[prone] Add ConstantNaming

gradle/error-prone.gradle

@@ -19,11 +19,16 @@ dependencies {
 tasks.withType(JavaCompile).configureEach {
 	options.errorprone {
 		disableAllChecks = true // consider removal to avoid error prone error´s, following convention over configuration.
-		error('RedundantStringConversion')
+		error(
+				'ConstantNaming',
+				'RedundantStringConversion',
+				)
 		if (!getenv().containsKey('CI') && getenv('IN_PLACE')?.toBoolean()) {
 			errorproneArgs.addAll(
 					'-XepPatchLocation:IN_PLACE',
-					'-XepPatchChecks:RedundantStringConversion'
+					'-XepPatchChecks:' +
+					'ConstantNaming,' +
+					'RedundantStringConversion,'
 					)
 		}
 	}

lib/src/compatKtLint0Dot49Dot0/java/com/diffplug/spotless/glue/ktlint/compat/KtLintCompat0Dot49Dot0Adapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 DiffPlug
+ * Copyright 2023-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -55,7 +55,7 @@
 
 public class KtLintCompat0Dot49Dot0Adapter implements KtLintCompatAdapter {
 
-	private static final Logger logger = LoggerFactory.getLogger(KtLintCompat0Dot49Dot0Adapter.class);
+	private static final Logger LOGGER = LoggerFactory.getLogger(KtLintCompat0Dot49Dot0Adapter.class);
 
 	private static final List<EditorConfigProperty<?>> DEFAULT_EDITOR_CONFIG_PROPERTIES;
 

lib/src/compatKtLint0Dot50Dot0/java/com/diffplug/spotless/glue/ktlint/compat/KtLintCompat0Dot50Dot0Adapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 DiffPlug
+ * Copyright 2023-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -55,7 +55,7 @@
 
 public class KtLintCompat0Dot50Dot0Adapter implements KtLintCompatAdapter {
 
-	private static final Logger logger = LoggerFactory.getLogger(KtLintCompat0Dot50Dot0Adapter.class);
+	private static final Logger LOGGER = LoggerFactory.getLogger(KtLintCompat0Dot50Dot0Adapter.class);
 
 	private static final List<EditorConfigProperty<?>> DEFAULT_EDITOR_CONFIG_PROPERTIES;
 

lib/src/compatKtLint1Dot0Dot0/java/com/diffplug/spotless/glue/ktlint/compat/KtLintCompat1Dot0Dot0Adapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 DiffPlug
+ * Copyright 2023-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -54,7 +54,7 @@
 
 public class KtLintCompat1Dot0Dot0Adapter implements KtLintCompatAdapter {
 
-	private static final Logger logger = LoggerFactory.getLogger(KtLintCompat1Dot0Dot0Adapter.class);
+	private static final Logger LOGGER = LoggerFactory.getLogger(KtLintCompat1Dot0Dot0Adapter.class);
 
 	private static final List<EditorConfigProperty<?>> DEFAULT_EDITOR_CONFIG_PROPERTIES;
 

lib/src/main/java/com/diffplug/spotless/DirtyState.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022-2024 DiffPlug
+ * Copyright 2022-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,19 +31,18 @@
  * then you can call {@link #writeCanonicalTo(OutputStream)} to get the canonical form of the given file.
  */
 public class DirtyState {
-	@Nullable
-	private final byte[] canonicalBytes;
+	@Nullable private final byte[] canonicalBytes;
 
 	DirtyState(@Nullable byte[] canonicalBytes) {
 		this.canonicalBytes = canonicalBytes;
 	}
 
 	public boolean isClean() {
-		return this == isClean;
+		return this == IS_CLEAN;
 	}
 
 	public boolean didNotConverge() {
-		return this == didNotConverge;
+		return this == DID_NOT_CONVERGE;
 	}
 
 	byte[] canonicalBytes() {
@@ -63,11 +62,11 @@ public void writeCanonicalTo(OutputStream out) throws IOException {
 
