Bug 64372 Projects showing up in Package Explorer twice [package explorer]
20040527-0800 When I load the platform-ui module and org.eclipse.tests from HEAD org.eclipse.tests is showing up twice in the PackageExplorer. This is not a a problem in the Resource Navigator. Open type only shows it once so it doesn't look like there are two instance in the workspace
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
object = filter(object, parent, filters);
					if (object != null) {
						list.add(object);
					}
				} else
					list.add(object);
			}
			return list.toArray();
		}
		/*
		 * @see AbstractTreeViewer#isExpandable(java.lang.Object)
		 */
		public boolean isExpandable(Object parent) {
			if (isFlatLayout())
				return super.isExpandable(parent);
			
			ViewerFilter[] filters= fViewer.getFilters();
			Object[] children= ((ITreeContentProvider) fViewer.getContentProvider()).getChildren(parent);
			for (int i = 0; i < children.length; i++) {
				Object object= children[i];
				
				if (isEssential(object))
					return true;
				
				object= filter(object, parent, filters);
				if (object != null)
					return true;
			}
			return false;
		}