion,
+            defaultBuildOptions.copy(androidVersion = agpVersion),
+            buildJdk = jdkVersion.location
+        ) {
+            // Hacks for TODO: KT-65426
+            val appPath = subProject("app").projectPath
+            appPath.resolve("src/main/java/app/example/com/app_sample").deleteRecursively()
+            appPath.resolve("src/commonMain/kotlin/A.kt").replaceText("expect fun f(): Unit", "")
+
+            // Code copied from the reproducer from KT-63753
+            subProject("app").buildGradleKts.appendText(
+                """
+                    
+                    abstract class FileGeneratingTask : DefaultTask() {
+                        @get:OutputDirectory
+                        abstract val outputDir: DirectoryProperty
+
+                        @TaskAction
+                        fun taskAction() {
+                            val outputDirFile = outputDir.asFile.get()
+                            outputDirFile.mkdirs()
+                            val file = File(outputDirFile, "Test.kt")
+                            val text = ""${'"'}
+                                val hello = "World!"
+                            ""${'"'}
+                            file.writeText(text)
+                        }
+                    }
+                    
+                    android {
+                        applicationVariants.configureEach {
+                            val variant = this
+                            val outputDir = File(buildDir, "generateExternalFile/${'$'}{variant.dirName}")
+                            val task = project.tasks.register("generateExternalFile${'$'}{variant.name.capitalize()}", FileGeneratingTask::class.java) {
+                                this.outputDir.set(outputDir)
+                            }
+                            variant.registerJavaGeneratingTask(task, outputDir)
+                        }                    
+                    }
+                """.trimIndent()
+            )
+            build(":app:compileDebugKotlinAndroidApp") {
+                assertTasksExecuted(":app:compileDebugKotlinAndroidApp")
+            }
+        }
+    }
 }

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/targets/android/AndroidProjectHandler.kt

@@ -231,10 +231,12 @@ internal class AndroidProjectHandler(
         val javaTask = variantData.javaCompileProvider
         @Suppress("UNCHECKED_CAST") val kotlinTask = compilation.compileTaskProvider as TaskProvider<KotlinCompile>
         compilation.androidVariant.forEachJavaSourceDir { sources ->
-            kotlinTask.configure {
-                it.setSource(sources.dir)
-                it.dependsOn(sources)
-            }
+            // It is important to pass exactly `sources.dir` as provider with explicit task dependency
+            // Because of the following bugs:
+            // * https://github.com/gradle/gradle/issues/27881 ConfigurableFileTree.from() doesn't preserve Task Dependencies
+            // * https://github.com/gradle/gradle/issues/27882 SourceDirectorySet doesn't accept ConfigurableFileTree
+            val sourceDirWithTaskDependencies = project.filesProvider(sources) { sources.dir }
+            compilation.defaultSourceSet.kotlin.srcDir(sourceDirWithTaskDependencies)
         }
         wireKotlinTasks(project, compilation, androidPlugin, androidExt, variantData, javaTask, kotlinTask)
     }