WIP - initial work towards issue junit-pioneer#348

src/main/java/org/junitpioneer/jupiter/New.java

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+/*
+ * Copyright 2016-2021 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junitpioneer.jupiter;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+// TODO: Consider adding and testing ElementType.FIELD
+@Target(ElementType.PARAMETER)
+public @interface New {
+
+	Class<? extends ResourceFactory<?>> value();
+
+}

src/main/java/org/junitpioneer/jupiter/Resource.java

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+/*
+ * Copyright 2016-2021 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junitpioneer.jupiter;
+
+public interface Resource<T> extends AutoCloseable {
+
+	T get() throws Exception;
+
+	@Override
+	default void close() throws Exception {
+		// no op by default
+	}
+
+}

src/main/java/org/junitpioneer/jupiter/ResourceFactory.java

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+/*
+ * Copyright 2016-2021 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junitpioneer.jupiter;
+
+public interface ResourceFactory<T> extends AutoCloseable {
+
+	Resource<T> create() throws Exception;
+
+	@Override
+	default void close() throws Exception {
+		// no op by default
+	}
+
+}

src/main/java/org/junitpioneer/jupiter/ResourceManagerExtension.java

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+/*
+ * Copyright 2016-2021 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junitpioneer.jupiter;
+
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.api.extension.ParameterContext;
+import org.junit.jupiter.api.extension.ParameterResolutionException;
+import org.junit.jupiter.api.extension.ParameterResolver;
+import org.junit.platform.commons.support.ReflectionSupport;
+
+public class ResourceManagerExtension implements ParameterResolver {
+
+	private static final ExtensionContext.Namespace NAMESPACE = ExtensionContext.Namespace
+			.create(ResourceManagerExtension.class);
+
+	@Override
+	public boolean supportsParameter(ParameterContext parameterContext, ExtensionContext extensionContext)
+			throws ParameterResolutionException {
+		// TODO: Only return true if the parameter is annotated with @New or @Shared
+		// TODO: Check that we're on a test method, rather than say a constructor or a before-each block?
+		// return parameterContext.isAnnotated(New.class);
+		return true;
+	}
+
+	@Override
+	public Object resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext)
+			throws ParameterResolutionException {
+		New newResourceAnnotation = parameterContext
+				.findAnnotation(New.class)
+				.orElseThrow(() -> {
+					// TODO
+					throw new UnsupportedOperationException("TODO");
+				});
+		ResourceFactory<?> resourceFactory = ReflectionSupport.newInstance(newResourceAnnotation.value());
+		// TODO: Put the resourceFactory in the store too?
+		Resource<?> resource;
+		try {
+			resource = resourceFactory.create();
+		}
+		catch (Exception e) {
+			// TODO
+			throw new UnsupportedOperationException("TODO");
+		}
+		// TODO: Check that we're using a custom NAMESPACE
+		extensionContext
+				.getStore(ExtensionContext.Namespace.GLOBAL)
+				.put("theResource", (ExtensionContext.Store.CloseableResource) resource::close);
+		try {
+			return resource.get();
+		}
+		catch (Exception e) {
+			// TODO
+			throw new UnsupportedOperationException("TODO");
+		}
+	}
+
+}

