Support multiple file extensions per language

Fixes #71

xtext-gradle-plugin/src/integTest/java/org/xtext/gradle/test/BuildingAPlainLanguageProject.xtend

@@ -1,5 +1,6 @@
 package org.xtext.gradle.test
 
+import org.gradle.testkit.runner.TaskOutcome
 import org.junit.Test
 
 //TODO use a different language than Xtend
@@ -125,4 +126,17 @@ class BuildingAPlainLanguageProject extends AbstractIntegrationTest {
 		// then
 		staleFile.shouldExist
 	}
+
+	/*
+	 * We currently lack a language with multiple file extensions,
+	 * so we test that an empty set will be detected as "no sources"
+	 * to at least have some coverage for the fact that fileExtensions
+	 * is indeed a Set.
+	 */
+	@Test
+	def void canOverrideFileExtensions() {
+		buildFile << '''xtext.languages.xtend.fileExtensions = []'''
+		file('src/main/java/HelloWorld.xtend').content = '''class HelloWorld {}'''
+		build('generateXtext').xtextTask.shouldBe(TaskOutcome.NO_SOURCE)
+	}
 }

xtext-gradle-plugin/src/integTest/java/org/xtext/gradle/test/GradleBuildTester.xtend

@@ -101,14 +101,22 @@ class GradleBuildTester extends ExternalResource {
 	}
 
 	def void shouldBeUpToDate(BuildTask task) {
-		if(task.outcome != TaskOutcome.UP_TO_DATE) {
-			fail('''Expected task '«task.path»' to be <UP-TO-DATE> but was: <«task.outcome»>''')
+		task.shouldBe(TaskOutcome.UP_TO_DATE)
+	}
+
+	def void shouldBe(BuildTask task, TaskOutcome outcome) {
+		if(task.outcome != outcome) {
+			fail('''Expected task '«task.path»' to be «outcome» but was: <«task.outcome»>''')
 		}
 	}
 
 	def void shouldNotBeUpToDate(BuildTask task) {
-		if(task.outcome == TaskOutcome.UP_TO_DATE) {
-			fail('''Expected task '«task.path»' not to be <UP-TO-DATE> but it was.''')
+		task.shouldNotBe(TaskOutcome.UP_TO_DATE)
+	}
+
+	def void shouldNotBe(BuildTask task, TaskOutcome outcome) {
+		if(task.outcome == outcome) {
+			fail('''Expected task '«task.path»' not to be «outcome» but it was.''')
 		}
 	}
 

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

@@ -26,7 +26,6 @@ class XtendLanguageBasePlugin implements Plugin<Project> {
 		]
 		xtext = project.extensions.getByType(XtextExtension)
 		val xtend = xtext.languages.create("xtend") [
-			fileExtension = "xtend"
 			setup = "org.eclipse.xtend.core.XtendStandaloneSetup"
 			generator.outlet => [
 				producesJava = true

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

@@ -130,7 +130,9 @@ class XtextBuilderPlugin implements Plugin<Project> {
 		project.afterEvaluate [
 			xtext.languages.all [ lang |
 				xtext.sourceSets.all [
-					filter.include("**/*." + lang.fileExtension)
+					lang.fileExtensions.forEach[ ext |
+						filter.include("**/*." + ext)
+					]
 				]
 			]
 		]

xtext-gradle-plugin/src/main/java/org/xtext/gradle/tasks/XtextExtension.xtend

@@ -22,6 +22,7 @@ import org.xtext.gradle.tasks.internal.DefaultXtextSourceDirectorySet
 import org.xtext.gradle.tasks.internal.Version
 
 import static extension org.xtext.gradle.GradleExtensions.*
+import java.util.Set
 
