Avoid failing test because temporary directory cannot be deleted

On Windows the temporary directory sometimes cannot be deleted because
the files are still locked and you get an error like:

The process cannot access the file because it is being used by another process

This change allows the deletion of the temp directory to fail without
failing the whole test. In case the temp dir can't be deleted a warning
is printed on System.err

Fixes #2568

Author: jonahgraham

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_dnd_Clipboard.java

@@ -18,10 +18,14 @@
 import static org.junit.jupiter.api.Assumptions.assumeTrue;
 
 import java.io.BufferedReader;
+import java.io.IOException;
 import java.io.InputStreamReader;
 import java.lang.ProcessBuilder.Redirect;
+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;
 import java.rmi.NotBoundException;
 import java.rmi.RemoteException;
 import java.rmi.registry.LocateRegistry;
@@ -40,7 +44,6 @@
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.RepeatedTest;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.io.TempDir;
 
 import clipboard.ClipboardCommands;
 
@@ -54,8 +57,6 @@
 public class Test_org_eclipse_swt_dnd_Clipboard {
 
 	private static final int DEFAULT_TIMEOUT_MS = 10000;
-	@TempDir
-	static Path tempFolder;
 	static int uniqueId = 1;
 	private Display display;
 	private Shell shell;
@@ -64,6 +65,7 @@ public class Test_org_eclipse_swt_dnd_Clipboard {
 	private RTFTransfer rtfTransfer;
 	private ClipboardCommands remote;
 	private Process remoteClipboardProcess;
+	private Path remoteClipboardTempDir;
 
 	@BeforeEach
 	public void setUp() {
@@ -139,21 +141,24 @@ private void startRemoteClipboardCommands() throws Exception {
 		 * If the ClipboardTest starts to get more complicated, or other tests want to
 		 * replicate this design element, then refactoring this is an option.
 		 */
+		remoteClipboardTempDir = Files.createTempDirectory("swt-test-Clipboard");
 		List.of( //
 				"ClipboardTest", //
 				"ClipboardCommands", //
 				"ClipboardCommandsImpl", //
 				"ClipboardTest$LocalHostOnlySocketFactory" //
 		).forEach((f) -> {
 			// extract the files and put them in the temp directory
-			SwtTestUtil.getPath("/clipboard/" + f + ".class", tempFolder.resolve("clipboard/" + f + ".class"));
+			SwtTestUtil.getPath("/clipboard/" + f + ".class",
+					remoteClipboardTempDir.resolve("clipboard/" + f + ".class"));
 		});
 
 		String javaHome = System.getProperty("java.home");
 		String javaExe = javaHome + "/bin/java" + (SwtTestUtil.isWindowsOS ? ".exe" : "");
 		assertTrue(Files.exists(Path.of(javaExe)));
 
-		ProcessBuilder pb = new ProcessBuilder(javaExe, "clipboard.ClipboardTest").directory(tempFolder.toFile());
+		ProcessBuilder pb = new ProcessBuilder(javaExe, "clipboard.ClipboardTest")
+				.directory(remoteClipboardTempDir.toFile());
 		pb.inheritIO();
 		pb.redirectOutput(Redirect.PIPE);
 		remoteClipboardProcess = pb.start();
@@ -213,6 +218,41 @@ private void startRemoteClipboardCommands() throws Exception {
 	}
 
 	private void stopRemoteClipboardCommands() throws Exception {
+		try {
+			stopRemoteProcess();
+		} finally {
+			deleteRemoteTempDir();
+		}
+	}
+
+	private void deleteRemoteTempDir() {
+		if (remoteClipboardTempDir != null) {
+			// At this point the process is ideally destroyed - or at least the test will
+			// report a failure if it isn't. Clean up the extracted files, but don't
+			// fail test if we fail to delete
+			try {
+				Files.walkFileTree(remoteClipboardTempDir, new SimpleFileVisitor<Path>() {
+					@Override
+					public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
+						Files.delete(file);
+						return FileVisitResult.CONTINUE;
+					}
+
+					@Override
+					public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
+						Files.delete(dir);
+						return FileVisitResult.CONTINUE;
+					}
+				});
+			} catch (IOException e) {
+				System.err.println("SWT Warning: Failed to clean up temp directory " + remoteClipboardTempDir
+						+ " Error:" + e.toString());
+				e.printStackTrace();
+			}
+		}
+	}
+
+	private void stopRemoteProcess() throws RemoteException, InterruptedException {
 		try {
 			if (remote != null) {
 				remote.stop();