Create a spotlessSetup plugin, and repurpose RegisterDependenciesTask so that it stores a value which can be injected into the SpotlessTaskService on every build.

Author: nedtwigg

plugin-gradle/build.gradle

@@ -45,6 +45,12 @@ gradlePlugin {
 			displayName = 'Spotless formatting plugin'
 			description = project.description
 		}
+		spotlessSetupPlugin {
+			id = 'com.diffplug.spotless-setup'
+			implementationClass = 'com.diffplug.gradle.spotless.SpotlessSetupPlugin'
+			displayName = 'Spotless formatting plugin setup'
+			description = project.description
+		}
 		spotlessPluginLegacy {
 			id = 'com.diffplug.gradle.spotless'
 			implementationClass = 'com.diffplug.gradle.spotless.SpotlessPluginRedirect'
@@ -78,6 +84,9 @@ if (version.endsWith('-SNAPSHOT')) {
 			'clang-format'
 		]
 		plugins {
+			spotlessSetupPlugin {
+				id = 'com.diffplug.spotless-setup'
+			}
 			spotlessPlugin {
 				id = 'com.diffplug.spotless'
 			}

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

@@ -15,22 +15,17 @@
  */
 package com.diffplug.gradle.spotless;
 
-import java.io.File;
-import java.io.IOException;
-import java.nio.charset.StandardCharsets;
-
 import javax.inject.Inject;
 
 import org.gradle.api.DefaultTask;
 import org.gradle.api.provider.Property;
 import org.gradle.api.services.BuildServiceRegistry;
+import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.Internal;
-import org.gradle.api.tasks.OutputFile;
 import org.gradle.api.tasks.TaskAction;
 import org.gradle.build.event.BuildEventsListenerRegistry;
 
 import com.diffplug.common.base.Preconditions;
-import com.diffplug.common.io.Files;
 
 /**
  * NOT AN END-USER TASK, DO NOT USE FOR ANYTHING!
@@ -59,26 +54,24 @@ void hookSubprojectTask(SpotlessTask task) {
 		task.dependsOn(this);
 	}
 
-	File unitOutput;
-
-	@OutputFile
-	public File getUnitOutput() {
-		return unitOutput;
-	}
-
 	void setup() {
 		Preconditions.checkArgument(getProject().getRootProject() == getProject(), "Can only be used on the root project");
-		unitOutput = new File(getProject().getBuildDir(), "tmp/spotless-register-dependencies");
 
 		BuildServiceRegistry buildServices = getProject().getGradle().getSharedServices();
 		getTaskService().set(buildServices.registerIfAbsent("SpotlessTaskService", SpotlessTaskService.class, spec -> {}));
 		getBuildEventsListenerRegistry().onTaskCompletion(getTaskService());
 	}
 
+	boolean enableConfigCacheDaemonLocal;
+
+	@Input
+	public boolean getEnableConfigCacheDaemonLocal() {
+		return enableConfigCacheDaemonLocal;
+	}
+
 	@TaskAction
-	public void trivialFunction() throws IOException {
-		Files.createParentDirs(unitOutput);
-		Files.write(Integer.toString(1), unitOutput, StandardCharsets.UTF_8);
+	public void trivialFunction() {
+		getTaskService().get().registerDependenciesTask(this);
 	}
 
 	@Internal

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

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2021 DiffPlug
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.diffplug.gradle.spotless;
+
+import org.gradle.api.Project;
+import org.gradle.api.tasks.TaskProvider;
+
+public class SpotlessSetup {
+	static final String NAME = "spotlessSetup";
+
+	private final TaskProvider<RegisterDependenciesTask> task;
+
+	public SpotlessSetup(Project project) {
+		task = (TaskProvider<RegisterDependenciesTask>) (Object) project.getTasks().named(RegisterDependenciesTask.TASK_NAME);
+	}
+
+	public boolean isEnableConfigCacheDaemonLocal() {
+		return task.get().getEnableConfigCacheDaemonLocal();
+	}
+
+	public boolean setEnableConfigCacheDaemonLocal(boolean enabled) {
+		return task.get().enableConfigCacheDaemonLocal = enabled;
+	}
+}

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

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2021 DiffPlug
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.diffplug.gradle.spotless;
+
+import org.gradle.api.Plugin;
+import org.gradle.api.Project;
+
+import com.diffplug.common.base.Preconditions;
+
+public class SpotlessSetupPlugin implements Plugin<Project> {
+	@Override
+	public void apply(Project rootProject) {
+		Preconditions.checkArgument(rootProject.getProject() == rootProject.getRootProject(), "com.diffplug.spotless-setup must be applied to only the root project");
+		rootProject.getPlugins().apply(SpotlessPlugin.class);
+		rootProject.getExtensions().create(SpotlessSetup.NAME, SpotlessSetup.class, rootProject);
+	}
+}

plugin-gradle/src/test/java/com/diffplug/gradle/spotless/UpToDateTest.java

@@ -88,8 +88,8 @@ void testPathologicalCase() throws IOException {
 		// the format task is UP-TO-DATE (same inputs), but the apply tasks will run again
 		pauseForFilesystem();
 		BuildResult buildResult = gradleRunner().withArguments("spotlessApply").build();
-		Assertions.assertThat(buildResult.taskPaths(TaskOutcome.UP_TO_DATE)).containsExactly(":spotlessInternalRegisterDependencies", ":spotlessMisc");
-		Assertions.assertThat(buildResult.taskPaths(TaskOutcome.SUCCESS)).containsExactly(":spotlessMiscApply", ":spotlessApply");
+		Assertions.assertThat(buildResult.taskPaths(TaskOutcome.UP_TO_DATE)).containsExactly(":spotlessMisc");
+		Assertions.assertThat(buildResult.taskPaths(TaskOutcome.SUCCESS)).containsExactly(":spotlessInternalRegisterDependencies", ":spotlessMiscApply", ":spotlessApply");
 		assertFile("README.md").hasContent("abc");
 
 		// and it'll take two more runs to get to fully UP-TO-DATE