Prompt user when switching to a locked workspace in Eclipse

Prompts user on attempting to switch to a workspace that is currently
locked by another Eclipse instance, a prompt dialog is now shown
informing the user about the lock and preventing Eclipse from exiting

Author: SougandhS

bundles/org.eclipse.ui.workbench/eclipseui/org/eclipse/ui/internal/Workbench.java

@@ -35,9 +35,12 @@
 import java.io.InputStream;
 import java.io.StringReader;
 import java.io.StringWriter;
+import java.net.MalformedURLException;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -80,6 +83,7 @@
 import org.eclipse.core.runtime.SafeRunner;
 import org.eclipse.core.runtime.Status;
 import org.eclipse.core.runtime.SubMonitor;
+import org.eclipse.core.runtime.URIUtil;
 import org.eclipse.core.runtime.dynamichelpers.IExtensionTracker;
 import org.eclipse.core.runtime.jobs.Job;
 import org.eclipse.core.runtime.preferences.ConfigurationScope;
@@ -114,6 +118,7 @@
 import org.eclipse.e4.ui.workbench.modeling.EModelService;
 import org.eclipse.e4.ui.workbench.modeling.EPartService;
 import org.eclipse.e4.ui.workbench.modeling.ISaveHandler;
+import org.eclipse.e4.ui.workbench.swt.internal.copy.WorkbenchSWTMessages;
 import org.eclipse.emf.ecore.EObject;
 import org.eclipse.emf.ecore.resource.Resource;
 import org.eclipse.emf.ecore.util.EcoreUtil;
@@ -2699,7 +2704,8 @@ private static String buildCommandLine(String workspace) {
 	 * as the workspace location.
 	 *
 	 * @param workspacePath the new workspace location
-	 * @return {@link IApplication#EXIT_OK} or {@link IApplication#EXIT_RELAUNCH}
+	 * @return {@link IApplication#EXIT_OK} or {@link IApplication#EXIT_RELAUNCH} or
+	 *         <code>null</code>
 	 */
 	@SuppressWarnings("restriction")
 	public static Object setRestartArguments(String workspacePath) {
@@ -2714,12 +2720,56 @@ public static Object setRestartArguments(String workspacePath) {
 		if (command_line == null) {
 			return IApplication.EXIT_OK;
 		}
+		Path selectedWorkspace = Path.of(workspacePath);
+		try {
+			if (isWorkspaceLocked(selectedWorkspace.toUri().toURL())) {
+				MessageDialog.openError(PlatformUI.getWorkbench().getActiveWorkbenchWindow().getShell(),
+						WorkbenchSWTMessages.IDEApplication_workspaceCannotLockTitle,
+						WorkbenchSWTMessages.IDEApplication_workspaceCannotLockMessage);
+				return null;
+			}
+		} catch (MalformedURLException e) {
+			return null;
+		}
 
 		System.setProperty(Workbench.PROP_EXIT_CODE, IApplication.EXIT_RELAUNCH.toString());
 		System.setProperty(IApplicationContext.EXIT_DATA_PROPERTY, command_line);
 		return IApplication.EXIT_RELAUNCH;
 	}
 
+	/**
+	 * Check if the selected workspace is already being used by another eclipse
+	 * application
+	 *
+	 * @param workspaceUrl the <code>URL</code> of selected workspace
+	 * @return <code>true</code> if workspace is used, <code>false</code> if not
+	 *         used.
+	 */
+	private static boolean isWorkspaceLocked(URL workspaceUrl) {
+		Path lockFile = getLockInfoFile(workspaceUrl);
+		if (lockFile != null && Files.exists(lockFile)) {
+			return true;
+		}
+		return false;
+	}
+
+	/**
+	 * Returns the lock file.
+	 *
+	 * @param workspaceUrl the <code>URL</code> of selected workspace
+	 * @return the path to the <code>.lock_info</code> file within the specified
+	 *         workspace, or <code> null</code> if the workspace URL cannot be
+	 *         converted to a valid URI
+	 */
+	private static Path getLockInfoFile(URL workspaceUrl) {
+		Path lockFile = Path.of(".metadata", ".lock_info"); //$NON-NLS-1$ //$NON-NLS-2$
+		try {
+			return Path.of(URIUtil.toURI(workspaceUrl)).resolve(lockFile);
+		} catch (URISyntaxException e) {
+			return null;
+		}
+	}
+
 	/**
 	 * Returns the ids of all plug-ins that extend the
 	 * <code>org.eclipse.ui.startup</code> extension point.