Allow garbage collecting executed runners

RunnerTestDescriptors can now be garbage collected after they have been
executed because they are now removed from the list of children of the
engine descriptor.

junit-vintage-engine/src/main/java/org/junit/vintage/engine/VintageTestEngine.java

@@ -14,6 +14,7 @@
 import static org.junit.platform.engine.TestExecutionResult.successful;
 import static org.junit.vintage.engine.descriptor.VintageTestDescriptor.ENGINE_ID;
 
+import java.util.Iterator;
 import java.util.Optional;
 
 import org.apiguardian.api.API;
@@ -68,19 +69,17 @@ public void execute(ExecutionRequest request) {
 		EngineExecutionListener engineExecutionListener = request.getEngineExecutionListener();
 		VintageEngineDescriptor engineDescriptor = (VintageEngineDescriptor) request.getRootTestDescriptor();
 		engineExecutionListener.executionStarted(engineDescriptor);
-		RunnerExecutor runnerExecutor = new RunnerExecutor(engineExecutionListener,
-			engineDescriptor.getTestSourceProvider());
-		executeAllChildren(runnerExecutor, engineDescriptor);
+		executeAllChildren(engineDescriptor, engineExecutionListener);
 		engineExecutionListener.executionFinished(engineDescriptor, successful());
 	}
 
-	private void executeAllChildren(RunnerExecutor runnerExecutor, TestDescriptor engineDescriptor) {
-		// @formatter:off
-		engineDescriptor.getChildren()
-				.stream()
-				.map(RunnerTestDescriptor.class::cast)
-				.forEach(runnerExecutor::execute);
-		// @formatter:on
+	private void executeAllChildren(VintageEngineDescriptor engineDescriptor,
+			EngineExecutionListener engineExecutionListener) {
+		RunnerExecutor runnerExecutor = new RunnerExecutor(engineExecutionListener);
+		for (Iterator<TestDescriptor> iterator = engineDescriptor.getModifiableChildren().iterator(); iterator.hasNext();) {
+			runnerExecutor.execute((RunnerTestDescriptor) iterator.next());
+			iterator.remove();
+		}
 	}
 
 }

junit-vintage-engine/src/main/java/org/junit/vintage/engine/descriptor/VintageEngineDescriptor.java

@@ -12,7 +12,10 @@
 
 import static org.apiguardian.api.API.Status.INTERNAL;
 
+import java.util.Set;
+
 import org.apiguardian.api.API;
+import org.junit.platform.engine.TestDescriptor;
 import org.junit.platform.engine.UniqueId;
 import org.junit.platform.engine.support.descriptor.EngineDescriptor;
 
@@ -22,15 +25,12 @@
 @API(status = INTERNAL, since = "5.6")
 public class VintageEngineDescriptor extends EngineDescriptor {
 
-	private final TestSourceProvider testSourceProvider;
-
-	public VintageEngineDescriptor(UniqueId uniqueId, TestSourceProvider testSourceProvider) {
+	public VintageEngineDescriptor(UniqueId uniqueId) {
 		super(uniqueId, "JUnit Vintage");
-		this.testSourceProvider = testSourceProvider;
 	}
 
-	public TestSourceProvider getTestSourceProvider() {
-		return testSourceProvider;
+	public Set<TestDescriptor> getModifiableChildren() {
+		return children;
 	}
 
 }

junit-vintage-engine/src/main/java/org/junit/vintage/engine/discovery/RunnerTestDescriptorPostProcessor.java

@@ -35,11 +35,7 @@ class RunnerTestDescriptorPostProcessor {
 
 	private final UniqueIdReader uniqueIdReader = new UniqueIdReader();
 	private final UniqueIdStringifier uniqueIdStringifier = new UniqueIdStringifier();
-	private final TestSourceProvider testSourceProvider;
-
-	public RunnerTestDescriptorPostProcessor(TestSourceProvider testSourceProvider) {
-		this.testSourceProvider = testSourceProvider;
-	}
+	private final TestSourceProvider testSourceProvider = new TestSourceProvider();
 
 	void applyFiltersAndCreateDescendants(RunnerTestDescriptor runnerTestDescriptor) {
 		addChildrenRecursively(runnerTestDescriptor);

junit-vintage-engine/src/main/java/org/junit/vintage/engine/discovery/VintageDiscoverer.java

