Added support for Maven POM sorting/formatting

lib/build.gradle

@@ -6,15 +6,35 @@ version = rootProject.spotlessChangelog.versionNext
 apply from: rootProject.file('gradle/java-setup.gradle')
 apply from: rootProject.file('gradle/java-publish.gradle')
 
+sourceSets {
+	sortPom {
+		compileClasspath += sourceSets.main.output
+		runtimeClasspath += sourceSets.main.output
+
+		java {
+		}
+	}
+}
+
 dependencies {
 	// zero runtime reqs is a hard requirements for spotless-lib
 	// if you need a dep, put it in lib-extra
 	testImplementation "org.junit.jupiter:junit-jupiter:${VER_JUNIT}"
 	testImplementation "org.assertj:assertj-core:${VER_ASSERTJ}"
 	testImplementation "com.diffplug.durian:durian-testlib:${VER_DURIAN}"
+
+	// used for pom sorting
+	sortPomCompileOnly 'com.github.ekryd.sortpom:sortpom-sorter:3.0.0'
 }
 
 // we'll hold the core lib to a high standard
 spotbugs { reportLevel = 'low' } // low|medium|high (low = sensitive to even minor mistakes)
 
 test { useJUnitPlatform() }
+
+jar {
+	// Add directories with generated sources (might be several - one for every supported language).
+	from sourceSets.sortPom.output.classesDirs
+	// Add output directories of the sourceset's resources.
+	from sourceSets.sortPom.output.resourcesDir
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 DiffPlug
+ * Copyright 2016-2021 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,11 +15,13 @@
  */
 package com.diffplug.spotless;
 
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
 import java.net.URL;
 import java.net.URLClassLoader;
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
+import java.nio.ByteBuffer;
+import java.security.ProtectionDomain;
 import java.util.Objects;
 
 import javax.annotation.Nullable;
@@ -29,37 +31,31 @@
  * path of URLs.<br/>
  * Features shall be independent from build tools. Hence the class loader of the
  * underlying build tool is e.g. skipped during the the search for classes.<br/>
- * Only {@link #BUILD_TOOLS_PACKAGES } are explicitly looked up from the class loader of
- * the build tool and the provided URLs are ignored. This allows the feature to use
- * distinct functionality of the build tool.
+ *
+ * For `com.diffplug.spotless.glue.`, classes are redefined from within the lib jar
+ * but linked against the `Url[]`. This allows us to ship classfiles which function as glue
+ * code but delay linking/definition to runtime after the user has specified which version
+ * of the formatter they want.
+ *
+ *  For `"org.slf4j.` and (`com.diffplug.spotless.` but not `com.diffplug.spotless.extra.`)
+ * 	the classes are loaded from the buildToolClassLoader.
  */
 class FeatureClassLoader extends URLClassLoader {
 	static {
 		ClassLoader.registerAsParallelCapable();
 	}
 
-	/**
-	 * The following packages must be provided by the build tool or the corresponding Spotless plugin:
-	 * <ul>
-	 *   <li>org.slf4j - SLF4J API must be provided. If no SLF4J binding is provided, log messages are dropped.</li>
-	 * </ul>
-	 */
-	static final List<String> BUILD_TOOLS_PACKAGES = Collections.unmodifiableList(Arrays.asList("org.slf4j."));
-	// NOTE: if this changes, you need to also update the `JarState.getClassLoader` methods.
-
 	private final ClassLoader buildToolClassLoader;
 
 	/**
 	 * Constructs a new FeatureClassLoader for the given URLs, based on an {@code URLClassLoader},
-	 * using the system class loader as parent. For {@link #BUILD_TOOLS_PACKAGES }, the build
-	 * tool class loader is used.
+	 * using the system class loader as parent.
 	 *
 	 * @param urls the URLs from which to load classes and resources
 	 * @param buildToolClassLoader The build tool class loader
 	 * @exception  SecurityException  If a security manager exists and prevents the creation of a class loader.
 	 * @exception  NullPointerException if {@code urls} is {@code null}.
 	 */
-
 	FeatureClassLoader(URL[] urls, ClassLoader buildToolClassLoader) {
 		super(urls, getParentClassLoader());
 		Objects.requireNonNull(buildToolClassLoader);
@@ -68,12 +64,53 @@ class FeatureClassLoader extends URLClassLoader {
 
