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
}
    /**
     * Sets the expanded state of all items to correspond to the given set of
     * expanded tree paths.
     * 
     * @param expandedTreePaths
     *           the set (element type: <code>TreePath</code>) of elements
     *           which are expanded
     * @param widget
     *           the widget
     */
    private void internalSetExpandedTreePaths(CustomHashtable expandedTreePaths, Widget widget, TreePath currentPath) {
        Item[] items = getChildren(widget);
        for (int i = 0; i < items.length; i++) {
            Item item = items[i];
            Object data = item.getData();
            TreePath childPath = data==null ? null: currentPath.createChildPath(data);
            if (data != null && childPath!=null) {
                
                
                boolean expanded = expandedTreePaths.remove(childPath) != null;
                if (expanded != getExpanded(item)) {
                    if (expanded) {
                        createChildren(item);
                    }
                    setExpanded(item, expanded);
                }
            }
            internalSetExpandedTreePaths(expandedTreePaths, item, childPath);
        }