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
if (elementChildren == null) {
        	if (isTreePathContentProvider() && widget instanceof Item) {
				TreePath path = getTreePathFromItem((Item)widget);
				elementChildren = getSortedChildren(path);
			} else {
				elementChildren = getSortedChildren(parent);
			}
        }
        Control tree = getControl();
        
        int oldCnt = -1;
        if (widget == tree) {
			oldCnt = getItemCount(tree);
		}
        Item[] items = getChildren(widget);
        
        CustomHashtable expanded = newHashtable(CustomHashtable.DEFAULT_CAPACITY); 
        for (int i = 0; i < items.length; ++i) {
            if (getExpanded(items[i])) {
                Object element = items[i].getData();
                if (element != null) {
                    expanded.put(element, element);
                }
            }
        }
        int min = Math.min(elementChildren.length, items.length);