 	@Override
 	protected Class<?> findClass(String name) throws ClassNotFoundException {
-		for (String buildToolPackage : BUILD_TOOLS_PACKAGES) {
-			if (name.startsWith(buildToolPackage)) {
-				return buildToolClassLoader.loadClass(name);
+		if (name.startsWith("com.diffplug.spotless.glue.")) {
+			String path = name.replace('.', '/') + ".class";
+			URL url = findResource(path);
+			if (url == null) {
+				throw new ClassNotFoundException(name);
+			}
+			try {
+				return defineClass(name, urlToByteBuffer(url), (ProtectionDomain) null);
+			} catch (IOException e) {
+				throw new ClassNotFoundException(name, e);
 			}
+		} else if (useBuildToolClassLoader(name)) {
+			return buildToolClassLoader.loadClass(name);
+		} else {
+			return super.findClass(name);
+		}
+	}
+
+	private static boolean useBuildToolClassLoader(String name) {
+		if (name.startsWith("org.slf4j.")) {
+			return true;
+		} else if (!name.startsWith("com.diffplug.spotless.extra") && name.startsWith("com.diffplug.spotless.")) {
+			return true;
+		} else {
+			return false;
+		}
+	}
+
+	@Override
+	public URL findResource(String name) {
+		URL resource = super.findResource(name);
+		if (resource != null) {
+			return resource;
+		}
+		return buildToolClassLoader.getResource(name);
+	}
+
+	private static ByteBuffer urlToByteBuffer(URL url) throws IOException {
+		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+		int nRead;
+		byte[] data = new byte[1024];
+		InputStream inputStream = url.openStream();
+		while ((nRead = inputStream.read(data, 0, data.length)) != -1) {
+			buffer.write(data, 0, nRead);
 		}
-		return super.findClass(name);
+		buffer.flush();
+		return ByteBuffer.wrap(buffer.toByteArray());
 	}
 
 	/**

lib/src/main/java/com/diffplug/spotless/pom/SortPomCfg.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2021 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.pom;
+
+import java.io.Serializable;
+
+// Class and members must be public, otherwise we get failed to access class com.diffplug.spotless.pom.SortPomInternalState from class com.diffplug.spotless.pom.SortPomFormatterFunc (com.diffplug.spotless.pom.SortPomInternalState is in unnamed module of loader org.codehaus.plexus.classworlds.realm.ClassRealm @682bd3c4; com.diffplug.spotless.pom.SortPomFormatterFunc is in unnamed module of loader com.diffplug.spotless.pom.DelegatingClassLoader @573284a5)
+public class SortPomCfg implements Serializable {
+	private static final long serialVersionUID = 1L;
+
+	public String encoding = "UTF-8";
+
+	public String lineSeparator = System.getProperty("line.separator");
+
+	public boolean expandEmptyElements = true;
+
+	public boolean spaceBeforeCloseEmptyElement = false;
+
+	public boolean keepBlankLines = true;
+
+	public int nrOfIndentSpace = 2;
+
+	public boolean indentBlankLines = false;
+
+	public boolean indentSchemaLocation = false;
+
+	public String predefinedSortOrder = "recommended_2008_06";
+
+	public String sortOrderFile = null;
+
+	public String sortDependencies = null;
+
+	public String sortDependencyExclusions = null;
+
+	public String sortPlugins = null;
+
+	public boolean sortProperties = false;
+
+	public boolean sortModules = false;
+
+	public boolean sortExecutions = false;
+}

lib/src/main/java/com/diffplug/spotless/pom/SortPomStep.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2021 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.pom;
+
+import java.io.IOException;
+import java.io.Serializable;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+
+import com.diffplug.spotless.FormatterFunc;
+import com.diffplug.spotless.FormatterStep;
+import com.diffplug.spotless.JarState;
+import com.diffplug.spotless.Provisioner;
+
+public class SortPomStep {
+	public static final String NAME = "sortPom";
+
+	private SortPomStep() {}
+
+	private SortPomCfg cfg;
+
+	public static FormatterStep create(SortPomCfg cfg, Provisioner provisioner) {
+		return FormatterStep.createLazy(NAME, () -> new State(cfg, provisioner), State::createFormat);
+	}
+
+	static class State implements Serializable {
+		SortPomCfg cfg;
+		JarState jarState;
+
+		public State(SortPomCfg cfg, Provisioner provisioner) throws IOException {
+			this.cfg = cfg;
+			this.jarState = JarState.from("com.github.ekryd.sortpom:sortpom-sorter:3.0.0", provisioner);
+		}
+
+		FormatterFunc createFormat() throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, InstantiationException, IllegalAccessException {
+			Class<?> formatterFunc = jarState.getClassLoader().loadClass("com.diffplug.spotless.glue.pom.SortPomFormatterFunc");
+			Constructor<?> constructor = formatterFunc.getConstructor(SortPomCfg.class);
+			return (FormatterFunc) constructor.newInstance(cfg);
+		}
+	}
+}

