Fix and test no cache gen sources (#1183)

* Fix and test no cache gen sources

* Spotless

src/main/java/net/fabricmc/loom/task/GenerateSourcesTask.java

@@ -250,6 +250,8 @@ public void run() throws IOException {
 		}
 
 		if (!getUseCache().get()) {
+			getLogger().info("Not using decompile cache.");
+
 			try (var timer = new Timer("Decompiled sources")) {
 				runWithoutCache();
 			} catch (Exception e) {
@@ -340,49 +342,42 @@ private void runWithCache(Path cacheRoot) throws IOException {
 		final ClassLineNumbers existingLinenumbers = workRequest.lineNumbers();
 		final ClassLineNumbers lineNumbers = ClassLineNumbers.merge(existingLinenumbers, outputLineNumbers);
 
-		if (lineNumbers == null) {
-			getLogger().info("No line numbers to remap, skipping remapping");
-			return;
-		}
-
-		Path tempJar = Files.createTempFile("loom", "linenumber-remap.jar");
-		Files.delete(tempJar);
-
-		try (var timer = new Timer("Remap line numbers")) {
-			remapLineNumbers(lineNumbers, classesInputJar, tempJar);
-		}
-
-		Files.move(tempJar, classesOutputJar, StandardCopyOption.REPLACE_EXISTING);
+		applyLineNumbers(lineNumbers, classesInputJar, classesOutputJar);
 
 		try (var timer = new Timer("Prune cache")) {
 			decompileCache.prune();
 		}
 	}
 
 	private void runWithoutCache() throws IOException {
-		Path inputJar = getClassesInputJar().getSingleFile().toPath();
-		final Path outputJar = getSourcesOutputJar().get().getAsFile().toPath();
+		final Path classesInputJar = getClassesInputJar().getSingleFile().toPath();
+		final Path sourcesOutputJar = getSourcesOutputJar().get().getAsFile().toPath();
+		final Path classesOutputJar = getClassesOutputJar().getSingleFile().toPath();
 
-		// The final output sources jar
+		Path workClassesJar = classesInputJar;
 
 		if (getUnpickDefinitions().isPresent()) {
 			try (var timer = new Timer("Unpick")) {
-				inputJar = unpickJar(inputJar, null);
+				workClassesJar = unpickJar(workClassesJar, null);
 			}
 		}
 
 		ClassLineNumbers lineNumbers;
 
 		try (var timer = new Timer("Decompile")) {
-			lineNumbers = runDecompileJob(inputJar, outputJar, null);
+			lineNumbers = runDecompileJob(workClassesJar, sourcesOutputJar, null);
 		}
 
-		if (Files.notExists(outputJar)) {
+		if (Files.notExists(sourcesOutputJar)) {
 			throw new RuntimeException("Failed to decompile sources");
 		}
 
-		getLogger().info("Decompiled sources written to {}", outputJar);
+		getLogger().info("Decompiled sources written to {}", sourcesOutputJar);
+
+		applyLineNumbers(lineNumbers, classesInputJar, classesOutputJar);
+	}
 
+	private void applyLineNumbers(@Nullable ClassLineNumbers lineNumbers, Path classesInputJar, Path classesOutputJar) throws IOException {
 		if (lineNumbers == null) {
 			getLogger().info("No line numbers to remap, skipping remapping");
 			return;
@@ -392,10 +387,10 @@ private void runWithoutCache() throws IOException {
 		Files.delete(tempJar);
 
 		try (var timer = new Timer("Remap line numbers")) {
-			remapLineNumbers(lineNumbers, inputJar, tempJar);
+			remapLineNumbers(lineNumbers, classesInputJar, tempJar);
 		}
 
-		Files.move(tempJar, outputJar, StandardCopyOption.REPLACE_EXISTING);
+		Files.move(tempJar, classesOutputJar, StandardCopyOption.REPLACE_EXISTING);
 	}
 
 	private String getCacheKey() {

src/test/groovy/net/fabricmc/loom/test/integration/UnpickTest.groovy

@@ -37,17 +37,27 @@ import static org.gradle.testkit.runner.TaskOutcome.SUCCESS
 class UnpickTest extends Specification implements GradleProjectTestTrait {
 	static final String MAPPINGS = "21w13a-net.fabricmc.yarn.21w13a.21w13a+build.30-v2"
 
-	def "unpick decompile"() {
+	def "unpick decompile #version #useCache"() {
 		setup:
 		def gradle = gradleProject(project: "unpick", version: version)
 
 		when:
-		def result = gradle.run(task: "genSources")
+		def result = gradle.run(tasks: useCache ? [
+			"genSourcesWithVineflower",
+			"--info"
+		] : [
+			"genSourcesWithVineflower",
+			"--no-use-cache",
+			"--info"
+		])
 		then:
-		result.task(":genSources").outcome == SUCCESS
+		result.task(":genSourcesWithVineflower").outcome == SUCCESS
 		getClassSource(gradle, "net/minecraft/block/CakeBlock.java").contains("Block.DEFAULT_SET_BLOCK_STATE_FLAG")
+		result.output.contains(useCache ? "Using decompile cache." : "Not using decompile cache.")
+
 		where:
 		version << STANDARD_TEST_VERSIONS
+		useCache << [true, false]
 	}
 
 	def "unpick build"() {