Prevent gradle from skipping the IDE hook task due to cached results

plugin-gradle/CHANGES.md

@@ -4,6 +4,9 @@ We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (
 
 ## [Unreleased]
 
+### Fixed
+- Prevent build caches from interfering when executing under the `-PspotlessIdeHook` mode. ([#2365](https://github.com/diffplug/spotless/issues/2365))
+
 ## [8.6.0] - 2026-05-27
 ### Added
 - Add `cacheDirectory(...)` to `eclipse()`, `eclipseCdt()`, and `greclipse()`; the default P2 cache is `$GRADLE_USER_HOME/caches/p2-data`. ([#2944](https://github.com/diffplug/spotless/pull/2944))

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

@@ -66,6 +66,13 @@ protected void createFormatTasks(String name, FormatExtension formatExtension) {
 			task.getIdeHookState().set(ideHook);
 			// clean removes the SpotlessCache, so we have to run after clean
 			task.mustRunAfter(BasePlugin.CLEAN_TASK_NAME);
+			if (ideHook.paths != null) {
+				// The IDE hook never writes to the declared outputs so Gradle's UP-TO-DATE check would incorrectly
+				// skip the task when the user reverts a file or when useStdOut is active.
+				task.getOutputs().upToDateWhen(t -> false);
+				// also disable the build cache
+				task.getOutputs().cacheIf("IDE hook always reruns", t -> false);
+			}
 		});
 		project.afterEvaluate(unused -> spotlessTask.configure(task -> {
 			// now that the task is being configured, we execute our actions

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

@@ -119,6 +119,33 @@ void dirty(boolean configurationCache) throws IOException {
 		Assertions.assertThat(error).startsWith("IS DIRTY");
 	}
 
+	@ParameterizedTest
+	@MethodSource("configurationCacheProvider")
+	void dirtyCalledTwiceWithStdOut(boolean configurationCache) throws IOException {
+		// Make sure gradle doesn't cache the output of the first call, since it must be written to stdout again
+		runWith(configurationCache, "spotlessApply", "--quiet", "-PspotlessIdeHook=" + dirty.getAbsolutePath(), "-PspotlessIdeHookUseStdOut");
+		Assertions.assertThat(output).isEqualTo("abc");
+		Assertions.assertThat(error).startsWith("IS DIRTY");
+
+		runWith(configurationCache, "spotlessApply", "--quiet", "-PspotlessIdeHook=" + dirty.getAbsolutePath(), "-PspotlessIdeHookUseStdOut");
+		Assertions.assertThat(output).isEqualTo("abc");
+		Assertions.assertThat(error).startsWith("IS DIRTY");
+	}
+
+	@ParameterizedTest
+	@MethodSource("configurationCacheProvider")
+	void dirtyCalledTwiceAfterRevert(boolean configurationCache) throws IOException {
+		// Make sure Gradle doesn't skip writing to the file just because it was already dirty in the previous run
+		// - the content may have been reverted in between
+		runWith(configurationCache, "spotlessApply", "--quiet", "-PspotlessIdeHook=" + dirty.getAbsolutePath());
+		Assertions.assertThat(error).startsWith("IS DIRTY");
+
+		Files.write("ABC".getBytes(StandardCharsets.UTF_8), dirty);
+
+		runWith(configurationCache, "spotlessApply", "--quiet", "-PspotlessIdeHook=" + dirty.getAbsolutePath());
+		Assertions.assertThat(error).startsWith("IS DIRTY");
+	}
+
 	@ParameterizedTest
 	@MethodSource("configurationCacheProvider")
 	void clean(boolean configurationCache) throws IOException {