 	/** Returns the DirtyState which corresponds to {@code isClean()}. */
 	public static DirtyState clean() {
-		return isClean;
+		return IS_CLEAN;
 	}
 
-	static final DirtyState didNotConverge = new DirtyState(null);
-	static final DirtyState isClean = new DirtyState(null);
+	static final DirtyState DID_NOT_CONVERGE = new DirtyState(null);
+	static final DirtyState IS_CLEAN = new DirtyState(null);
 
 	public static DirtyState of(Formatter formatter, File file) throws IOException {
 		return of(formatter, file, Files.readAllBytes(file.toPath()));
@@ -101,7 +100,7 @@ static DirtyState of(Formatter formatter, File file, byte[] rawBytes, String raw
 		// if F(input) == input, then the formatter is well-behaving and the input is clean
 		byte[] formattedBytes = formatted.getBytes(formatter.getEncoding());
 		if (Arrays.equals(rawBytes, formattedBytes)) {
-			return isClean;
+			return IS_CLEAN;
 		}
 
 		// F(input) != input, so we'll do a padded check
@@ -113,7 +112,7 @@ static DirtyState of(Formatter formatter, File file, byte[] rawBytes, String raw
 
 		PaddedCell cell = PaddedCell.check(formatter, file, rawUnix, exceptionPerStep);
 		if (!cell.isResolvable()) {
-			return didNotConverge;
+			return DID_NOT_CONVERGE;
 		}
 
 		// get the canonical bytes
@@ -124,7 +123,7 @@ static DirtyState of(Formatter formatter, File file, byte[] rawBytes, String raw
 			// and write them to disk if needed
 			return new DirtyState(canonicalBytes);
 		} else {
-			return isClean;
+			return IS_CLEAN;
 		}
 	}
 }

lib/src/main/java/com/diffplug/spotless/FileSignature.java

@@ -93,7 +93,7 @@ private FileSignature(final List<File> files) throws IOException {
 
 		int i = 0;
 		for (File file : this.files) {
-			signatures[i] = cache.sign(file);
+			signatures[i] = CACHE.sign(file);
 			++i;
 		}
 	}
@@ -146,11 +146,11 @@ public File getOnlyFile() {
 		}
 	}
 
-	private static final boolean machineIsWin = System.getProperty("os.name").toLowerCase(Locale.ROOT).contains("win");
+	private static final boolean MACHINE_IS_WIN = System.getProperty("os.name").toLowerCase(Locale.ROOT).contains("win");
 
 	/** Returns true if this JVM is running on a windows machine. */
 	public static boolean machineIsWin() {
-		return machineIsWin;
+		return MACHINE_IS_WIN;
 	}
 
 	/** Transforms a native path to a unix one. */
@@ -179,7 +179,7 @@ private static List<File> validateInputFiles(List<File> files) {
 	 * the jars which constitute any given formatter live in a central cache, but will be signed
 	 * over and over.  To save this I/O, we maintain a cache, invalidated by lastModified time.
 	 */
-	static final Cache cache = new Cache();
+	static final Cache CACHE = new Cache();
 
 	private static final class Cache {
 		Map<String, Sig> cache = new HashMap<>();

lib/src/main/java/com/diffplug/spotless/Formatter.java

@@ -143,13 +143,13 @@ static void legacyErrorBehavior(Formatter formatter, File file, ValuePerStep<Thr
 		for (int i = 0; i < formatter.getSteps().size(); i++) {
 			Throwable exception = exceptionPerStep.get(i);
 			if (exception != null && exception != LintState.formatStepCausedNoChange()) {
-				logger.error("Step '{}' found problem in '{}':\n{}", formatter.getSteps().get(i).getName(), file.getName(), exception.getMessage(), exception);
+				LOGGER.error("Step '{}' found problem in '{}':\n{}", formatter.getSteps().get(i).getName(), file.getName(), exception.getMessage(), exception);
 				throw ThrowingEx.asRuntimeRethrowError(exception);
 			}
 		}
 	}
 
