Convert scalafmt integration to use a compile-only sourceset

CHANGES.md

@@ -10,6 +10,7 @@ This document is intended for Spotless developers.
 We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (starting after version `1.27.0`).
 
 ## [Unreleased]
+* Converted `scalafmt` integration to use a compile-only source set. (fixes [#524](https://github.com/diffplug/spotless/issues/524))
 
 ## [2.28.1] - 2022-08-10
 ### Fixed

lib/build.gradle

@@ -12,7 +12,8 @@ def NEEDS_GLUE = [
 	'ktfmt',
 	'ktlint',
 	'flexmark',
-	'diktat'
+	'diktat',
+	'scalafmt'
 ]
 for (glue in NEEDS_GLUE) {
 	sourceSets.register(glue) {
@@ -51,6 +52,9 @@ dependencies {
 	ktlintCompileOnly "com.pinterest.ktlint:ktlint-ruleset-experimental:$VER_KTLINT"
 	ktlintCompileOnly "com.pinterest.ktlint:ktlint-ruleset-standard:$VER_KTLINT"
 
+	String VER_SCALAFMT="3.5.9"
+	scalafmtCompileOnly "org.scalameta:scalafmt-core_2.13:$VER_SCALAFMT"
+
 	String VER_DIKTAT = "1.2.3"
 	diktatCompileOnly "org.cqfn.diktat:diktat-rules:$VER_DIKTAT"
 

lib/src/main/java/com/diffplug/spotless/scala/ScalaFmtStep.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2021 DiffPlug
+ * Copyright 2016-2022 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,13 +18,8 @@
 import java.io.File;
 import java.io.IOException;
 import java.io.Serializable;
-import java.lang.reflect.Method;
-import java.nio.charset.StandardCharsets;
-import java.nio.file.Files;
+import java.lang.reflect.Constructor;
 import java.util.Collections;
-import java.util.Objects;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 
 import javax.annotation.Nullable;
 
@@ -39,23 +34,17 @@ public class ScalaFmtStep {
 	// prevent direct instantiation
 	private ScalaFmtStep() {}
 
-	private static final Pattern VERSION_PRE_2_0 = Pattern.compile("[10]\\.(\\d+)\\.\\d+");
-	private static final Pattern VERSION_PRE_3_0 = Pattern.compile("2\\.(\\d+)\\.\\d+");
-	private static final String DEFAULT_VERSION = "3.0.8";
+	private static final String DEFAULT_VERSION = "3.5.9";
 	static final String NAME = "scalafmt";
-	static final String MAVEN_COORDINATE_PRE_2_0 = "com.geirsson:scalafmt-core_2.11:";
-	static final String MAVEN_COORDINATE_PRE_3_0 = "org.scalameta:scalafmt-core_2.11:";
 	static final String MAVEN_COORDINATE = "org.scalameta:scalafmt-core_2.13:";
 
 	public static FormatterStep create(Provisioner provisioner) {
 		return create(defaultVersion(), provisioner, null);
 	}
 
 	public static FormatterStep create(String version, Provisioner provisioner, @Nullable File configFile) {
-		Objects.requireNonNull(version, "version");
-		Objects.requireNonNull(provisioner, "provisioner");
 		return FormatterStep.createLazy(NAME,
-				() -> new State(version, provisioner, configFile),
+				() -> new State(JarState.from(MAVEN_COORDINATE + version, provisioner), configFile),
 				State::createFormat);
 	}
 
@@ -69,78 +58,16 @@ static final class State implements Serializable {
 		final JarState jarState;
 		final FileSignature configSignature;
 
-		State(String version, Provisioner provisioner, @Nullable File configFile) throws IOException {
-			String mavenCoordinate;
-			Matcher versionMatcher;
-			if ((versionMatcher = VERSION_PRE_2_0.matcher(version)).matches()) {
-				mavenCoordinate = MAVEN_COORDINATE_PRE_2_0;
-			} else if ((versionMatcher = VERSION_PRE_3_0.matcher(version)).matches()) {
-				mavenCoordinate = MAVEN_COORDINATE_PRE_3_0;
-			} else {
-				mavenCoordinate = MAVEN_COORDINATE;
-			}
-
-			this.jarState = JarState.from(mavenCoordinate + version, provisioner);
+		State(JarState jarState, @Nullable File configFile) throws IOException {
+			this.jarState = jarState;
 			this.configSignature = FileSignature.signAsList(configFile == null ? Collections.emptySet() : Collections.singleton(configFile));
 		}
 