lib/src/sortPom/java/com/diffplug/spotless/glue/pom/SortPomFormatterFunc.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2021 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.pom;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.util.logging.Logger;
+
+import org.apache.commons.io.IOUtils;
+
+import com.diffplug.spotless.FormatterFunc;
+import com.diffplug.spotless.pom.SortPomCfg;
+
+import sortpom.SortPomImpl;
+import sortpom.logger.SortPomLogger;
+import sortpom.parameter.PluginParameters;
+
+public class SortPomFormatterFunc implements FormatterFunc {
+	private static final Logger logger = Logger.getLogger(SortPomFormatterFunc.class.getName());
+	private final SortPomCfg cfg;
+
+	public SortPomFormatterFunc(SortPomCfg cfg) {
+		this.cfg = cfg;
+	}
+
+	@Override
+	public String apply(String input) throws Exception {
+		// SortPom expects a file to sort, so we write the inpout into a temporary file
+		File pom = File.createTempFile("pom", ".xml");
+		pom.deleteOnExit();
+		IOUtils.write(input, new FileOutputStream(pom), cfg.encoding);
+		SortPomImpl sortPom = new SortPomImpl();
+		sortPom.setup(new MySortPomLogger(), PluginParameters.builder()
+				.setPomFile(pom)
+				.setFileOutput(false, null, null, false)
+				.setEncoding(cfg.encoding)
+				.setFormatting(cfg.lineSeparator, cfg.expandEmptyElements, cfg.spaceBeforeCloseEmptyElement, cfg.keepBlankLines)
+				.setIndent(cfg.nrOfIndentSpace, cfg.indentBlankLines, cfg.indentSchemaLocation)
+				.setSortOrder(cfg.sortOrderFile, cfg.predefinedSortOrder)
+				.setSortEntities(cfg.sortDependencies, cfg.sortDependencyExclusions, cfg.sortPlugins, cfg.sortProperties, cfg.sortModules, cfg.sortExecutions)
+				.setTriggers(false)
+				.build());
+		sortPom.sortPom();
+		return IOUtils.toString(new FileInputStream(pom), cfg.encoding);
+	}
+
+	private static class MySortPomLogger implements SortPomLogger {
+		@Override
+		public void warn(String content) {
+			logger.warning(content);
+		}
+
+		@Override
+		public void info(String content) {
+			logger.info(content);
+		}
+
+		@Override
+		public void error(String content) {
+			logger.severe(content);
+		}
+	}
+}

plugin-maven/build.gradle

@@ -63,6 +63,7 @@ String libVersion = version.endsWith('-SNAPSHOT') ?
 dependencies {
 	if (version.endsWith('-SNAPSHOT') || (rootProject.spotlessChangelog.versionNext == rootProject.spotlessChangelog.versionLast)) {
 		implementation project(':lib')
+		implementation project(':lib').sourceSets.sortPom.output
 		implementation project(':lib-extra')
 	} else {
 		implementation "com.diffplug.spotless:spotless-lib:${libVersion}"

plugin-maven/src/main/java/com/diffplug/spotless/maven/AbstractSpotlessMojo.java

@@ -56,6 +56,7 @@
 import com.diffplug.spotless.maven.groovy.Groovy;
 import com.diffplug.spotless.maven.java.Java;
 import com.diffplug.spotless.maven.kotlin.Kotlin;
+import com.diffplug.spotless.maven.pom.Pom;
 import com.diffplug.spotless.maven.python.Python;
 import com.diffplug.spotless.maven.scala.Scala;
 import com.diffplug.spotless.maven.sql.Sql;
@@ -120,6 +121,9 @@ public abstract class AbstractSpotlessMojo extends AbstractMojo {
 	@Parameter
 	private Antlr4 antlr4;
 
+	@Parameter
+	private Pom pom;
+
 	@Parameter
 	private Sql sql;
 
@@ -258,7 +262,7 @@ private FileLocator getFileLocator() {
 	}
 
 	private List<FormatterFactory> getFormatterFactories() {
-		return Stream.concat(formats.stream(), Stream.of(groovy, java, scala, kotlin, cpp, typescript, antlr4, sql, python))
+		return Stream.concat(formats.stream(), Stream.of(groovy, java, scala, kotlin, cpp, typescript, antlr4, pom, sql, python))
 				.filter(Objects::nonNull)
 				.collect(toList());
 	}