Refactor merge-artifacts script to a plugin

Refactor the existing merge-artifacts script to a full Gradle plugin.
The new plugin uses a 'merge' extension in favor of Gradle 'ext'
configuration and can be applied to all projects in a multi-module
build.

Any project that defines a 'merge.into' project will now implicitly
receive a dependency to that project. Furthermore other projects
with a dependency on 'merge.into' will receive a direct project
link within the IDE. For example: 'spring-webmvc-tiles3'
is merged into 'spring-webmvc' and 'spring-test-mvc' depends
on 'spring-webmvc'. Within the IDE 'spring-test-mvc' will show
dependencies to both 'spring-webmvc' and 'spring-webmvc-tiles'.

Issue: SPR-10042

build.gradle

@@ -46,6 +46,7 @@ configure(allprojects) {
 }
 
 configure(subprojects) { subproject ->
+	apply plugin: MergePlugin
 	apply from: "${gradleScriptDir}/publish-maven.gradle"
 
 	jar {
@@ -432,10 +433,8 @@ project("spring-orm") {
 
 project("spring-orm-hibernate4") {
 	description = "Spring Object/Relational Mapping - Hibernate 4 support"
-	ext.mergeIntoProject = project(":spring-orm")
-	apply from: "${gradleScriptDir}/merge-artifacts.gradle"
+	merge.into = project(":spring-orm")
 	dependencies {
-		compile(project(":spring-orm").sourceSets.main.output)
 		compile(project(":spring-tx"))
 		compile(project(":spring-jdbc"))
 		optional("org.hibernate:hibernate-core:4.1.0.Final")
@@ -506,11 +505,9 @@ project("spring-webmvc") {
 
 project("spring-webmvc-tiles3") {
 	description = "Spring Framework Tiles3 Integration"
-	ext.mergeIntoProject = project(":spring-webmvc")
-	apply from: "${gradleScriptDir}/merge-artifacts.gradle"
+	merge.into = project(":spring-webmvc")
 	dependencies {
 		compile(project(":spring-context"))
-		compile(project(":spring-webmvc").sourceSets.main.output)
 		provided("javax.el:el-api:1.0")
 		provided("javax.servlet:jstl:1.2")
 		provided("javax.servlet.jsp:jsp-api:2.1")
@@ -581,13 +578,10 @@ project("spring-test") {
 
 project("spring-test-mvc") {
 	description = "Spring Test MVC Framework"
-	ext.mergeIntoProject = project(":spring-test")
-	apply from: "${gradleScriptDir}/merge-artifacts.gradle"
-	apply from: "ide.gradle"
+	merge.into = project(":spring-test")
 	dependencies {
 		optional(project(":spring-context"))
 		compile(project(":spring-webmvc"))
-		compile(project(":spring-test").sourceSets.main.output)
 		provided("javax.servlet:javax.servlet-api:3.0.1")
 		optional("org.hamcrest:hamcrest-core:1.3")
 		optional("com.jayway.jsonpath:json-path:0.8.1")
@@ -663,6 +657,7 @@ configure(rootProject) {
 	description = "Spring Framework"
 
 	apply plugin: "docbook-reference"
+	apply plugin: "groovy"
 	apply from: "${gradleScriptDir}/jdiff.gradle"
 
 	reference {
@@ -674,6 +669,8 @@ configure(rootProject) {
 	configurations.archives.artifacts.clear()
 
 	dependencies { // for integration tests
+		compile gradleApi()
+		groovy localGroovy()
 		testCompile(project(":spring-core"))
 		testCompile(project(":spring-beans"))
 		testCompile(project(":spring-aop"))

