Provide JUnit 5 equivalent of XpectRunner

This change provides a JUnit 5 alternative of the JUnit 4 XpectRunner.

To summarize the JUnit 4 specific code for Xpect tests, it looks like this:

* XpectRunner takes the @XpectTestFiles test DSLs and generates a test case for each DSL test file, i.e. it generates test cases.
* XpectFileRunner takes a DSL test file and generates test methods for a test case, these are coming from the XPECT statements (XpectInvocation or XjcTestMethod, I'm not sure which is what in the Xpect tests.
* XpectTestRunner generates a test method for a XpectInvocation.
* TestRunner generates a test method for a XjmTestMethod.

The code JUnit 4 is "transformed" as follows:

XpectRunner     -> XpectDynamicTestFactory
XpectFileRunner -> XpectDynamicTestCase
XpectTestRunner -> XpectInvocationDynamicTest
TestRunner      -> XpectDynamicTest

There is lots of supporting code that is not JUnit 4 specific, it remains functional and unchanged.

The API proposal is to add a marker interface org.eclipse.xpect.dynamic.IXpectDynamicTestFactory, that is implemented by a test case in order to enable Xpect tests (based on JUnit 5) for that test case.

There is also org.eclipse.xpect.dynamic.XpectDynamicTestCase, which has setUp() and tearDown() callbacks, called before reps. after each test method. We require these, since the JUnit 5 construct for generating tests, dynamic tests, doesn't have before/after callbacks (junit-team/junit-framework#1292 (comment), see also warning here: https://junit.org/junit5/docs/current/user-guide/#writing-tests-dynamic-tests). XpectRunner itself generates tests based on annotation values via JUnit 4 runners. XpectDynamicTestCase can be used by extending it and specifying the annotation @XpectReplace(XpectDynamicTestCase.class) at the extending class. Then importing the extended class at the client test case via e.g.:

...
@XpectImport({MyXpectDynamicTestCase.class ...})
public class MyXpectTestCase implements IXpectDynamicTestFactory {
...

Fixes: #262

Author: trancexpress

org.eclipse.xpect.ui/src/org/eclipse/xpect/ui/util/XpectFileAccess.java

@@ -30,6 +30,7 @@
 import org.eclipse.xpect.XpectFile;
 import org.eclipse.xpect.registry.ILanguageInfo;
 import org.eclipse.xpect.runner.XpectRunner;
+import org.eclipse.xpect.runner.XpectTestGlobalState;
 
 import com.google.inject.Injector;
 
@@ -67,8 +68,8 @@ protected static ResourceSet cloneResourceSet(ResourceSet rs) {
 		// need delegation or nothing because of "java" protocol
 		// result.setResourceFactoryRegistry(rs.getResourceFactoryRegistry());
 		result.setURIConverter(rs.getURIConverter());
-		if (XpectRunner.testClassloader != null) {
-			result.setClasspathURIContext(XpectRunner.testClassloader);
+		if (XpectTestGlobalState.INSTANCE.testClass() != null) {
+			result.setClasspathURIContext(XpectTestGlobalState.INSTANCE.testClass().getClassLoader());
 			result.setClasspathUriResolver(new ClassloaderClasspathUriResolver());
 		} else if (rs instanceof XtextResourceSet) {
 			XtextResourceSet xrs = (XtextResourceSet) rs;

org.eclipse.xpect.ui/src/org/eclipse/xpect/ui/util/XpectUtil.java

@@ -28,6 +28,7 @@
 import org.eclipse.xpect.XpectFile;
 import org.eclipse.xpect.XpectJavaModel;
 import org.eclipse.xpect.runner.XpectRunner;
+import org.eclipse.xpect.runner.XpectTestGlobalState;
 import org.eclipse.xpect.ui.internal.XpectActivator;
 
 import com.google.inject.Injector;
@@ -40,8 +41,8 @@ public static XpectFile loadFile(IFile file) {
 		Injector injector = XpectActivator.getInstance().getInjector(XpectActivator.ORG_ECLIPSE_XPECT_XPECT);
 		XtextResourceSet rs = new XtextResourceSet();
 		IJavaProject javaProject = JavaCore.create(file.getProject());
-		if (XpectRunner.testClassloader != null) {
-			rs.setClasspathURIContext(XpectRunner.testClassloader);
+		if (XpectTestGlobalState.INSTANCE.testClass() != null) {
+			rs.setClasspathURIContext(XpectTestGlobalState.INSTANCE.testClass().getClassLoader());
 			rs.setClasspathUriResolver(new ClassloaderClasspathUriResolver());
 		} else if (javaProject != null && javaProject.exists()) {
 			rs.setClasspathURIContext(javaProject);