 class XtextExtension {
 	@Accessors String version
@@ -89,7 +90,7 @@ class XtextExtension {
 class Language implements Named {
 	@Input val String name
 	@Input String qualifiedName
-	@Input String fileExtension
+	@Input Set<String> fileExtensions
 	@Input String setup
 	@Nested val GeneratorConfig generator
 	@Nested val DebuggerConfig debugger
@@ -101,14 +102,22 @@ class Language implements Named {
 		this.generator = project.instantiate(typeof(GeneratorConfig), project, this)
 		this.debugger = project.instantiate(typeof(DebuggerConfig))
 		this.validator = project.instantiate(typeof(ValidatorConfig))
+		fileExtensions = newLinkedHashSet(name)
 	}
 
 	def getQualifiedName() {
 		qualifiedName ?: setup.replace("StandaloneSetup", "")
 	}
 
+	@Internal
+	@Deprecated
 	def getFileExtension() {
-		fileExtension ?: name
+		fileExtensions.head
+	}
+
+	@Deprecated
+	def setFileExtension(String ext) {
+		fileExtensions = newLinkedHashSet(ext)
 	}
 
 	def generator(Action<GeneratorConfig> action) {

xtext-gradle-plugin/src/main/java/org/xtext/gradle/tasks/XtextGenerate.xtend

@@ -1,6 +1,8 @@
 package org.xtext.gradle.tasks;
 
 import com.google.common.base.Charsets
+import com.google.common.io.Files
+import com.google.common.io.Resources
 import java.io.File
 import java.util.Collection
 import java.util.Set
@@ -18,16 +20,14 @@ import org.gradle.api.tasks.SkipWhenEmpty
 import org.gradle.api.tasks.TaskAction
 import org.gradle.api.tasks.incremental.IncrementalTaskInputs
 import org.gradle.api.tasks.util.PatternSet
+import org.xtext.gradle.XtextBuilderPlugin
 import org.xtext.gradle.protocol.GradleBuildRequest
 import org.xtext.gradle.protocol.GradleGeneratorConfig
 import org.xtext.gradle.protocol.GradleInstallDebugInfoRequest
 import org.xtext.gradle.protocol.GradleInstallDebugInfoRequest.GradleSourceInstallerConfig
 import org.xtext.gradle.protocol.GradleOutputConfig
 import org.xtext.gradle.protocol.IncrementalXtextBuilder
 import org.xtext.gradle.tasks.internal.IncrementalXtextBuilderProvider
-import com.google.common.io.Resources
-import org.xtext.gradle.XtextBuilderPlugin
-import com.google.common.io.Files
 
 class XtextGenerate extends DefaultTask {
 
@@ -66,7 +66,9 @@ class XtextGenerate extends DefaultTask {
 	def getMainSources() {
 		val patterns = new PatternSet
 		languages.filter[!generator.outlets.empty].forEach [lang |
-			patterns.include("**/*." + lang.fileExtension)
+			lang.fileExtensions.forEach[ ext |
+				patterns.include("**/*." + ext)
+			]
 		]
 		project.files(sources.srcDirs).asFileTree.matching(patterns)
 	}
@@ -163,11 +165,16 @@ class XtextGenerate extends DefaultTask {
 		val request = new GradleInstallDebugInfoRequest => [
 			generatedJavaFiles = generatedFiles.filter[name.endsWith(".java")].toSet
 			it.classesDir = classesDir
-			sourceInstallerByFileExtension = languages.toMap[fileExtension].mapValues[lang|
-				new GradleSourceInstallerConfig() => [
-					sourceInstaller = lang.debugger.sourceInstaller
-					hideSyntheticVariables = lang.debugger.hideSyntheticVariables
+			sourceInstallerByFileExtension = newLinkedHashMap
+
+			languages.forEach[lang|
+				lang.fileExtensions.forEach[ext |
+					sourceInstallerByFileExtension.put(ext, new GradleSourceInstallerConfig() => [
+						sourceInstaller = lang.debugger.sourceInstaller
+						hideSyntheticVariables = lang.debugger.hideSyntheticVariables
+					])
 				]
+
 			]
 		]
 		builder.installDebugInfo(request)