-	private static final Logger logger = LoggerFactory.getLogger(Formatter.class);
+	private static final Logger LOGGER = LoggerFactory.getLogger(Formatter.class);
 
 	/**
 	 * Returns the result of calling all of the FormatterSteps, while also

lib/src/main/java/com/diffplug/spotless/JarState.java

@@ -45,15 +45,15 @@
  */
 public final class JarState implements Serializable {
 
-	private static final Logger logger = LoggerFactory.getLogger(JarState.class);
+	private static final Logger LOGGER = LoggerFactory.getLogger(JarState.class);
 
 	// Let the classloader be overridden for tools using different approaches to classloading
 	@Nullable private static ClassLoader forcedClassLoader;
 
 	/** Overrides the classloader used by all JarStates. */
 	public static void setForcedClassLoader(@Nullable ClassLoader forcedClassLoader) {
 		if (!Objects.equals(JarState.forcedClassLoader, forcedClassLoader)) {
-			logger.info("Overriding the forced classloader for JarState from {} to {}", JarState.forcedClassLoader, forcedClassLoader);
+			LOGGER.info("Overriding the forced classloader for JarState from {} to {}", JarState.forcedClassLoader, forcedClassLoader);
 		}
 		JarState.forcedClassLoader = forcedClassLoader;
 	}

lib/src/main/java/com/diffplug/spotless/LineEnding.java

@@ -84,7 +84,7 @@ public Policy createPolicy(File projectDir, Supplier<Iterable<File>> toFormat) {
 	/** Should use {@link #createPolicy(File, Supplier)} instead, but this will work iff its a path-independent LineEnding policy. */
 	public Policy createPolicy() {
 		switch (this) {
-		case PLATFORM_NATIVE:	return _platformNativePolicy;
+		case PLATFORM_NATIVE:	return _PLATFORM_NATIVE_POLICY;
 		case WINDOWS:			return WINDOWS_POLICY;
 		case UNIX:				return UNIX_POLICY;
 		case MAC_CLASSIC:		return MAC_CLASSIC_POLICY;
@@ -152,9 +152,9 @@ static String getEndingFor(Reader reader) throws IOException {
 	private static final Policy UNIX_POLICY = new ConstantLineEndingPolicy(UNIX.str());
     private static final Policy MAC_CLASSIC_POLICY = new ConstantLineEndingPolicy(MAC_CLASSIC.str());
     private static final Policy PRESERVE_POLICY = new PreserveLineEndingPolicy();
-	private static final String _platformNative = System.getProperty("line.separator");
-	private static final Policy _platformNativePolicy = new ConstantLineEndingPolicy(_platformNative);
-	private static final boolean nativeIsWin = _platformNative.equals(WINDOWS.str());
+	private static final String _PLATFORM_NATIVE = System.getProperty("line.separator");
+	private static final Policy _PLATFORM_NATIVE_POLICY = new ConstantLineEndingPolicy(_PLATFORM_NATIVE);
+	private static final boolean NATIVE_IS_WIN = _PLATFORM_NATIVE.equals(WINDOWS.str());
 
 	/**
 	 * @deprecated Using the system-native line endings to detect the windows operating system has turned out
@@ -164,13 +164,13 @@ static String getEndingFor(Reader reader) throws IOException {
 	 */
 	@Deprecated
 	public static boolean nativeIsWin() {
-		return nativeIsWin;
+		return NATIVE_IS_WIN;
 	}
 
 	/** Returns the standard line ending for this policy. */
 	public String str() {
 		switch (this) {
-		case PLATFORM_NATIVE:	return _platformNative;
+		case PLATFORM_NATIVE:	return _PLATFORM_NATIVE;
 		case WINDOWS:			return "\r\n";
 		case UNIX:				return "\n";
 		case MAC_CLASSIC:		return "\r";

lib/src/main/java/com/diffplug/spotless/LintState.java

@@ -197,10 +197,10 @@ public static LintState of(Formatter formatter, File file, byte[] rawBytes) {
 
