Workaround to preserve instanceof BuildServiceProvider (blech, see #1260 for my complaint).

Author: nedtwigg

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/RegisterDependenciesTask.java

@@ -24,7 +24,7 @@
 import javax.inject.Inject;
 
 import org.gradle.api.DefaultTask;
-import org.gradle.api.provider.Property;
+import org.gradle.api.provider.Provider;
 import org.gradle.api.services.BuildServiceRegistry;
 import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.Internal;
@@ -63,9 +63,9 @@ void setup() {
 		Preconditions.checkArgument(getProject().getRootProject() == getProject(), "Can only be used on the root project");
 		String compositeBuildSuffix = getName().substring(TASK_NAME.length()); // see https://github.com/diffplug/spotless/pull/1001
 		BuildServiceRegistry buildServices = getProject().getGradle().getSharedServices();
-		getTaskService().set(buildServices.registerIfAbsent("SpotlessTaskService" + compositeBuildSuffix, SpotlessTaskService.class, spec -> {}));
-		usesService(getTaskService());
-		getBuildEventsListenerRegistry().onTaskCompletion(getTaskService());
+		taskService = buildServices.registerIfAbsent("SpotlessTaskService" + compositeBuildSuffix, SpotlessTaskService.class, spec -> {});
+		usesService(taskService);
+		getBuildEventsListenerRegistry().onTaskCompletion(taskService);
 		unitOutput = new File(getProject().getBuildDir(), "tmp/spotless-register-dependencies");
 	}
 
@@ -89,8 +89,13 @@ public void trivialFunction() throws IOException {
 		Files.write(Integer.toString(1), unitOutput, StandardCharsets.UTF_8);
 	}
 
+	// this field is stupid, but we need it, see https://github.com/diffplug/spotless/issues/1260
+	private Provider<SpotlessTaskService> taskService;
+
 	@Internal
-	abstract Property<SpotlessTaskService> getTaskService();
+	public Provider<SpotlessTaskService> getTaskService() {
+		return taskService;
+	}
 
 	@Inject
 	protected abstract BuildEventsListenerRegistry getBuildEventsListenerRegistry();

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessTaskImpl.java

@@ -46,11 +46,20 @@ public abstract class SpotlessTaskImpl extends SpotlessTask {
 	abstract DirectoryProperty getProjectDir();
 
 	void init(Provider<SpotlessTaskService> service) {
+		taskServiceProvider = service;
 		usesService(service);
 		getTaskService().set(service);
 		getProjectDir().set(getProject().getProjectDir());
 	}
 
+	// this field is stupid, but we need it, see https://github.com/diffplug/spotless/issues/1260
+	private transient Provider<SpotlessTaskService> taskServiceProvider;
+
+	@Internal
+	Provider<SpotlessTaskService> getTaskServiceProvider() {
+		return taskServiceProvider;
+	}
+
 	@Inject
 	protected abstract FileSystemOperations getFs();
 

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessTaskService.java

@@ -105,7 +105,7 @@ static abstract class ClientTask extends DefaultTask {
 		protected abstract ObjectFactory getConfigCacheWorkaround();
 
 		void init(SpotlessTaskImpl impl) {
-			usesService(impl.getTaskService());
+			usesService(impl.getTaskServiceProvider());
 			getSpotlessOutDirectory().set(impl.getOutputDirectory());
 			getTaskService().set(impl.getTaskService());
 			getProjectDir().set(impl.getProjectDir());