StatusLineManager: improve error with callstack

eclipse-jdt/eclipse.jdt.ui#61

Author: jukzi

bundles/org.eclipse.jface/src/org/eclipse/jface/action/IStatusLineManager.java

@@ -33,7 +33,8 @@ public interface IStatusLineManager extends IContributionManager {
 	/**
 	 * Creates a new progress monitor which reports progress in the status line.
 	 * Note that the returned progress monitor may only be accessed from the UI
-	 * thread.
+	 * thread. Reusing the monitor requires to finally call progressMonitor.done()
+	 * before using it again.
 	 *
 	 * @return the progress monitor
 	 *

bundles/org.eclipse.jface/src/org/eclipse/jface/action/StatusLineManager.java

@@ -149,14 +149,17 @@ public IProgressMonitor getProgressMonitor() {
 				: new NullProgressMonitor();
 
 		return new IProgressMonitor() {
-			private volatile boolean taskStarted;
+			private volatile Exception taskStarted;
 
 			@Override
 			public void beginTask(String name, int totalWork) {
-				if (taskStarted) {
-					throw new IllegalStateException("beginTask must only be called once per instance"); //$NON-NLS-1$
+				if (taskStarted != null) {
+					throw new IllegalStateException(
+							"beginTask should only be called once per instance. At least call done() before further invocations", //$NON-NLS-1$
+							taskStarted);
 				}
-				taskStarted = true;
+				taskStarted = new IllegalStateException(
+						"beginTask(" + name + ", " + totalWork + ") was called here previously"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
 				// According to the IProgressMonitor javadoc beginTask() must only be called
 				// once on a given progress monitor instance.
 				// However it works in this case multiple times if done() was called in between.
@@ -165,13 +168,13 @@ public void beginTask(String name, int totalWork) {
 
 			@Override
 			public void done() {
-				if (!taskStarted) {
+				if (taskStarted == null) {
 					// ignore call to done() if beginTask() was not called!
 					// Otherwise an otherwise already started delegate would be finished
 					// see https://github.com/eclipse-jdt/eclipse.jdt.ui/issues/61
 					return;
 				}
-				taskStarted = false;
+				taskStarted = null;
 				progressDelegate.done();
 			}
 
@@ -196,7 +199,7 @@ public void setCanceled(boolean value) {
 
 			@Override
 			public void setTaskName(String name) {
-				if (!taskStarted) {
+				if (taskStarted == null) {
 					throw new IllegalStateException("call to beginTask() missing"); //$NON-NLS-1$
 				}
 				progressDelegate.setTaskName(name);
@@ -211,7 +214,7 @@ public void subTask(String name) {
 
 			@Override
 			public void worked(int work) {
-				if (!taskStarted) {
+				if (taskStarted == null) {
 					throw new IllegalStateException("call to beginTask() missing"); //$NON-NLS-1$
 				}
 				progressDelegate.worked(work);