 		FormatterFunc createFormat() throws Exception {
-			ClassLoader classLoader = jarState.getClassLoader();
-
-			// scalafmt returns instances of formatted, we get result by calling get()
-			Class<?> formatted = classLoader.loadClass("org.scalafmt.Formatted");
-			Method formattedGet = formatted.getMethod("get");
-
-			// this is how we actually do a format
-			Class<?> scalafmt = classLoader.loadClass("org.scalafmt.Scalafmt");
-			Class<?> scalaSet = classLoader.loadClass("scala.collection.immutable.Set");
-
-			Object defaultScalaFmtConfig = scalafmt.getMethod("format$default$2").invoke(null);
-			Object emptyRange = scalafmt.getMethod("format$default$3").invoke(null);
-			Method formatMethod = scalafmt.getMethod("format", String.class, defaultScalaFmtConfig.getClass(), scalaSet);
-
-			// now we just need to parse the config, if any
-			Object config;
-			if (configSignature.files().isEmpty()) {
-				config = defaultScalaFmtConfig;
-			} else {
-				File file = configSignature.getOnlyFile();
-
-				Class<?> optionCls = classLoader.loadClass("scala.Option");
-				Class<?> configCls = classLoader.loadClass("org.scalafmt.config.Config");
-				Class<?> scalafmtCls = classLoader.loadClass("org.scalafmt.Scalafmt");
-
-				Object configured;
-
-				try {
-					// scalafmt >= 1.6.0
-					Method parseHoconConfig = scalafmtCls.getMethod("parseHoconConfig", String.class);
-
-					String configStr = new String(Files.readAllBytes(file.toPath()), StandardCharsets.UTF_8);
-
-					configured = parseHoconConfig.invoke(null, configStr);
-				} catch (NoSuchMethodException e) {
-					// scalafmt >= v0.7.0-RC1 && scalafmt < 1.6.0
-					Method fromHocon = configCls.getMethod("fromHoconString", String.class, optionCls);
-					Object fromHoconEmptyPath = configCls.getMethod("fromHoconString$default$2").invoke(null);
-
-					String configStr = new String(Files.readAllBytes(file.toPath()), StandardCharsets.UTF_8);
-
-					configured = fromHocon.invoke(null, configStr, fromHoconEmptyPath);
-				}
-
-				config = invokeNoArg(configured, "get");
-			}
-			return input -> {
-				Object resultInsideFormatted = formatMethod.invoke(null, input, config, emptyRange);
-				return (String) formattedGet.invoke(resultInsideFormatted);
-			};
+			final ClassLoader classLoader = jarState.getClassLoader();
+			final Class<?> formatterFunc = classLoader.loadClass("com.diffplug.spotless.glue.scalafmt.ScalafmtFormatterFunc");
+			final Constructor<?> constructor = formatterFunc.getConstructor(FileSignature.class);
+			return (FormatterFunc) constructor.newInstance(this.configSignature);
 		}
 	}
-
-	private static Object invokeNoArg(Object obj, String toInvoke) throws Exception {
-		Class<?> clazz = obj.getClass();
-		Method method = clazz.getMethod(toInvoke);
-		return method.invoke(obj);
-	}
 }

lib/src/scalafmt/java/com/diffplug/spotless/glue/scalafmt/ScalafmtFormatterFunc.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2022 DiffPlug
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.diffplug.spotless.glue.scalafmt;
+
+import java.io.File;
+import java.lang.reflect.Method;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+
+import org.scalafmt.Scalafmt;
+import org.scalafmt.config.ScalafmtConfig;
+import org.scalafmt.config.ScalafmtConfig$;
+
+import com.diffplug.spotless.FileSignature;
+import com.diffplug.spotless.FormatterFunc;
+
+import scala.collection.immutable.Set$;
+
+public class ScalafmtFormatterFunc implements FormatterFunc {
+	private final FileSignature configSignature;
+
+	public ScalafmtFormatterFunc(FileSignature configSignature) {
+		this.configSignature = configSignature;
+	}
+
+	@Override
+	public String apply(String input) throws Exception {
+		ScalafmtConfig config;
+		if (configSignature.files().isEmpty()) {
+			// Note that reflection is used here only because Scalafmt has a method called
+			// default which happens to be a reserved Java keyword. The only way to call
+			// such methods is by reflection, see
+			// https://vlkan.com/blog/post/2015/11/20/scala-method-with-java-reserved-keyword/
+			Method method = ScalafmtConfig$.MODULE$.getClass().getDeclaredMethod("default");
+			config = (ScalafmtConfig) method.invoke(ScalafmtConfig$.MODULE$);
+		} else {
+			File file = configSignature.getOnlyFile();
+			String configStr = new String(Files.readAllBytes(file.toPath()), StandardCharsets.UTF_8);
+			config = Scalafmt.parseHoconConfig(configStr).get();
+		}
+		return Scalafmt.format(input, config, Set$.MODULE$.empty()).get();
+	}
+}

testlib/src/main/resources/scala/scalafmt/scalafmt.conf

@@ -1,2 +1,4 @@
+version = 3.5.9
+runner.dialect = scala213
 style = defaultWithAlign # For pretty alignment.
 maxColumn = 20           # For my teensy narrow display