org.eclipse.xpect/META-INF/MANIFEST.MF

@@ -19,11 +19,13 @@ Require-Bundle: org.eclipse.xtext,
  org.antlr.runtime;bundle-version="[3.2.0,3.2.1)",
  org.apache.log4j;bundle-version="1.2.24",
  org.junit;bundle-version="4.11.0";visibility:=reexport,
+ junit-jupiter-api;bundle-version="5.9.1";visibility:=reexport,
  org.eclipse.xtext.common.types;visibility:=reexport,
  org.apache.log4j;bundle-version="1.2.0";visibility:=reexport,
  org.objectweb.asm;bundle-version="[9.5.0,10.0.0)";resolution:=optional
 Bundle-RequiredExecutionEnvironment: JavaSE-11
 Export-Package: org.eclipse.xpect,
+ org.eclipse.xpect.dynamic,
  org.eclipse.xpect.expectation,
  org.eclipse.xpect.expectation.impl;
   x-friends:="org.eclipse.xpect.xtext.lib,

org.eclipse.xpect/src/org/eclipse/xpect/dynamic/IXpectDynamicTestFactory.java

@@ -0,0 +1,17 @@
+package org.eclipse.xpect.dynamic;
+
+import java.util.stream.Stream;
+
+import org.eclipse.xpect.XpectImport;
+import org.eclipse.xpect.runner.TestTitleProvider;
+import org.junit.jupiter.api.DynamicNode;
+import org.junit.jupiter.api.TestFactory;
+
+@XpectImport(TestTitleProvider.class)
+public interface IXpectDynamicTestFactory {
+
+	@TestFactory
+	default Stream<DynamicNode> tests() {
+		return XpectDynamicTestFactory.xpectTests(getClass());
+	}
+}

org.eclipse.xpect/src/org/eclipse/xpect/dynamic/XpectDynamicTest.java

@@ -0,0 +1,64 @@
+package org.eclipse.xpect.dynamic;
+
+import java.lang.reflect.InvocationTargetException;
+
+import org.eclipse.xpect.XjmTestMethod;
+import org.eclipse.xpect.runner.ValidatingSetup;
+import org.eclipse.xpect.runner.XpectTestGlobalState;
+import org.eclipse.xpect.setup.ThisTestObject;
+import org.eclipse.xpect.state.Creates;
+import org.eclipse.xpect.state.StateContainer;
+import org.junit.jupiter.api.DynamicTest;
+
+import com.google.common.base.Preconditions;
+
+public class XpectDynamicTest {
+
+	private final String className;
+	private XjmTestMethod method;
+	private final StateContainer state;
+
+	public XpectDynamicTest(StateContainer state, XjmTestMethod method) {
+		Preconditions.checkNotNull(method);
+		this.className = XpectTestGlobalState.INSTANCE.testClass().getName();
+		this.method = method;
+		this.state = state;
+	}
+
+	@Creates
+	public XpectDynamicTest create() {
+		return this;
+	}
+
+	public XjmTestMethod getMethod() {
+		return method;
+	}
+
+	public StateContainer getState() {
+		return state;
+	}
+
+	public DynamicTest test() {
+		String testName = getName();
+		return DynamicTest.dynamicTest(testName, () -> runInternal());
+	}
+
+	public String getName() {
+		String testName = formatDisplayName(method.getName(), className);
+		return testName;
+	}
+
+	protected void runInternal() throws Throwable {
+		Object test = state.get(Object.class, ThisTestObject.class).get();
+		try {
+			method.getJavaMethod().invoke(test);
+		} catch (InvocationTargetException e) {
+			throw e.getCause();
+		}
+	}
+
+	private static String formatDisplayName(String name, String className) {
+		return String.format("%s(%s)", name, className);
+	}
+
+}