src/main/java/org/junitpioneer/jupiter/TemporaryDirectory.java

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+/*
+ * Copyright 2016-2021 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junitpioneer.jupiter;
+
+import java.io.IOException;
+import java.nio.file.FileVisitResult;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.attribute.BasicFileAttributes;
+
+public class TemporaryDirectory implements ResourceFactory<Path> {
+
+	@Override
+	public Resource<Path> create() throws Exception {
+		return new Resource<Path>() {
+
+			private Path tempDir;
+
+			@Override
+			public Path get() throws Exception {
+				return (tempDir = Files.createTempDirectory(""));
+			}
+
+			@Override
+			public void close() throws Exception {
+				// TODO: Restore file permissions if needed.
+				//       See: https://github.com/junit-team/junit5/issues/2609
+
+				deleteRecursively(tempDir);
+			}
+
+		};
+	}
+
+	@Override
+	public void close() throws Exception {
+		// TODO
+		throw new UnsupportedOperationException("TODO in TemporaryDirectory#close");
+	}
+
+	private void deleteRecursively(Path tempDir) throws IOException {
+		// TODO: See how JUnit 5 recursively deletes temp directories, and if there's anything
+		//       it does that we don't, write unit tests to reproduce their behaviour.
+		Files.walkFileTree(tempDir, new SimpleFileVisitor<Path>() {
+
+			@Override
+			public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
+				// TODO: Can we unit test that we don't throw an exception if
+				//       the dir being deleted doesn't exist anymore due to
+				//       a race condition?
+				Files.delete(file);
+				return FileVisitResult.CONTINUE;
+			}
+
+			@Override
+			public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
+				// TODO: Can we unit test that we don't throw an exception if
+				//       the dir being deleted doesn't exist anymore due to
+				//       a race condition?
+				Files.delete(dir);
+				return FileVisitResult.CONTINUE;
+			}
+
+		});
+	}
+
+}

src/test/java/org/junitpioneer/jupiter/ResourceManagerExtensionTests.java

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+/*
+ * Copyright 2016-2021 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junitpioneer.jupiter;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.MethodOrderer;
+import org.junit.jupiter.api.Order;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.junit.jupiter.api.TestMethodOrder;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+@DisplayName("Resource manager extension")
+@ExtendWith(ResourceManagerExtension.class)
+// TODO: Do we need a test that checks a test case with LifeCycle.PER_METHOD? Ask maintainers.
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
+class ResourceManagerExtensionTests {
+
+	private Path firstRecordedTempDir;
+	private final List<Path> recordedTempDirs = new CopyOnWriteArrayList<>();
+
+	// TODO: Consider adding a constructor with a @New(TemporaryDirectory.class) Path
+
+	@DisplayName("should populate a @New(TemporaryDirectory.class)-annotated parameter with a temp dir resource")
+	@Order(0)
+	@Test
+	void shouldPopulateNewAnnotatedParameterWithTempDirResource(@New(TemporaryDirectory.class) Path tempDir) {
+		assertThat(tempDir).startsWith(Paths.get(System.getProperty("java.io.tmpdir")));
+
+		firstRecordedTempDir = tempDir;
+		recordedTempDirs.add(tempDir);
+	}
+
+	@DisplayName("should tear down the new resource at the end")
+	@Order(1)
+	@Test
+	void shouldTearDownNewResourceAtTheEnd() {
+		assertThat(firstRecordedTempDir).doesNotExist();
+	}
+
+	@DisplayName("should populate a second @New(TemporaryDirectory.class)-annotated parameter with a temp dir resource")
+	@Order(2)
+	@Test
+	void shouldPopulateSecondNewAnnotatedParameterWithTempDirResource(@New(TemporaryDirectory.class) Path tempDir) {
+		assertThat(tempDir).startsWith(Paths.get(System.getProperty("java.io.tmpdir")));
+
+		recordedTempDirs.add(tempDir);
+	}
+
+	@DisplayName("should populate @New(TemporaryDirectory.class)-annotated parameters with writeable temp dirs")
+	@Order(2)
+	@Test
+	void shouldPopulateNewAnnotatedParametersWithWriteableTempDirs(@New(TemporaryDirectory.class) Path tempDir)
+			throws Exception {
+		Files.write(tempDir.resolve("file.txt"), "some random text".getBytes(UTF_8));
+		assertThat(tempDir.resolve("file.txt")).usingCharset(UTF_8).hasContent("some random text");
+
+		recordedTempDirs.add(tempDir);
+	}
+
+	@DisplayName("should have generated new resources each time @New was used")
+	@Order(3)
+	@Test
+	void shouldHaveGeneratedNewResourcesEachTimeNewAnnotationWasUsed() {
+		int numberOfNewTempDirsInThisClass = 3;
+		assertThat(recordedTempDirs).hasSize(numberOfNewTempDirsInThisClass);
+		assertThat(recordedTempDirs.stream().distinct()).hasSize(numberOfNewTempDirsInThisClass);
+	}
+
+	// TODO: Write and test with two custom ResourceFactory implementations: jimfs and OkHttp's MockWebServer
+}