 	/** Returns the DirtyState which corresponds to {@code isClean()}. */
 	public static LintState clean() {
-		return isClean;
+		return IS_CLEAN;
 	}
 
-	private static final LintState isClean = new LintState(DirtyState.clean(), null);
+	private static final LintState IS_CLEAN = new LintState(DirtyState.clean(), null);
 
 	static Throwable formatStepCausedNoChange() {
 		return FormatterCausedNoChange.INSTANCE;

lib/src/main/java/com/diffplug/spotless/SpotlessCache.java

@@ -76,17 +76,17 @@ synchronized ClassLoader classloader(Serializable key, JarState state) {
 	}
 
 	static SpotlessCache instance() {
-		return instance;
+		return INSTANCE;
 	}
 
 	/**
 	 * Closes all cached classloaders.
 	 */
 	private static void clear() {
 		List<URLClassLoader> toDelete;
-		synchronized (instance) {
-			toDelete = new ArrayList<>(instance.cache.values());
-			instance.cache.clear();
+		synchronized (INSTANCE) {
+			toDelete = new ArrayList<>(INSTANCE.cache.values());
+			INSTANCE.cache.clear();
 		}
 		for (URLClassLoader classLoader : toDelete) {
 			try {
@@ -104,7 +104,7 @@ private static void clear() {
 	 * If {@code key} is null, the clear will always happen (as though null != null).
 	 */
 	public static boolean clearOnce(@Nullable Object key) {
-		synchronized (instance) {
+		synchronized (INSTANCE) {
 			if (key == null) {
 				lastClear = null;
 			} else if (key.equals(lastClear)) {
@@ -117,5 +117,5 @@ public static boolean clearOnce(@Nullable Object key) {
 		return true;
 	}
 
-	private static final SpotlessCache instance = new SpotlessCache();
+	private static final SpotlessCache INSTANCE = new SpotlessCache();
 }

lib/src/main/java/com/diffplug/spotless/biome/BiomeExecutableDownloader.java

@@ -42,7 +42,7 @@
  * <a href="https://github.com/biomejs/biome">https://github.com/biomejs/biome</a>.
  */
 final class BiomeExecutableDownloader {
-	private static final Logger logger = LoggerFactory.getLogger(BiomeExecutableDownloader.class);
+	private static final Logger LOGGER = LoggerFactory.getLogger(BiomeExecutableDownloader.class);
 
 	/**
 	 * The checksum algorithm to use for checking the integrity of downloaded files.
@@ -106,7 +106,7 @@ public Path download(String version) throws IOException, InterruptedException {
 		if (executableDir != null) {
 			Files.createDirectories(executableDir);
 		}
-		logger.info("Attempting to download Biome from '{}' to '{}'", url, executablePath);
+		LOGGER.info("Attempting to download Biome from '{}' to '{}'", url, executablePath);
 		var request = HttpRequest.newBuilder(URI.create(url)).GET().build();
 		var handler = BodyHandlers.ofFile(executablePath, WRITE_OPTIONS);
 		var response = HttpClient.newBuilder().followRedirects(Redirect.NORMAL).build().send(request, handler);
@@ -118,7 +118,7 @@ public Path download(String version) throws IOException, InterruptedException {
 			throw new IOException("Failed to download file from " + url + ", file is empty or does not exist");
 		}
 		writeChecksumFile(downloadedFile, checksumPath);
-		logger.debug("Biome was downloaded successfully to '{}'", downloadedFile);
+		LOGGER.debug("Biome was downloaded successfully to '{}'", downloadedFile);
 		return downloadedFile;
 	}
 
