Make ExtensionContextSupplier a functional interface

To allow simple constant lambda implementations

Author: marcphilipp

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/ClassBasedTestDescriptor.java

@@ -287,7 +287,7 @@ private TestInstances instantiateAndPostProcessTestInstance(JupiterEngineExecuti
 			ClassExtensionContext ourExtensionContext, ExtensionRegistry registry,
 			JupiterEngineExecutionContext context) {
 
-		ExtensionContextSupplier extensionContext = new ExtensionContextSupplier(context.getExtensionContext(),
+		ExtensionContextSupplier extensionContext = ExtensionContextSupplier.create(context.getExtensionContext(),
 			ourExtensionContext);
 		TestInstances instances = instantiateTestClass(parentExecutionContext, extensionContext, registry, context);
 		context.getThrowableCollector().execute(() -> {

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/execution/ExtensionContextSupplier.java

@@ -24,28 +24,38 @@
  * @since 5.12
  * @see TestClassInstanceConstructionParticipatingExtension
  */
+@FunctionalInterface
 @API(status = INTERNAL, since = "5.12")
-public final class ExtensionContextSupplier {
+public interface ExtensionContextSupplier {
 
-	private final ExtensionContext currentExtensionContext;
-	private final ExtensionContext legacyExtensionContext;
-
-	public ExtensionContextSupplier(ExtensionContext currentExtensionContext, ExtensionContext legacyExtensionContext) {
-		this.currentExtensionContext = currentExtensionContext;
-		this.legacyExtensionContext = legacyExtensionContext;
+	static ExtensionContextSupplier create(ExtensionContext currentExtensionContext,
+			ExtensionContext legacyExtensionContext) {
+		if (currentExtensionContext == legacyExtensionContext) {
+			return __ -> currentExtensionContext;
+		}
+		return new ScopeBasedExtensionContextSupplier(currentExtensionContext, legacyExtensionContext);
 	}
 
-	public ExtensionContext get(TestClassInstanceConstructionParticipatingExtension extension) {
-		if (currentExtensionContext == legacyExtensionContext || isTestScoped(extension)) {
-			return currentExtensionContext;
+	ExtensionContext get(TestClassInstanceConstructionParticipatingExtension extension);
+
+	class ScopeBasedExtensionContextSupplier implements ExtensionContextSupplier {
+
+		private final ExtensionContext currentExtensionContext;
+		private final ExtensionContext legacyExtensionContext;
+
+		private ScopeBasedExtensionContextSupplier(ExtensionContext currentExtensionContext,
+				ExtensionContext legacyExtensionContext) {
+			this.currentExtensionContext = currentExtensionContext;
+			this.legacyExtensionContext = legacyExtensionContext;
 		}
-		else {
-			return legacyExtensionContext;
+
+		public ExtensionContext get(TestClassInstanceConstructionParticipatingExtension extension) {
+			return isTestScoped(extension) ? currentExtensionContext : legacyExtensionContext;
 		}
-	}
 
-	private boolean isTestScoped(TestClassInstanceConstructionParticipatingExtension extension) {
-		ExtensionContext rootContext = currentExtensionContext.getRoot();
-		return extension.getExtensionContextScopeDuringTestClassInstanceConstruction(rootContext) == TEST_METHOD;
+		private boolean isTestScoped(TestClassInstanceConstructionParticipatingExtension extension) {
+			ExtensionContext rootContext = legacyExtensionContext.getRoot();
+			return extension.getExtensionContextScopeDuringTestClassInstanceConstruction(rootContext) == TEST_METHOD;
+		}
 	}
 }

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/execution/ParameterResolutionUtils.java

@@ -83,8 +83,7 @@ public static Object[] resolveParameters(Method method, Optional<Object> target,
 	 */
 	public static Object[] resolveParameters(Executable executable, Optional<Object> target,
 			Optional<Object> outerInstance, ExtensionContext extensionContext, ExtensionRegistry extensionRegistry) {
-		ExtensionContextSupplier context = new ExtensionContextSupplier(extensionContext, extensionContext);
-		return resolveParameters(executable, target, outerInstance, context, extensionRegistry);
+		return resolveParameters(executable, target, outerInstance, __ -> extensionContext, extensionRegistry);
 	}
 
 	public static Object[] resolveParameters(Executable executable, Optional<Object> target,

jupiter-tests/src/test/java/org/junit/jupiter/engine/execution/InterceptingExecutableInvokerTests.java

@@ -31,7 +31,7 @@ void invokeMethod() {
 
 	@Override
 	<T> T invokeConstructor(Constructor<T> constructor, Object outerInstance) {
-		ExtensionContextSupplier context = new ExtensionContextSupplier(extensionContext, extensionContext);
+		ExtensionContextSupplier context = ExtensionContextSupplier.create(extensionContext, extensionContext);
 		return newInvoker().invoke(constructor, Optional.ofNullable(outerInstance), context, extensionRegistry,
 			passthroughInterceptor());
 	}