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
}
        return null;
    }
    /**
     * Copies the attributes of the given element into the given SWT item.
     * 
     * @param item
     *           the SWT item
     * @param element
     *           the element
     */
    protected abstract void doUpdateItem(Item item, Object element);
    
    protected void doUpdateItem(Widget widget, Object element, boolean fullMap) {
        if (widget instanceof Item) {
            Item item = (Item) widget;
            
            if (fullMap) {
                associate(element, item);
            } else {
            	Object data = item.getData();
            	if (data != null) {
            		unmapElement(data, item);
            	}
                item.setData(element);
                mapElement(element, item);
            }
            
            SafeRunnable.run(new UpdateItemSafeRunnable(item, element));
        }