Merge pull request #102 from xtext/cd_issue101

[#101] Made Version Detection more robust regaring usage in java 9

Author: oehme

xtext-gradle-plugin/src/main/java/org/xtext/gradle/XtextBuilderPlugin.xtend

@@ -8,6 +8,7 @@ import org.gradle.api.GradleException
 import org.gradle.api.Plugin
 import org.gradle.api.Project
 import org.gradle.api.artifacts.Configuration
+import org.gradle.api.file.FileCollection
 import org.gradle.api.plugins.BasePlugin
 import org.gradle.api.plugins.JavaBasePlugin
 import org.gradle.api.plugins.JavaPluginConvention
@@ -16,13 +17,13 @@ import org.gradle.api.tasks.compile.JavaCompile
 import org.gradle.plugins.ide.eclipse.EclipsePlugin
 import org.gradle.plugins.ide.eclipse.model.EclipseModel
 import org.xtext.gradle.tasks.Outlet
+import org.xtext.gradle.tasks.XtextClasspathInferrer
 import org.xtext.gradle.tasks.XtextEclipseSettings
 import org.xtext.gradle.tasks.XtextExtension
 import org.xtext.gradle.tasks.XtextGenerate
 
 import static extension org.xtext.gradle.GradleExtensions.*
-import org.gradle.api.file.FileCollection
-import org.xtext.gradle.tasks.XtextClasspathInferrer
+import static org.xtext.gradle.XtextBuilderPluginVersion.*
 
 class XtextBuilderPlugin implements Plugin<Project> {
 
@@ -54,7 +55,7 @@ class XtextBuilderPlugin implements Plugin<Project> {
 				xtextClasspath = project.files(new Callable<FileCollection>() {
 					FileCollection inferredClasspath
 					override call() throws Exception {
-						if (inferredClasspath == null) {
+						if (inferredClasspath === null) {
 							inferredClasspath = inferXtextClasspath(classpath)
 						}
 						inferredClasspath
@@ -81,14 +82,14 @@ class XtextBuilderPlugin implements Plugin<Project> {
 	private def automaticallyInferXtextCoreClasspath() {
 		xtext.classpathInferrers += new XtextClasspathInferrer() {
 			override inferXtextClasspath(FileCollection xtextClasspath, FileCollection classpath) {
-				val xtextBuilder =  project.dependencies.externalModule('''org.xtext:xtext-gradle-builder:«pluginVersion»''')
+				val xtextBuilder =  project.dependencies.externalModule('''org.xtext:xtext-gradle-builder:«PLUGIN_VERSION»''')
 				val xtextTooling = project.configurations.detachedConfiguration(xtextBuilder)
 				xtext.makeXtextCompatible(xtextTooling)
 				xtext.forceXtextVersion(xtextTooling, new Function0<String>() {
 					String version = null
 
 					override apply() {
-						if (version == null) {
+						if (version === null) {
 							version = xtext.getXtextVersion(classpath) ?: xtext.getXtextVersion(xtextClasspath)
 							if (version === null) {
 								throw new GradleException('''Could not infer Xtext classpath, because xtext.version was not set and no xtext libraries were found on the «classpath» classpath''')
@@ -102,10 +103,6 @@ class XtextBuilderPlugin implements Plugin<Project> {
 		}
 	}
 
-	private def String getPluginVersion() {
-		XtextBuilderPlugin.package.implementationVersion
-	}
-
 	private def configureOutletDefaults() {
 		xtext.languages.all [ language |
 			language.generator.outlets.create(Outlet.DEFAULT_OUTLET)

xtext-gradle-plugin/src/main/java/org/xtext/gradle/XtextBuilderPluginVersion.java

@@ -0,0 +1,29 @@
+package org.xtext.gradle;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.jar.Manifest;
+
+public class XtextBuilderPluginVersion {
+	
+	public static final String PLUGIN_VERSION;
+	
+	static {
+		String implementationVersion = XtextBuilderPluginVersion.class.getPackage().getImplementationVersion();
+		if (implementationVersion != null) {
+			PLUGIN_VERSION = implementationVersion;
+		} else {
+			String version = null;
+			try (InputStream stream = XtextBuilderPluginVersion.class.getResourceAsStream("/META-INF/MANIFEST.MF")) {
+				if (stream != null) {
+					Manifest mf = new Manifest(stream);
+					version = mf.getMainAttributes().getValue("Implementation-Version");
+				}
+			} catch (IOException e) {
+			}
+			PLUGIN_VERSION = version;
+			
+		}
+	}
+
+}