Bug 138608 [Viewers] JFace AbstractTreeViewer: itemExists doesn't handle equal tree entries
I use a TreeViewer with - setUseHashLookup(true) - without any sorter or filter - with a comparer When I try to add an object that is equal to an existing entry in the tree, it will not be added. This is because the method private boolean itemExists(Item[] items, Object element) { if(usingElementMap()) { return findItem(element) != null; } for (int i = 0; i < items.length; i++) { if(items[i].getData().equals(element)) { return true; } } return false; } takes a shortcut if there is an element map, but the shortcut doesn't handle the 'multiple equal elements' case. There is a workaround, however: Setting a dummy sorter will avoid the call to itemExists and multiple equal elements can be added to the tree.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
private Object element;
        private Item item;
        UpdateItemSafeRunnable(Item item, Object element) {
            this.item = item;
            this.element = element;
        }
        public void run() {
            doUpdateItem(item, element);
        }
        
    }
    /**
     * Creates an abstract tree viewer. The viewer has no input, no content
     * provider, a default label provider, no sorter, no filters, and has
     * auto-expand turned off.
     */
    protected AbstractTreeViewer() {
        
    }
    /**
     * Adds the given child elements to this viewer as children of the given
     * parent element. If this viewer does not have a sorter, the elements are
     * added at the end of the parent's list of children in the order given;
     * otherwise, the elements are inserted at the appropriate positions.