Let @TempDir fail fast with File annotated element and non-defaul…

…t file system temp directory (#3921)

Closes #3910.

---------

Co-authored-by: Marc Philipp <[email protected]>

documentation/src/docs/asciidoc/release-notes/release-notes-5.11.0.adoc

@@ -183,6 +183,9 @@ on GitHub.
   tests, in particular in recent versions of Java that support records.
 * `@TempDir` now fails fast in case `TempDirFactory::createTempDirectory` returns
   `null`, a file, or a symbolic link to a file.
+* `@TempDir` now fails fast in case the annotated target is of type `File` and
+  `TempDirFactory::createTempDirectory` returns a `Path` that does not belong to the
+  default file system.
 
 
 [[release-notes-5.11.0-junit-vintage]]

junit-jupiter-api/src/main/java/org/junit/jupiter/api/io/TempDir.java

@@ -40,11 +40,24 @@
  *
  * <p>The temporary directory is only created if a field in a test class or a
  * parameter in a lifecycle method or test method is annotated with
- * {@code @TempDir}. If the field type or parameter type is neither {@link Path}
- * nor {@link File}, if a field is declared as {@code final}, or if the temporary
- * directory cannot be created, an {@link ExtensionConfigurationException} or a
- * {@link ParameterResolutionException} will be thrown as appropriate. In
- * addition, a {@code ParameterResolutionException} will be thrown for a
+ * {@code @TempDir}.
+ * An {@link ExtensionConfigurationException} or a
+ * {@link ParameterResolutionException} will be thrown in one of the following
+ * cases:
+ *
+ * <ul>
+ * <li>If the field type or parameter type is neither {@link Path} nor
+       {@link File}.</li>
+ * <li>If a field is declared as {@code final}.</li>
+ * <li>If the temporary directory cannot be created.</li>
+ * <li>If the field type or parameter type is {@code File} and a custom
+ *     {@linkplain TempDir#factory() factory} is used, which creates a temporary
+ *     directory that does not belong to the
+ *     {@linkplain java.nio.file.FileSystems#getDefault() default file system}.
+ * </li>
+ * </ul>
+ *
+ * In addition, a {@code ParameterResolutionException} will be thrown for a
  * constructor parameter annotated with {@code @TempDir}.
  *
  * <h2>Scope</h2>

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/extension/TempDirectory.java

@@ -26,6 +26,7 @@
 import java.lang.reflect.Field;
 import java.lang.reflect.Parameter;
 import java.nio.file.DirectoryNotEmptyException;
+import java.nio.file.FileSystems;
 import java.nio.file.FileVisitResult;
 import java.nio.file.Files;
 import java.nio.file.NoSuchFileException;
@@ -145,7 +146,7 @@ private void injectFields(ExtensionContext context, Object testInstance, Class<?
 				CleanupMode cleanupMode = determineCleanupModeForField(field);
 				TempDirFactory factory = determineTempDirFactoryForField(field, scope);
 				makeAccessible(field).set(testInstance,
-					getPathOrFile(new FieldContext(field), field.getType(), factory, cleanupMode, scope, context));
+					getPathOrFile(field.getType(), new FieldContext(field), factory, cleanupMode, scope, context));
 			}
 			catch (Throwable t) {
 				throw ExceptionUtils.throwAsUncheckedException(t);
@@ -178,7 +179,7 @@ public Object resolveParameter(ParameterContext parameterContext, ExtensionConte
 		CleanupMode cleanupMode = determineCleanupModeForParameter(parameterContext);
 		Scope scope = getScope(extensionContext);
 		TempDirFactory factory = determineTempDirFactoryForParameter(parameterContext, scope);
-		return getPathOrFile(parameterContext, parameterType, factory, cleanupMode, scope, extensionContext);
+		return getPathOrFile(parameterType, parameterContext, factory, cleanupMode, scope, extensionContext);
 	}
 
 	private CleanupMode determineCleanupModeForField(Field field) {
@@ -248,23 +249,24 @@ private void assertSupportedType(String target, Class<?> type) {
 		}
 	}
 
-	private Object getPathOrFile(AnnotatedElementContext elementContext, Class<?> type, TempDirFactory factory,
+	private Object getPathOrFile(Class<?> elementType, AnnotatedElementContext elementContext, TempDirFactory factory,
 			CleanupMode cleanupMode, Scope scope, ExtensionContext extensionContext) {
 		Namespace namespace = scope == Scope.PER_DECLARATION //
 				? NAMESPACE.append(elementContext) //
 				: NAMESPACE;
 		Path path = extensionContext.getStore(namespace) //
-				.getOrComputeIfAbsent(KEY, __ -> createTempDir(factory, cleanupMode, elementContext, extensionContext),
+				.getOrComputeIfAbsent(KEY,
+					__ -> createTempDir(factory, cleanupMode, elementType, elementContext, extensionContext),
 					CloseablePath.class) //
 				.get();
 
-		return (type == Path.class) ? path : path.toFile();
+		return (elementType == Path.class) ? path : path.toFile();
 	}
 
-	static CloseablePath createTempDir(TempDirFactory factory, CleanupMode cleanupMode,
+	static CloseablePath createTempDir(TempDirFactory factory, CleanupMode cleanupMode, Class<?> elementType,
 			AnnotatedElementContext elementContext, ExtensionContext extensionContext) {
 		try {
-			return new CloseablePath(factory, cleanupMode, elementContext, extensionContext);
+			return new CloseablePath(factory, cleanupMode, elementType, elementContext, extensionContext);
 		}
 		catch (Exception ex) {
 			throw new ExtensionConfigurationException("Failed to create default temp directory", ex);
@@ -285,8 +287,8 @@ static class CloseablePath implements CloseableResource {
 		private final CleanupMode cleanupMode;
 		private final ExtensionContext extensionContext;
 
-		private CloseablePath(TempDirFactory factory, CleanupMode cleanupMode, AnnotatedElementContext elementContext,
-				ExtensionContext extensionContext) throws Exception {
+		private CloseablePath(TempDirFactory factory, CleanupMode cleanupMode, Class<?> elementType,
+				AnnotatedElementContext elementContext, ExtensionContext extensionContext) throws Exception {
 			this.dir = factory.createTempDirectory(elementContext, extensionContext);
 			this.factory = factory;
 			this.cleanupMode = cleanupMode;
@@ -296,6 +298,13 @@ private CloseablePath(TempDirFactory factory, CleanupMode cleanupMode, Annotated
 				close();
 				throw new PreconditionViolationException("temp directory must be a directory");
 			}
+
+			if (elementType == File.class && !dir.getFileSystem().equals(FileSystems.getDefault())) {
+				close();
+				throw new PreconditionViolationException(
+					"temp directory with non-default file system cannot be injected into " + File.class.getName()
+							+ " target");
+			}
 		}
 
 		Path get() {