buildsrc/src/main/groovy/MergePlugin.groovy

@@ -0,0 +1,130 @@
+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.*
+
+/**
+ * Gradle plugin that allows projects to merged together. Primarily developed to
+ * allow Spring to support multiple multiple incompatible versions of third-party
+ * dependencies (for example Hibernate v3 and v4).
+ * <p>
+ * The 'merge' extension should be used to define how projects are merged, for example:
+ * <pre>
+ * configure(subprojects) {
+ *     apply plugin: MergePlugin
+ * }
+ *
+ * project("myproject") {
+ * }
+ *
+ * project("myproject-extra") {
+ *     merge.into = project("myproject")
+ * }
+ * </pre>
+ * <p>
+ * This plugin adds two new configurations:
+ * <ul>
+ * <li>merging - Contains the projects being merged into this project<li>
+ * <li>runtimeMerge - Contains all dependencies that are merge projects. These are used
+ * to allow an IDE to reference merge projects.</li>
+ * <ul>
+ *
+ * @author Rob Winch
+ * @author Phillip Webb
+ */
+class MergePlugin implements Plugin<Project> {
+
+	private static boolean attachedProjectsEvaluated;
+
+	public void apply(Project project) {
+		project.plugins.apply(MavenPlugin)
+		project.plugins.apply(EclipsePlugin)
+		project.plugins.apply(IdeaPlugin)
+
+		MergeModel model = project.extensions.create("merge", MergeModel)
+		project.configurations.add("merging")
+		Configuration runtimeMerge = project.configurations.add("runtimeMerge")
+
+		// Ensure the IDE can reference merged projects
+		project.eclipse.classpath.plusConfigurations += [runtimeMerge]
+		project.idea.module.scopes.PROVIDED.plus += runtimeMerge
+
+		// Hook to perform the actual merge logic
+		project.afterEvaluate{
+			if(it.merge.into != null) {
+				setup(it)
+			}
+		}
+
+		// Hook to build runtimeMerge dependencies
+		if(!attachedProjectsEvaluated) {
+			project.gradle.projectsEvaluated{
+				postProcessProjects(it)
+			}
+			attachedProjectsEvaluated  = true;
+		}
+	}
+
+	private void setup(Project project) {
+		project.merge.into.dependencies.add("merging", project)
+		project.dependencies.add("provided", project.merge.into.sourceSets.main.output)
+		project.dependencies.add("runtimeMerge", project.merge.into)
+		setupTaskDependencies(project)
+		setupMaven(project)
+	}
+
+	private void setupTaskDependencies(Project project) {
+		// invoking a task will invoke the task with the same name on 'into' project
+		["sourcesJar", "jar", "javadocJar", "javadoc", "install", "artifactoryPublish"].each {
+			def task = project.tasks.findByPath(it)
+			if(task) {
+				task.enabled = false
+				task.dependsOn(project.merge.into.tasks.findByPath(it))
+			}
+		}
+
+		// update 'into' project artifacts to contain the source artifact contents
+		project.merge.into.sourcesJar.from(project.sourcesJar.source)
+		project.merge.into.jar.from(project.jar.source)
+		project.merge.into.javadoc {
+			source += project.javadoc.source
+			classpath += project.javadoc.classpath
+		}
+	}
+
+	private void setupMaven(Project project) {
+		project.configurations.each { configuration ->
+			Conf2ScopeMapping mapping = project.conf2ScopeMappings.getMapping([configuration])
+			if(mapping.scope) {
+				Configuration intoConfiguration = project.merge.into.configurations.add(
+					project.name + "-" + configuration.name)
+				intoConfiguration.dependencies.addAll(configuration.dependencies)
+				project.merge.into.install.repositories.mavenInstaller.pom.scopeMappings.addMapping(
+					mapping.priority + 100, intoConfiguration, mapping.scope)
+			}
+		}
+	}
+
+	private postProcessProjects(Gradle gradle) {
+		gradle.allprojects(new Action<Project>() {
+			public void execute(Project project) {
+				project.configurations.getByName("runtime").allDependencies.withType(ProjectDependency).each{
+					Configuration dependsOnMergedFrom = it.dependencyProject.configurations.getByName("merging");
+					dependsOnMergedFrom.dependencies.each{ dep ->
+						project.dependencies.add("runtimeMerge", dep.dependencyProject)
+					}
+				}
+			}
+		});
+	}
+}
+
+class MergeModel {
+	Project into;
+}

gradle/merge-artifacts.gradle

@@ -1,62 +0,0 @@
-/**
- * Will merge the artifacts of the current project into mergeIntoProject. For example, to
- * bundle spring-test-mvc in spring-test"s jars. This script will perform the following
- * steps:
- *
- * - Ensure that jar tasks of the project being merged from will execute the tasks of the
- *   project being merged into
- *
- * - Add the project being merged into to the classpath of the project being merged from
- *
- * - Update the pom.xml of the project being merged into to contain the entries from the
- *   project being merged from
- *
- * Example Usage:
- *
- *   ext.mergeIntoProject = project(":spring-test")
- *   apply from: "${rootProject.projectDir}/gradle/merge-artifacts.gradle"
- */
-
-def mergeFromProject = project
-
-// invoking a task on mergeFromProject will invoke the task with the same name on mergeIntoProject
-def taskNamesToMerge = ["sourcesJar","jar","javadocJar","javadoc","install","artifactoryPublish"]
-taskNamesToMerge.each { taskName ->
-	def taskToRemove = mergeFromProject.tasks.findByPath(taskName)
-	if(taskToRemove) {
-		taskToRemove.enabled = false
-		taskToRemove.dependsOn mergeIntoProject."$taskName"
-	}
-}
-
-// update mergeIntoProject artifacts to contain the mergeFromProject artifact contents
-mergeIntoProject."sourcesJar" {
-	from mergeFromProject.sourcesJar.source
-}
-mergeIntoProject."jar" {
-	from mergeFromProject.jar.source
-}
-mergeIntoProject."javadoc" {
-	source += mergeFromProject.javadoc.source
-	classpath += mergeFromProject.javadoc.classpath
-}
-
-// Update mergeIntoProject to contain additional configurations that contains all the dependencies from mergeFromProject
-// so that Maven pom generation works
-gradle.taskGraph.whenReady {
-	mergeFromProject.configurations.archives.artifacts.clear()
-
-	mergeFromProject.configurations.each { config->
-		def mapping = mergeFromProject.conf2ScopeMappings.getMapping([config])
-		if(mapping.scope) {
-			def newConfigName = mergeFromProject.name + "-"+ config.name
-			mergeIntoProject.configurations.add(newConfigName)
-			config.dependencies.each { dependency ->
-				mergeIntoProject.dependencies.add(newConfigName, dependency)
-			}
-			configure(mergeIntoProject.install.repositories.mavenInstaller.pom.scopeMappings) {
-				addMapping(mapping.priority + 100, mergeIntoProject.configurations."$newConfigName", mapping.scope)
-			}
-		}
-	}
-}

spring-test-mvc/ide.gradle

@@ -1,7 +0,0 @@
-import org.gradle.plugins.ide.eclipse.model.ProjectDependency
-
-// SPR-10042
-eclipse.classpath.file.whenMerged { classpath ->
-	def projectName = "spring-webmvc-tiles3"
-	classpath.entries.add(0, new ProjectDependency("/${projectName}", project(":${projectName}").path))
-}