@@ -142,13 +142,13 @@ public Path download(String version) throws IOException, InterruptedException {
 	 */
 	public Path ensureDownloaded(String version) throws IOException, InterruptedException {
 		var platform = Platform.guess();
-		logger.debug("Ensuring that Biome for platform '{}' is downloaded", platform);
+		LOGGER.debug("Ensuring that Biome for platform '{}' is downloaded", platform);
 		var existing = findDownloaded(version);
 		if (existing.isPresent()) {
-			logger.debug("Biome was already downloaded, using executable at '{}'", existing.orElseThrow());
+			LOGGER.debug("Biome was already downloaded, using executable at '{}'", existing.orElseThrow());
 			return existing.orElseThrow();
 		} else {
-			logger.debug("Biome was not yet downloaded, attempting to download executable");
+			LOGGER.debug("Biome was not yet downloaded, attempting to download executable");
 			return download(version);
 		}
 	}
@@ -169,7 +169,7 @@ public Path ensureDownloaded(String version) throws IOException, InterruptedExce
 	public Optional<Path> findDownloaded(String version) throws IOException {
 		var platform = Platform.guess();
 		var executablePath = getExecutablePath(version, platform);
-		logger.debug("Checking Biome executable at {}", executablePath);
+		LOGGER.debug("Checking Biome executable at {}", executablePath);
 		return checkFileWithChecksum(executablePath) ? Optional.ofNullable(executablePath) : Optional.empty();
 	}
 
@@ -183,26 +183,26 @@ public Optional<Path> findDownloaded(String version) throws IOException {
 	 */
 	private boolean checkFileWithChecksum(Path filePath) {
 		if (!Files.exists(filePath)) {
-			logger.debug("File '{}' does not exist yet", filePath);
+			LOGGER.debug("File '{}' does not exist yet", filePath);
 			return false;
 		}
 		if (Files.isDirectory(filePath)) {
-			logger.debug("File '{}' exists, but is a directory", filePath);
+			LOGGER.debug("File '{}' exists, but is a directory", filePath);
 			return false;
 		}
 		var checksumPath = getChecksumPath(filePath);
 		if (!Files.exists(checksumPath)) {
-			logger.debug("File '{}' exists, but checksum file '{}' does not", filePath, checksumPath);
+			LOGGER.debug("File '{}' exists, but checksum file '{}' does not", filePath, checksumPath);
 			return false;
 		}
 		if (Files.isDirectory(checksumPath)) {
-			logger.debug("Checksum file '{}' exists, but is a directory", checksumPath);
+			LOGGER.debug("Checksum file '{}' exists, but is a directory", checksumPath);
 			return false;
 		}
 		try {
 			var actualChecksum = computeChecksum(filePath, CHECKSUM_ALGORITHM);
 			var expectedChecksum = readTextFile(checksumPath, StandardCharsets.ISO_8859_1);
-			logger.debug("Expected checksum: {}, actual checksum: {}", expectedChecksum, actualChecksum);
+			LOGGER.debug("Expected checksum: {}, actual checksum: {}", expectedChecksum, actualChecksum);
 			return Objects.equals(expectedChecksum, actualChecksum);
 		} catch (final IOException ignored) {
 			return false;

lib/src/main/java/com/diffplug/spotless/biome/BiomeSettings.java

@@ -22,7 +22,7 @@
  * Settings and constants for Biome to use.
  */
 public final class BiomeSettings {
-	private static final Logger logger = LoggerFactory.getLogger(BiomeSettings.class);
+	private static final Logger LOGGER = LoggerFactory.getLogger(BiomeSettings.class);
 
 	private static final String CONFIG_NAME = "biome.json";
 	private static final String DEFAULT_VERSION = "1.2.0";
@@ -106,7 +106,7 @@ public static boolean versionHigherThanOrEqualTo(String version, int major, int
 			}
 			return actualMajor == major && actualMinor == minor && actualPatch == patch;
 		} catch (final Exception e) {
-			logger.warn("Failed to parse biome version string '{}'. Expected format is 'major.minor.patch'.", version, e);
+			LOGGER.warn("Failed to parse biome version string '{}'. Expected format is 'major.minor.patch'.", version, e);
 			return false;
 		}
 	}