@@ -19,7 +19,6 @@
 import org.junit.platform.engine.UniqueId;
 import org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolver;
 import org.junit.vintage.engine.descriptor.RunnerTestDescriptor;
-import org.junit.vintage.engine.descriptor.TestSourceProvider;
 import org.junit.vintage.engine.descriptor.VintageEngineDescriptor;
 
 /**
@@ -39,16 +38,13 @@ public class VintageDiscoverer {
 	// @formatter:on
 
 	public VintageEngineDescriptor discover(EngineDiscoveryRequest discoveryRequest, UniqueId uniqueId) {
-		TestSourceProvider testSourceProvider = new TestSourceProvider();
-		VintageEngineDescriptor engineDescriptor = new VintageEngineDescriptor(uniqueId, testSourceProvider);
+		VintageEngineDescriptor engineDescriptor = new VintageEngineDescriptor(uniqueId);
 		resolver.resolve(discoveryRequest, engineDescriptor);
-		RunnerTestDescriptorPostProcessor postProcessor = new RunnerTestDescriptorPostProcessor(testSourceProvider);
-		// @formatter:off
-		engineDescriptor.getChildren().stream()
-				.filter(RunnerTestDescriptor.class::isInstance)
-				.map(RunnerTestDescriptor.class::cast)
-				.forEach(postProcessor::applyFiltersAndCreateDescendants);
-		// @formatter:on
+		RunnerTestDescriptorPostProcessor postProcessor = new RunnerTestDescriptorPostProcessor();
+		for (TestDescriptor testDescriptor : engineDescriptor.getChildren()) {
+			RunnerTestDescriptor runnerTestDescriptor = (RunnerTestDescriptor) testDescriptor;
+			postProcessor.applyFiltersAndCreateDescendants(runnerTestDescriptor);
+		}
 		return engineDescriptor;
 	}
 

junit-vintage-engine/src/main/java/org/junit/vintage/engine/execution/RunnerExecutor.java

@@ -28,11 +28,10 @@
 public class RunnerExecutor {
 
 	private final EngineExecutionListener engineExecutionListener;
-	private final TestSourceProvider testSourceProvider;
+	private final TestSourceProvider testSourceProvider = new TestSourceProvider();
 
-	public RunnerExecutor(EngineExecutionListener engineExecutionListener, TestSourceProvider testSourceProvider) {
+	public RunnerExecutor(EngineExecutionListener engineExecutionListener) {
 		this.engineExecutionListener = engineExecutionListener;
-		this.testSourceProvider = testSourceProvider;
 	}
 
 	public void execute(RunnerTestDescriptor runnerTestDescriptor) {

junit-vintage-engine/src/test/java/org/junit/vintage/engine/discovery/RunnerTestDescriptorPostProcessorTests.java

@@ -28,7 +28,6 @@
 import org.junit.platform.launcher.core.LauncherDiscoveryRequestBuilder;
 import org.junit.vintage.engine.VintageUniqueIdBuilder;
 import org.junit.vintage.engine.descriptor.RunnerTestDescriptor;
-import org.junit.vintage.engine.descriptor.TestSourceProvider;
 import org.junit.vintage.engine.samples.junit4.IgnoredJUnit4TestCase;
 import org.junit.vintage.engine.samples.junit4.IgnoredJUnit4TestCaseWithNotFilterableRunner;
 import org.junit.vintage.engine.samples.junit4.NotFilterableRunner;
@@ -75,8 +74,7 @@ private void resolve(DiscoverySelector selector) {
 			mock(LauncherDiscoveryListener.class)).build();
 		TestDescriptor engineDescriptor = new VintageDiscoverer().discover(request, VintageUniqueIdBuilder.engineId());
 		var runnerTestDescriptor = (RunnerTestDescriptor) getOnlyElement(engineDescriptor.getChildren());
-		new RunnerTestDescriptorPostProcessor(new TestSourceProvider()).applyFiltersAndCreateDescendants(
-			runnerTestDescriptor);
+		new RunnerTestDescriptorPostProcessor().applyFiltersAndCreateDescendants(runnerTestDescriptor);
 	}
 
 }