Bug 129193 [JFace] Setting the sorter on AbstractTreeViewer before input can cause NPE
I have a scenario with a subclass of TreePathViewerSorter is set on a subclass of AbstractTreeViewer. AbstractTreeViewer.setSorter() calls refresh, which eventually ends up here: // AbstractTreeViewer: /* (non-Javadoc) * @see org.eclipse.jface.viewers.StructuredViewer#getSortedChildren(java.lang.Object) */ protected Object[] getSortedChildren(Object parentElementOrTreePath) { Object[] result = getFilteredChildren(parentElementOrTreePath); ViewerSorter sorter = getSorter(); if (sorter instanceof TreePathViewerSorter) { TreePathViewerSorter tpvs = (TreePathViewerSorter) sorter; // be sure we're not modifying the original array from the model result = (Object[]) result.clone(); TreePath path = null; if (parentElementOrTreePath instanceof TreePath) { path = (TreePath) parentElementOrTreePath; } else { (1) Object parent = parentElementOrTreePath; (2) Widget w = internalGetWidgetToSelect(parent); if (w != null) { path = internalGetSorterParentPath(w, sorter); } if (path == null) path = TreePath.EMPTY.createChildPath(parentElementOrTreePath); } tpvs.sort(this, path, result); } else if (sorter != null) { // be sure we're not modifying the original array from the model result = (Object[]) result.clone(); sorter.sort(this, result); } return result; } At line (1) parent is null and at line (2) it eventually gets down into findItems(): // StructuredViewer: protected final Widget[] findItems(Object element) { Widget result = doFindInputItem(element); if (result != null) return new Widget[] { result }; // if we have an element map use it, otherwise search for the item. if (usingElementMap()) { (3) Object widgetOrWidgets = elementMap.get(element); if (widgetOrWidgets==null) { return NO_WIDGETS; } else if (widgetOrWidgets instanceof Widget) { return new Widget[] {(Widget) widgetOrWidgets}; } else { return (Widget[])widgetOrWidgets; } } result = doFindItem(element); return result == null ? NO_WIDGETS : new Widget[] { result }; } Here at (3), element is null, and the HashMap throws an NPE when trying to call key.hashCode() (since key is null).
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
protected void internalRefresh(Object element) {
        internalRefresh(element, true);
    }
    
    protected void internalRefresh(Object element, boolean updateLabels) {
        
        if (element == null) {
            internalRefresh(getControl(), getRoot(), true, updateLabels);
            return;
        }
        Widget[] items = findItems(element);
        if (items.length != 0) {
			for (int i = 0; i < items.length; i++) {
				
				internalRefresh(items[i], element, true, updateLabels);
			}            
        }
    }
    /**
     * Refreshes the tree starting at the given widget.
     * <p>
     * EXPERIMENTAL.  Not to be used except by JDT.
     * This method was added to support JDT's explorations
     * into grouping by working sets, which requires viewers to support multiple 
     * equal elements.  See bug 76482 for more details.  This support will
     * likely be removed in Eclipse 3.2 in favour of proper support for
     * multiple equal elements. 
     * </p>
     *