Bug 56491 [Tasks] DeleteCompletedTasks requires Markers to be refreshed
3.0 M8 If you create a new user defined task and mark it completed by clicking on the first column or by using the context menu, the delete completed task actino does not pick up the completed task. However it does work after the markers have been refreshed (eg project rebuild). to test: 1. create a user defined marker, ensuring it is not created as completed 2. click on the first column to mark it as complete 3. select delete completed tasks from the context menu, notice it doesn't pick up the task 4. perform a project re-build (Project|clean...) 5. repeat step 3, it now picks up the marker as complete It looks like the underlying IMarker is being updated, but the concrete TaskMarker is not. The action is looking at the concrete markers.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/internal/MarkerView.java
protected void updateStatusMessage() {
		ISelection selection = getViewer().getSelection();
		
		if (selection instanceof IStructuredSelection)
			updateStatusMessage((IStructuredSelection) selection);
		else 
			updateStatusMessage(null);
	}
	/**
	 * Updates that message displayed in the status line.  If the
	 * selection parameter is <code>null</code> or its size is 0, the status 
	 * area is blanked out.  If only 1 marker is selected, the
	 * status area is updated with the contents of the message
	 * attribute of this marker.  In other cases (more than one marker
	 * is selected) the status area indicates how many items have
	 * been selected.
	 * <p>
	 * This method may be overwritten.
	 * </p><p>
	 * This method is called whenever a selection changes in this view.
	 * </p>
	 * @param selection a valid selection or <code>null</code>
	 */
	protected void updateStatusMessage(IStructuredSelection selection) {
		String message = ""; 
		
		if (selection == null || selection.size() == 0){
			
			message = updateSummaryVisible();
		} else if (selection.size() == 1) {