[Gradle] Fix KGP removes resource-producing task dependency

Previously, we tried to sync existing Java SourceSet resources into
KotlinSourceSet and then replace Java one from Kotlin. For such an
approach, we called 'files' on existing resources, but this does not
carry information about producing task dependency.

This fix goes a little further and just replaces default KotlinSourceSet
 'resources' SourceDirectorySet with a similar object from Java
 SourceSet, so any change to Java or Kotlin resources is reflected in
 both.

^KT-62490 Verification Pending

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

@@ -60,7 +60,7 @@ class ResourcesIT : KGPBaseTest() {
             build("assemble")
         }
     }
-    
+
     @GradleTest
     @DisplayName("KT-60459: should not overwrite custom resource directories")
     @JvmGradlePluginTests
@@ -107,4 +107,52 @@ class ResourcesIT : KGPBaseTest() {
             }
         }
     }
+
+    @GradleTest
+    @DisplayName("KT-62490: should not drop reference to task producing resources")
+    @JvmGradlePluginTests
+    fun keepReferenceToResourcesProducingTask(gradleVersion: GradleVersion) {
+        project("kt-62490", gradleVersion) {
+            build("processResources") {
+                assertTasksExecuted(":customResGenerator")
+                assertFileInProjectExists("build/custom-res/myres.txt")
+            }
+        }
+    }
+
+    @GradleTest
+    @DisplayName("KT-62490: should keep previously configured Kotlin resources")
+    @JvmGradlePluginTests
+    fun keepConfiguredKotlinResources(gradleVersion: GradleVersion) {
+        project(
+            "kt-62490",
+            gradleVersion,
+            buildOptions = defaultBuildOptions.suppressDeprecationWarningsOn(
+                reason = "KT-64462: Gradle complains about already created configurations",
+                predicate = { gradleVersion >= GradleVersion.version(TestVersions.Gradle.G_8_2) }
+            )
+        ) {
+            buildGradleKts.appendText(
+                //language=kotlin
+                """
+                |
+                |val customResGenerator1 = tasks.register<CustomResGenerator>("customResGenerator1") {
+                |    outputFile.value(project.layout.buildDirectory.dir("custom-res-1"))
+                |}
+                |project.extensions.getByType<org.jetbrains.kotlin.gradle.dsl.KotlinProjectExtension>()
+                |    .sourceSets.create("x").resources.srcDir(customResGenerator1)
+                |sourceSets.create("x")
+                """.trimMargin()
+            )
+
+            val xResFile = projectPath.resolve("src/x/resources").resolve("test.txt").toFile()
+            xResFile.parentFile.mkdirs()
+            xResFile.writeText("some resource")
+
+            build("processXResources", enableGradleDebug = true) {
+                assertTasksExecuted(":customResGenerator1")
+                assertFileInProjectExists("build/custom-res-1/myres.txt")
+            }
+        }
+    }
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kt-62490/build.gradle.kts

@@ -0,0 +1,24 @@
+plugins {
+    `java`
+    id("org.jetbrains.kotlin.jvm") apply false
+}
+
+abstract class CustomResGenerator : DefaultTask() {
+    @get:OutputDirectory
+    abstract val outputFile: DirectoryProperty
+
+    @TaskAction
+    fun doGenerate() {
+        val dir = outputFile.get().asFile
+        dir.mkdirs()
+        dir.resolve("myres.txt").writeText("Banana!")
+    }
+}
+
+val customResGenerator = tasks.register<CustomResGenerator>("customResGenerator") {
+    outputFile.value(project.layout.buildDirectory.dir("custom-res"))
+}
+
+sourceSets.getByName("main").resources.srcDir(customResGenerator)
+
+plugins.apply("org.jetbrains.kotlin.jvm")

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/AbstractKotlinPlugin.kt

@@ -26,6 +26,8 @@ import org.jetbrains.kotlin.gradle.plugin.internal.JavaSourceSetsAccessor
 import org.jetbrains.kotlin.gradle.plugin.internal.MavenPluginConfigurator
 import org.jetbrains.kotlin.gradle.plugin.internal.compatibilityConventionRegistrar
 import org.jetbrains.kotlin.gradle.plugin.mpp.*
+import org.jetbrains.kotlin.gradle.plugin.sources.DefaultKotlinSourceSet
+import org.jetbrains.kotlin.gradle.plugin.sources.KotlinSourceSetFactory
 import org.jetbrains.kotlin.gradle.tasks.InspectClassesForMultiModuleIC
 import org.jetbrains.kotlin.gradle.tasks.KotlinTasksProvider
 import org.jetbrains.kotlin.gradle.tasks.locateTask
@@ -180,19 +182,24 @@ internal abstract class AbstractKotlinPlugin(
                     val kotlinSourceSet = project.kotlinExtension.sourceSets.maybeCreate(kotlinCompilation.name)
                     kotlinSourceSet.kotlin.source(javaSourceSet.java)
 
