Make KSP compatible with Gradle's isolated projects

WIP

Bug: https://issuetracker.google.com/issues/361415637
Test: AndroidIT.kt

Author: scott-pollom

gradle-plugin/src/main/kotlin/com/google/devtools/ksp/gradle/KspAATask.kt

@@ -167,21 +167,9 @@ abstract class KspAATask @Inject constructor(
                     cfg.moduleName.value(moduleName)
                     val kotlinOutputDir = KspGradleSubplugin.getKspKotlinOutputDir(project, sourceSetName, target)
                     val javaOutputDir = KspGradleSubplugin.getKspJavaOutputDir(project, sourceSetName, target)
-                    val filteredTasks =
-                        kspExtension.excludedSources.buildDependencies.getDependencies(null).map { it.name }
                     kotlinCompilation.allKotlinSourceSetsObservable.forAll { sourceSet ->
-                        val filtered = sourceSet.kotlin.srcDirs.filter {
-                            !kotlinOutputDir.isParentOf(it) && !javaOutputDir.isParentOf(it) &&
-                                it !in kspExtension.excludedSources
-                        }.map {
-                            // @SkipWhenEmpty doesn't work well with File.
-                            project.objects.fileTree().from(it)
-                        }
-                        cfg.sourceRoots.from(filtered)
-                        cfg.javaSourceRoots.from(filtered)
-                        kspAATask.dependsOn(
-                            sourceSet.kotlin.nonSelfDeps(kspTaskName).filter { it.name !in filteredTasks }
-                        )
+                        cfg.sourceRoots.from(sourceSet.kotlin.sourceDirectories)
+                        cfg.javaSourceRoots.from(sourceSet.kotlin.sourceDirectories)
                     }
                     if (kotlinCompilation is KotlinCommonCompilation) {
                         cfg.commonSourceRoots.from(kotlinCompilation.defaultSourceSet.kotlin)

gradle-plugin/src/main/kotlin/com/google/devtools/ksp/gradle/KspExtension.kt

@@ -43,6 +43,7 @@ abstract class KspExtension @Inject constructor(project: Project) {
 
     // Specify sources that should be excluded from KSP.
     // If you have a task that generates sources, you can call `ksp.excludedSources.from(task)`.
+    // TODO - Deprecate and then remove this DSL?
     abstract val excludedSources: ConfigurableFileCollection
 
     open val arguments: Map<String, String> get() = apOptions.get()

gradle-plugin/src/main/kotlin/com/google/devtools/ksp/gradle/KspSubplugin.kt

@@ -360,16 +360,8 @@ class KspGradleSubplugin @Inject internal constructor(private val registry: Tool
                     )
                 }
             } else {
-                val filteredTasks =
-                    kspExtension.excludedSources.buildDependencies.getDependencies(null).map { it.name }
                 kotlinCompilation.allKotlinSourceSetsObservable.forAll { sourceSet ->
-                    kspTask.setSource(
-                        sourceSet.kotlin.srcDirs.filter {
-                            !kotlinOutputDir.isParentOf(it) && !javaOutputDir.isParentOf(it) &&
-                                it !in kspExtension.excludedSources
-                        }
-                    )
-                    kspTask.dependsOn(sourceSet.kotlin.nonSelfDeps(kspTaskName).filter { it.name !in filteredTasks })
+                    kspTask.setSource(sourceSet.kotlin.sourceDirectories)
                 }
             }
 
@@ -603,13 +595,7 @@ class KspGradleSubplugin @Inject internal constructor(private val registry: Tool
             project.files(kotlinOutputDir).builtBy(kspTaskProvider),
             project.files(javaOutputDir).builtBy(kspTaskProvider),
         )
-        if (kotlinCompilation is KotlinCommonCompilation) {
-            // Do not add generated sources to common source sets.
-            // They will be observed by downstreams and violate current build scheme.
-            kotlinCompileProvider.configure { it.source(*generatedSources) }
-        } else {
-            kotlinCompilation.defaultSourceSet.kotlin.srcDirs(*generatedSources)
-        }
+        kotlinCompileProvider.configure { it.source(*generatedSources) }
 
         kotlinCompileProvider.configure { kotlinCompile ->
             when (kotlinCompile) {

integration-tests/src/test/kotlin/com/google/devtools/ksp/test/AndroidIT.kt

@@ -21,7 +21,12 @@ class AndroidIT(useKSP2: Boolean) {
 
         // Disabling configuration cache. See https://github.com/google/ksp/issues/299 for details
         gradleRunner.withArguments(
-            "clean", "build", "minifyReleaseWithR8", "--configuration-cache-problems=warn", "--info", "--stacktrace"
+            "clean",
+            "build",
+            "minifyReleaseWithR8",
+            "--info",
+            "--stacktrace",
+            "-Dorg.gradle.unsafe.isolated-projects=true"
         ).build().let { result ->
             Assert.assertEquals(TaskOutcome.SUCCESS, result.task(":workload:build")?.outcome)
             val mergedConfiguration = File(project.root, "workload/build/outputs/mapping/release/configuration.txt")

integration-tests/src/test/resources/playground-android/build.gradle.kts

@@ -8,13 +8,3 @@ buildscript {
         google()
     }
 }
-
-allprojects {
-    val testRepo: String by project
-    repositories {
-        maven(testRepo)
-        mavenCentral()
-        maven("https://maven.pkg.jetbrains.space/kotlin/p/kotlin/bootstrap/")
-        google()
-    }
-}

integration-tests/src/test/resources/playground-android/test-processor/build.gradle.kts

@@ -12,6 +12,7 @@ repositories {
     maven(testRepo)
     mavenCentral()
     maven("https://maven.pkg.jetbrains.space/kotlin/p/kotlin/bootstrap/")
+    google()
 }
 
 dependencies {

integration-tests/src/test/resources/playground-android/workload/build.gradle.kts

@@ -13,6 +13,7 @@ repositories {
     maven(testRepo)
     mavenCentral()
     maven("https://maven.pkg.jetbrains.space/kotlin/p/kotlin/bootstrap/")
+    google()
 }
 
 dependencies {