Fix CheckTask's up-to-date behaviour

Previously, CheckTask instances would never be up-to-date as the
task had an action but did not declare any outputs. As the task does
not produce any output, this commit fixes its up-to-date checks by
marking its outputs as always being up-to-date.

Closes gh-116

Author: wilkinsona

spring-javaformat-gradle/spring-javaformat-gradle-plugin/src/main/java/io/spring/javaformat/gradle/CheckTask.java

@@ -43,6 +43,10 @@ public class CheckTask extends FormatterTask {
 	 */
 	public static final String DESCRIPTION = "Run Spring Java formatting checks";
 
+	public CheckTask() {
+		getOutputs().upToDateWhen((task) -> true);
+	}
+
 	@TaskAction
 	public void checkFormatting() throws IOException, InterruptedException {
 		List<File> problems = formatFiles().filter(FileEdit::hasEdits).map(FileEdit::getFile)

spring-javaformat-gradle/spring-javaformat-gradle-plugin/src/test/java/io/spring/javaformat/gradle/CheckTaskTests.java

@@ -43,10 +43,28 @@ public void checkOk() throws IOException {
 		assertThat(result.task(":checkFormatMain").getOutcome()).isEqualTo(TaskOutcome.SUCCESS);
 	}
 
+	@Test
+	public void whenFirstInvocationSucceedsThenSecondInvocationIsUpToDate() throws IOException {
+		GradleBuild gradleBuild = this.gradleBuild.source("src/test/resources/check-ok");
+		BuildResult result = gradleBuild.build("check");
+		assertThat(result.task(":checkFormatMain").getOutcome()).isEqualTo(TaskOutcome.SUCCESS);
+		result = gradleBuild.build("check");
+		assertThat(result.task(":checkFormatMain").getOutcome()).isEqualTo(TaskOutcome.UP_TO_DATE);
+	}
+
 	@Test
 	public void checkBad() throws IOException {
 		BuildResult result = this.gradleBuild.source("src/test/resources/check-bad").buildAndFail("check");
 		assertThat(result.task(":checkFormatMain").getOutcome()).isEqualTo(TaskOutcome.FAILED);
 	}
 
+	@Test
+	public void whenFirstInvocationFailsThenSecondInvocationFails() throws IOException {
+		GradleBuild gradleBuild = this.gradleBuild.source("src/test/resources/check-bad");
+		BuildResult result = gradleBuild.buildAndFail("check");
+		assertThat(result.task(":checkFormatMain").getOutcome()).isEqualTo(TaskOutcome.FAILED);
+		result = gradleBuild.buildAndFail("check");
+		assertThat(result.task(":checkFormatMain").getOutcome()).isEqualTo(TaskOutcome.FAILED);
+	}
+
 }

spring-javaformat-gradle/spring-javaformat-gradle-plugin/src/test/java/io/spring/javaformat/gradle/testkit/GradleBuild.java

@@ -154,7 +154,9 @@ private void copyFolder(Path source, Path target) throws IOException {
 				try {
 					Path relative = source.relativize(child);
 					Path destination = target.resolve(relative);
-					Files.copy(child, destination, StandardCopyOption.REPLACE_EXISTING);
+					if (!destination.toFile().isDirectory()) {
+						Files.copy(child, destination, StandardCopyOption.REPLACE_EXISTING);
+					}
 				}
 				catch (Exception ex) {
 					throw new IllegalStateException(ex);