Enable :gradle-plugin strict validation

Enable Gradle Plugin types strict validation by the :gradle-plugin:validatePlugins task. The task now applies more rules for plugin types.

Add missing mandatory cacheability annotations on SpotlessTask, SpotlessApply, SpotlessCheck and SpotlessDiagnoseTask.

Author: eskatos

plugin-gradle/build.gradle

@@ -33,6 +33,9 @@ apply from: rootProject.file('gradle/special-tests.gradle')
 tasks.withType(Test).configureEach {
 	testLogging.showStandardStreams = true
 }
+tasks.validatePlugins {
+	enableStricterValidation = true
+}
 
 //////////////////////////
 // GRADLE PLUGIN PORTAL //

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2024 DiffPlug
+ * Copyright 2016-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,7 +25,9 @@
 import org.gradle.api.file.FileVisitDetails;
 import org.gradle.api.file.FileVisitor;
 import org.gradle.api.tasks.TaskAction;
+import org.gradle.work.DisableCachingByDefault;
 
+@DisableCachingByDefault(because = "not worth caching")
 public abstract class SpotlessApply extends SpotlessTaskService.ClientTask {
 	@TaskAction
 	public void performAction() {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2024 DiffPlug
+ * Copyright 2016-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -32,12 +32,14 @@
 import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.Internal;
 import org.gradle.api.tasks.TaskAction;
+import org.gradle.work.DisableCachingByDefault;
 import org.jetbrains.annotations.NotNull;
 
 import com.diffplug.spotless.FileSignature;
 import com.diffplug.spotless.ThrowingEx;
 import com.diffplug.spotless.extra.integration.DiffMessageFormatter;
 
+@DisableCachingByDefault(because = "not worth caching")
 public abstract class SpotlessCheck extends SpotlessTaskService.ClientTask {
 	@Internal
 	public abstract Property<String> getEncoding();

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2023 DiffPlug
+ * Copyright 2016-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,12 +25,14 @@
 import org.gradle.api.DefaultTask;
 import org.gradle.api.tasks.Internal;
 import org.gradle.api.tasks.TaskAction;
+import org.gradle.api.tasks.UntrackedTask;
 
 import com.diffplug.spotless.Formatter;
 import com.diffplug.spotless.PaddedCell;
 
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 
+@UntrackedTask(because = "undeclared inputs/outputs")
 public class SpotlessDiagnoseTask extends DefaultTask {
 	SpotlessTask source;
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2024 DiffPlug
+ * Copyright 2020-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,6 +34,7 @@
 import org.gradle.api.tasks.OutputDirectory;
 import org.gradle.api.tasks.PathSensitive;
 import org.gradle.api.tasks.PathSensitivity;
+import org.gradle.work.DisableCachingByDefault;
 import org.gradle.work.Incremental;
 
 import com.diffplug.spotless.ConfigurationCacheHackList;
@@ -43,6 +44,7 @@
 import com.diffplug.spotless.LintSuppression;
 import com.diffplug.spotless.extra.GitRatchet;
 
+@DisableCachingByDefault(because = "abstract definition")
 public abstract class SpotlessTask extends DefaultTask {
 	@Internal
 	abstract Property<SpotlessTaskService> getTaskService();