Example SplitPackageDetectorPlugin

build.gradle

@@ -9,8 +9,11 @@ buildscript {
 }
 
 configure(rootProject) {
-    def splitFound = new org.springframework.build.gradle.SplitPackageDetector('.', logger).diagnoseSplitPackages();
-    assert !splitFound // see error log messages for details of split packages
+    apply plugin: org.springframework.build.gradle.SplitPackageDetectorPlugin
+
+	diagnoseSplitPackages {
+		inputDir = project.projectDir
+	}
 }
 
 configure(allprojects) { project ->

buildSrc/src/main/groovy/org/springframework/build/gradle/SplitPackageDetectorPlugin.groovy

@@ -0,0 +1,125 @@
+/*
+ * Copyright 2002-2012 the original author or authors.
+ *
+ * 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 org.springframework.build.gradle
+
+import java.io.File;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+import org.gradle.api.*
+import org.gradle.api.artifacts.Configuration
+import org.gradle.api.artifacts.ProjectDependency;
+import org.gradle.api.artifacts.maven.Conf2ScopeMapping
+import org.gradle.api.plugins.MavenPlugin
+import org.gradle.api.tasks.*
+import org.gradle.plugins.ide.eclipse.EclipsePlugin
+import org.gradle.plugins.ide.eclipse.model.EclipseClasspath;
+import org.gradle.plugins.ide.idea.IdeaPlugin
+import org.gradle.api.invocation.*
+
+
+class SplitPackageDetectorPlugin implements Plugin<Project> {
+	public void apply(Project project) {
+		Task diagnoseSplitPackages = project.tasks.add('diagnoseSplitPackages', SplitPackageDetectorTask.class)
+		diagnoseSplitPackages.setDescription('Detects split packages')
+		//project.tasks.findByName('build').dependsOn(diagnoseSplitPackages)
+	}
+}
+
+public class SplitPackageDetectorTask extends DefaultTask {
+	@InputDirectory
+	File inputDir
+
+	@TaskAction
+	public final void diagnoseSplitPackages() {
+		def projects = project.subprojects.findAll { it.plugins.findPlugin(org.springframework.build.gradle.MergePlugin) }.findAll { it.merge.into }
+		projects.each { p ->
+			println '    > The project directory '+ p.projectDir + ' will merge into ' + p.merge.into.projectDir
+		}
+		def splitFound = new org.springframework.build.gradle.SplitPackageDetector(inputDir.absolutePath, project.logger).diagnoseSplitPackages();
+		assert !splitFound
+	}
+}
+
+class SplitPackageDetector {
+
+	private static final String HIDDEN_DIRECTORY_PREFIX = "."
+
+	private static final String JAVA_FILE_SUFFIX = ".java"
+
+	private static final String SRC_MAIN_JAVA = "src" + File.separator + "main" + File.separator + "java"
+
+	private final Map<File, Set<String>> pkgMap = [:]
+
+	private final logger
+
+	SplitPackageDetector(baseDir, logger) {
+		this.logger = logger
+		dirList(baseDir).each { File dir ->
+			def packages = getPackagesInDirectory(dir)
+			if (!packages.isEmpty()) {
+				pkgMap.put(dir, packages)
+			}
+		}
+	}
+
+	private File[] dirList(String dir) {
+		dirList(new File(dir))
+	}
+
+	private File[] dirList(File dir) {
+		dir.listFiles({ file -> file.isDirectory() && !file.getName().startsWith(HIDDEN_DIRECTORY_PREFIX) } as FileFilter)
+	}
+
+	private Set<String> getPackagesInDirectory(File dir) {
+		def pkgs = new HashSet<String>()
+		addPackagesInDirectory(pkgs, new File(dir, SRC_MAIN_JAVA), "")
+		return pkgs;
+	}
+
+	boolean diagnoseSplitPackages() {
+		def splitFound = false;
+		def dirs = pkgMap.keySet().toArray()
+		def numDirs = dirs.length
+		for (int i = 0; i < numDirs - 1; i++) {
+			for (int j = i + 1; j < numDirs - 1; j++) {
+				def di = dirs[i]
+				def pi = new HashSet(pkgMap.get(di))
+				def dj = dirs[j]
+				def pj = pkgMap.get(dj)
+				pi.retainAll(pj)
+				if (!pi.isEmpty()) {
+					logger.error("Packages $pi are split between directories '$di' and '$dj'")
+					splitFound = true
+				}
+			}
+		}
+		return splitFound
+	}
+
+	private void addPackagesInDirectory(HashSet<String> packages, File dir, String pkg) {
+		def scanDir = new File(dir, pkg)
+		def File[] javaFiles = scanDir.listFiles({ file -> !file.isDirectory() && file.getName().endsWith(JAVA_FILE_SUFFIX) } as FileFilter)
+		if (javaFiles != null && javaFiles.length != 0) {
+			packages.add(pkg)
+		}
+		dirList(scanDir).each { File subDir ->
+			addPackagesInDirectory(packages, dir, pkg + File.separator + subDir.getName())
+		}
+	}
+}