-                    // Registering resources from KotlinSourceSet as Java SourceSet resources.
+                    // Registering resources from JavaSourceSet as KotlinSourceSet resources.
                     // In the case of KotlinPlugin Java Sources set will create ProcessResources task to process all resources into output
                     // 'kotlinSourceSet.resources' should contain Java SourceSet default resource directories,
-                    // and to avoid duplication error, we are replacing the already configured default one.
+                    // and to avoid duplication error, we are replacing the already created default one.
+                    with(kotlinSourceSet as DefaultKotlinSourceSet) {
+                        val defaultResources = actualResources
+                        actualResources = javaSourceSet.resources
+                        // Filtering out default resource directory to avoid duplicates error
+                        val defaultResourcesDir = KotlinSourceSetFactory.defaultSourceFolder(
+                            project,
+                            javaSourceSet.name,
+                            javaSourceSet.resources.name
+                        )
+                        resources.srcDir(defaultResources.sourceDirectories.filter {
+                            !it.startsWith(defaultResourcesDir)
+                        })
+                    }
 
-                    // If KGP was applied with delay, it is possible that 'javaSourceSet.resources' may already have some additional
-                    // configuration. So we are syncing it into 'kotlinSourceSet.resources'.
-                    kotlinSourceSet.resources.srcDirs(javaSourceSet.resources.sourceDirectories.files)
-                    javaSourceSet.resources.setSrcDirs(
-                        listOf {
-                            kotlinSourceSet.resources.sourceDirectories
-                        }
-                    )
                     @Suppress("DEPRECATION")
                     kotlinCompilation.addSourceSet(kotlinSourceSet)
                     project.compatibilityConventionRegistrar.addConvention(javaSourceSet, kotlinSourceSetDslName, kotlinSourceSet)

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/DefaultKotlinSourceSet.kt

@@ -73,7 +73,9 @@ abstract class DefaultKotlinSourceSet @Inject constructor(
 
     override val languageSettings: LanguageSettingsBuilder = DefaultLanguageSettingsBuilder(project)
 
-    override val resources: SourceDirectorySet = createDefaultSourceDirectorySet(project, "$name resources")
+    internal var actualResources: SourceDirectorySet = createDefaultSourceDirectorySet(project, "$name resources")
+
+    override val resources: SourceDirectorySet get() = actualResources
 
     override fun kotlin(configure: SourceDirectorySet.() -> Unit): SourceDirectorySet = kotlin.apply {
         configure(this)

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/KotlinSourceSetFactory.kt

@@ -36,7 +36,7 @@ internal abstract class KotlinSourceSetFactory<T : KotlinSourceSet> internal con
     }
 
     protected open fun setUpSourceSetDefaults(sourceSet: T) {
-        sourceSet.kotlin.srcDir(defaultSourceFolder(project, sourceSet.name, "kotlin"))
+        sourceSet.kotlin.srcDir(defaultSourceFolder(project, sourceSet.name, SOURCE_SET_TYPE_KOTLIN))
         defineSourceSetConfigurations(project, sourceSet)
     }
 
@@ -68,6 +68,9 @@ internal abstract class KotlinSourceSetFactory<T : KotlinSourceSet> internal con
         fun defaultSourceFolder(project: Project, sourceSetName: String, type: String): File {
             return project.file("src/$sourceSetName/$type")
         }
+
+        internal const val SOURCE_SET_TYPE_RESOURCES = "resources"
+        internal const val SOURCE_SET_TYPE_KOTLIN = "kotlin"
     }
 }
 
@@ -81,7 +84,7 @@ internal class DefaultKotlinSourceSetFactory(
 
     override fun setUpSourceSetDefaults(sourceSet: DefaultKotlinSourceSet) {
         super.setUpSourceSetDefaults(sourceSet)
-        sourceSet.resources.srcDir(defaultSourceFolder(project, sourceSet.name, "resources"))
+        sourceSet.resources.srcDir(defaultSourceFolder(project, sourceSet.name, SOURCE_SET_TYPE_RESOURCES))
 
         val dependencyConfigurationWithMetadata = with(sourceSet) {
             @Suppress("DEPRECATION")