org.eclipse.xpect/src/org/eclipse/xpect/dynamic/XpectDynamicTestCase.java

@@ -0,0 +1,174 @@
+package org.eclipse.xpect.dynamic;
+
+import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.xpect.XjmTestMethod;
+import org.eclipse.xpect.XpectFile;
+import org.eclipse.xpect.XpectInvocation;
+import org.eclipse.xpect.XpectJavaModel;
+import org.eclipse.xpect.runner.IXpectURIProvider;
+import org.eclipse.xpect.runner.TestExecutor;
+import org.eclipse.xpect.runner.ValidatingSetup;
+import org.eclipse.xpect.setup.ThisRootTestClass;
+import org.eclipse.xpect.state.Creates;
+import org.eclipse.xpect.state.StateContainer;
+import org.junit.jupiter.api.DynamicTest;
+
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+
+public class XpectDynamicTestCase {
+	private List<DynamicTest> children;
+	private final StateContainer state;
+	private final XpectFile xpectFile;
+
+	public XpectDynamicTestCase(StateContainer state, XpectFile file) {
+		this.xpectFile = file;
+		this.state = state;
+	}
+
+	@Creates
+	public XpectDynamicTestCase create() {
+		return this;
+	}
+
+	/**
+	 * <p>
+	 * To run code before an Xpect test begins, extend this class and annotate the extending class with:
+	 * {@code @org.eclipse.xpect.XpectReplace(org.eclipse.xpect.dynamic.XpectDynamicTestCase)}
+	 * </p>
+	 * <p>
+	 * The extended class must then be included in the values of the annotation of the test case:
+	 * {@code @org.eclipse.xpect.XpectImport({...class})}
+	 * </p>
+	 */
+	public void setUp() throws Throwable {
+		// nothing to set up
+	}
+
+	/**
+	 * <p>
+	 * To run code after an Xpect test finishes, extend this class and annotate the extending class with:
+	 * {@code @org.eclipse.xpect.XpectReplace(org.eclipse.xpect.dynamic.XpectDynamicTestCase)}
+	 * </p>
+	 * <p>
+	 * The extended class must then be included in the values of the annotation of the test case:
+	 * {@code @org.eclipse.xpect.XpectImport({...class})}
+	 * </p>
+	 */
+	public void tearDown() throws Throwable {
+		// nothing to tear down
+	}
+
+	protected List<DynamicTest> createChildren() {
+		List<DynamicTest> tests = Lists.newArrayList();
+		if (xpectFile != null) {
+			/*
+			 * With JUnit 4 runners, we can do setup validation before children run and state clean-up after children are done.
+			 * With JUnit 5 we cannot.
+			 * So the first test does setup validation and the last test does clean-up.
+			 * Meaning their execution times will likely increase notably, when compared to the JUnit 4 reported time.
+			 * Alternatively we can add a first and last test, for setup validation resp. clean-up. This means extra test nodes in the result, as well as extra test results. We then also have the problem of running tests if the setup validation failed.
+			 * XXX: does JUnit 5 offer anything for dynamic tests, to improve this situation?
+			 * As of writing this code, @BeforeEach and @AfterEach are only called before and after the factory method runs.
+			 * We have a factory method with every URL we must run an Xpect test for, as those URLs are known only via an annotation.
+			 */
+			AtomicBoolean setupValidated = new AtomicBoolean(false);
+			AtomicBoolean setupValidationFailed = new AtomicBoolean(false);
+			AtomicInteger finishedChildren = new AtomicInteger(0);
+			XpectJavaModel xjm = xpectFile.getJavaModel();
+			XjmTestMethod[] methods = xjm.getMethods().values().stream().filter(m -> m instanceof XjmTestMethod).toArray(XjmTestMethod[]::new);
+			XpectInvocation[] invocations = Iterables.toArray(xpectFile.getInvocations(), XpectInvocation.class);
+			int childrenCount = methods.length + invocations.length;
+			for (XjmTestMethod method : methods) {
+					DynamicTest test = createDynamicTest(method);
+					tests.add(wrapTest(test, childrenCount, setupValidated, setupValidationFailed, finishedChildren));
+			}
+			for (XpectInvocation inv : invocations) {
+				DynamicTest test = createDynamicTest(inv);
+				tests.add(wrapTest(test, childrenCount, setupValidated, setupValidationFailed, finishedChildren));
+			}
+		}
+		return tests;
+	}
+
+	protected DynamicTest createDynamicTest(XjmTestMethod method) {
+		StateContainer childState = TestExecutor.createState(state, TestExecutor.createTestConfiguration(method));
+		return childState.get(XpectDynamicTest.class).get().test();
+	}
+
+	protected DynamicTest createDynamicTest(XpectInvocation invocation) {
+		StateContainer childState = TestExecutor.createState(state, TestExecutor.createXpectConfiguration(invocation));
+		DynamicTest test = childState.get(XpectInvocationDynamicTest.class).get().test();
+		return test;
+	}
+
+	protected DynamicTest wrapTest(DynamicTest test, final int childrenCount, AtomicBoolean validatedSetup, AtomicBoolean setupValidationFailed, AtomicInteger finishedChildren) {
+		return DynamicTest.dynamicTest(test.getDisplayName(), () -> {
+			try {
+				if (!validatedSetup.getAndSet(true)) {
+					// first test is running, validate setup
+					try {
+						state.get(ValidatingSetup.class).get().validate();
+					} catch (Throwable t) {
+						setupValidationFailed.set(true);
+						throw t;
+					}
+				}
+				if (setupValidationFailed.get()) {
+					throw new AssertionError("Setup validation failed");
+				}
+				try {
+					setUp();
+					test.getExecutable().execute();
+				} finally {
+					tearDown();
+				}
+			} finally {
+				int finished = finishedChildren.incrementAndGet();
+				if (finished >= childrenCount) {
+					// last test is done, do clean-up
+					state.invalidate();
+				}
+			}
+		});
+	}
+
+	protected List<DynamicTest> getChildren() {
+		if (children == null)
+			children = createChildren();
+		return children;
+	}
+
+	public Class<?> getJavaTestClass() {
+		return state.get(Class.class, ThisRootTestClass.class).get();
+	}
+
+	public IXpectURIProvider getURIProvider() {
+		return state.get(IXpectURIProvider.class).get();
+	}
+
+	public StateContainer getState() {
+		return state;
+	}
+
+	public URI getUri() {
+		return xpectFile.eResource().getURI();
+	}
+
+	public XpectFile getXpectFile() {
+		return xpectFile;
+	}
+
+	public String getName() {
+		IXpectURIProvider uriProvider = getURIProvider();
+		URI uri = getUri();
+		URI deresolved = uriProvider.deresolveToProject(uri);
+		String pathInProject = deresolved.trimSegments(1).toString();
+		String fileName = deresolved.lastSegment();
+		return fileName + ": " + pathInProject;
+	}
+}