Support File parameters in TempDirectory extension

Resolves: #1725

documentation/src/docs/asciidoc/release-notes/release-notes-5.4.0-RC1.adoc

@@ -70,7 +70,9 @@ repository on GitHub.
   defining result-based callbacks invoked after text execution.
   - See <<../user-guide/index.adoc#extensions-test-result-processing, Test Result
     Processing>> in the User Guide for details.
-
+* `TempDirectory` extension now also accepts to inject a parameter of type `File`.
+  - See <<../user-guide/index.adoc#writing-tests-built-in-extensions-TempDirectory,
+  The TempDirectory Extension>> in the User Guide for details.
 
 [[release-notes-5.4.0-RC1-junit-vintage]]
 === JUnit Vintage

documentation/src/docs/asciidoc/user-guide/writing-tests.adoc

@@ -1656,8 +1656,8 @@ another dependency.
 
 The `TempDirectory` extension can be used to create and clean up a temporary directory
 for an individual test or all tests in a test class. To use it, register the extension
-and add a parameter of type `java.nio.file.Path` annotated with `@TempDir` to your test
-method, lifecycle method, or test class constructor.
+and add a parameter of type `java.nio.file.Path` or `java.io.File` annotated with `@TempDir`
+to your test method, lifecycle method, or test class constructor.
 
 For example, the following test registers the extension for a single test method, creates
 and writes to a file in the temporary directory, and checks its content.
@@ -1681,3 +1681,6 @@ of a custom parent directory of type `Path`. The following example uses the Jimf
 ----
 include::{testDir}/example/TempDirectoryWithCustomFileSystemDemo.java[tags=user_guide]
 ----
+
+WARNING: if you don't use a `FileSystem` relying on the default file system then `File` support
+is not guaranteed.

junit-jupiter-api/src/main/java/org/junit/jupiter/api/support/io/TempDirectory.java

@@ -14,6 +14,7 @@
 import static java.util.stream.Collectors.joining;
 import static org.apiguardian.api.API.Status.EXPERIMENTAL;
 
+import java.io.File;
 import java.io.IOException;
 import java.lang.annotation.Documented;
 import java.lang.annotation.ElementType;
@@ -45,7 +46,8 @@
  *
  * <p>The temporary directory is only created if a test or lifecycle method or
  * test class constructor has a parameter annotated with
- * {@link TempDir @TempDir}. If the parameter type is not {@link Path} or if the
+ * {@link TempDir @TempDir}. If the parameter type is
+ * neither {@link Path} nor {@link File} or if the
  * temporary directory could not be created, this extension will throw a
  * {@link ParameterResolutionException}.
  *
@@ -87,8 +89,8 @@ public final class TempDirectory implements ParameterResolver {
 
 	/**
 	 * {@code TempDir} can be used to annotate a test or lifecycle method or
-	 * test class constructor parameter of type {@link Path} that should be
-	 * resolved into a temporary directory.
+	 * test class constructor parameter of type {@link Path} or {@link File}
+	 * that should be resolved into a temporary directory.
 	 *
 	 * @see TempDirectory
 	 */
@@ -225,15 +227,26 @@ public boolean supportsParameter(ParameterContext parameterContext, ExtensionCon
 	@Override
 	public Object resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext) {
 		Class<?> parameterType = parameterContext.getParameter().getType();
-		if (parameterType != Path.class) {
-			throw new ParameterResolutionException(
-				"Can only resolve parameter of type " + Path.class.getName() + " but was: " + parameterType.getName());
+		boolean expectsPath = parameterType == Path.class;
+		if (!expectsPath && parameterType != File.class) {
+			throw new ParameterResolutionException("Can only resolve parameter of type " + Path.class.getName() + " or "
+					+ File.class.getName() + " but was: " + parameterType.getName());
 		}
-		return extensionContext.getStore(NAMESPACE) //
+		Path path = extensionContext.getStore(NAMESPACE) //
 				.getOrComputeIfAbsent(KEY,
 					key -> tempDirProvider.get(parameterContext, extensionContext, TEMP_DIR_PREFIX),
 					CloseablePath.class) //
 				.get();
+		if (expectsPath) {
+			return path;
+		}
+		try {
+			return path.toFile();
+		}
+		catch (UnsupportedOperationException uoe) { // not default filesystem
+			throw new ParameterResolutionException("Unsupported FileSystem in tempDirProvider: " + tempDirProvider,
+				uoe);
+		}
 	}
 
 	private static CloseablePath createDefaultTempDir(String dirPrefix) {

junit-jupiter-engine/src/test/java/org/junit/jupiter/api/support/io/TempDirectoryTests.java

@@ -11,6 +11,7 @@
 package org.junit.jupiter.api.support.io;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertSame;
@@ -161,13 +162,22 @@ void resolvesTempDirWithCustomParentDirFromProvider() {
 	@DisplayName("reports failure")
 	class Failures {
 
+		@Test
+		@DisplayName("when @TempDir is used on parameter of File type with a custom FileSystem")
+		void onlySupportsParametersOfTypeFileForDefaultFileSystem() {
+			var results = executeTests(selectClass(InvalidFileInjection.class));
+
+			assertSingleFailedTest(results, ParameterResolutionException.class,
+				"Unsupported FileSystem in tempDirProvider: org.junit.jupiter.api.support.io.TempDirectory"/*lambda*/);
+		}
+
 		@Test
 		@DisplayName("when @TempDir is used on parameter of wrong type")
-		void onlySupportsParametersOfTypePath() {
+		void onlySupportsParametersOfTypePathAndFile() {
 			var results = executeTests(selectClass(InvalidTestCase.class));
 
 			assertSingleFailedTest(results, ParameterResolutionException.class,
-				"Can only resolve parameter of type java.nio.file.Path");
+				"Can only resolve parameter of type java.nio.file.Path or java.io.File");
 		}
 
 		@Test
@@ -352,7 +362,46 @@ static class SeparateTempDirsWhenUsedOnForEachLifecycleMethodsWithTestInstancePe
 	@ExtendWith(TempDirectory.class)
 	static class InvalidTestCase {
 		@Test
-		void wrongParameterType(@SuppressWarnings("unused") @TempDir File ignored) {
+		void wrongParameterType(@SuppressWarnings("unused") @TempDir String ignored) {
+			fail("this should never be called");
+		}
+	}
+
+	@Nested
+	@DisplayName("User can rely on java.io.File injection type")
+	@ExtendWith(TempDirectory.class)
+	class FileInjection {
+		@Test
+		@DisplayName("File and Path injections lead to the same folder/behavior")
+		void checkFile(@TempDir File tempDir, @TempDir Path ref) {
+			Path path = tempDir.toPath();
+			assertEquals(ref.toAbsolutePath(), path.toAbsolutePath());
+			assertTrue(Files.exists(path));
+		}
+	}
+
+	@DisplayName("User can't rely on java.io.File injection type for custom filesystems")
+	static class InvalidFileInjection {
+		private FileSystem fileSystem;
+
+		@BeforeEach
+		void createFileSystem() {
+			fileSystem = Jimfs.newFileSystem();
+		}
+
+		@AfterEach
+		void closeFileSystem() throws Exception {
+			fileSystem.close();
+		}
+
+		@RegisterExtension
+		@SuppressWarnings("unused")
+		Extension tempDirectory = TempDirectory.createInCustomDirectory(
+			() -> Files.createDirectories(fileSystem.getPath("tmp")));
+
+		@Test
+		@DisplayName("File can't be injected using Jimfs FileSystem")
+		void failingInjection(@TempDir File tempDir) {
 			fail("this should never be called");
 		}
 	}