Program: 178443
Project: 178443
Buggy source:
@Override public void onKeyDown(KeyDownEvent event){
  final int keyCode=event.getNativeKeyCode();
  Selection selection=getTextArea().getDocument().getSelection();
  if (selection.getRangeCount() > 0) {
    Range range=selection.getRangeAt(0);
    logRange(range);
    if (keyCode == KeyCodes.KEY_BACKSPACE || keyCode == KeyCodes.KEY_DELETE || keyCode == KeyCodes.KEY_ENTER) {
      range=EditorUtils.normalizeCaretPosition(range);
      log.fine("String_Node_Str");
      logRange(range);
    }
    Node startContainer=range.getStartContainer();
    Node endContainer=range.getEndContainer();
    TreeOperation op=null;
switch (keyCode) {
case KeyCodes.KEY_BACKSPACE:
{
        if (Node.TEXT_NODE == startContainer.getNodeType()) {
          op=handleBackspaceOnTextNode(range);
        }
 else         if (Node.ELEMENT_NODE == startContainer.getNodeType()) {
          op=handleBackspaceOnElement(range);
        }
        if (op == null) {
          event.preventDefault();
        }
      }
    break;
case KeyCodes.KEY_DELETE:
{
    if (Node.TEXT_NODE == startContainer.getNodeType()) {
      op=handleDeleteOnTextNode(range);
    }
 else     if (Node.ELEMENT_NODE == startContainer.getNodeType()) {
      op=handleDeleteOnElement(range);
    }
    if (op == null) {
      event.preventDefault();
    }
  }
break;
case KeyCodes.KEY_ENTER:
{
if (Node.TEXT_NODE == endContainer.getNodeType()) {
  op=handleEnterOnTextNode(range);
}
 else if (Node.ELEMENT_NODE == endContainer.getNodeType()) {
  op=handleEnterOnElement(range);
}
if (op == null) {
  event.preventDefault();
}
}
break;
default :
break;
}
if (op != null) {
if (!(op instanceof TreeInsertText || op instanceof TreeDeleteText)) {
event.preventDefault();
}
clientJupiter.generate(op);
}
}
}

Fixed version (ground truth):
@Override public void onKeyDown(KeyDownEvent event){
  final int keyCode=event.getNativeKeyCode();
  Selection selection=getTextArea().getDocument().getSelection();
  if (selection.getRangeCount() > 0) {
    Range range=selection.getRangeAt(0);
    logRange(range);
    if (keyCode == KeyCodes.KEY_BACKSPACE || keyCode == KeyCodes.KEY_DELETE || keyCode == KeyCodes.KEY_ENTER) {
      range=EditorUtils.normalizeCaretPosition(range);
      log.fine("String_Node_Str");
      logRange(range);
    }
    Node startContainer=range.getStartContainer();
    Node endContainer=range.getEndContainer();
    TreeOperation op=null;
switch (keyCode) {
case KeyCodes.KEY_BACKSPACE:
{
        if (Node.TEXT_NODE == startContainer.getNodeType()) {
          op=handleBackspaceOnTextNode(range);
        }
 else         if (Node.ELEMENT_NODE == startContainer.getNodeType()) {
          op=handleBackspaceOnElement(range);
        }
        if (op == null) {
          event.preventDefault();
        }
      }
    break;
case KeyCodes.KEY_DELETE:
{
    if (Node.TEXT_NODE == startContainer.getNodeType()) {
      op=handleDeleteOnTextNode(range);
    }
 else     if (Node.ELEMENT_NODE == startContainer.getNodeType()) {
      op=handleDeleteOnElement(range);
    }
    if (op == null) {
      event.preventDefault();
    }
  }
break;
case KeyCodes.KEY_ENTER:
{
if (Node.TEXT_NODE == endContainer.getNodeType()) {
  op=handleEnterOnTextNode(range);
}
 else if (Node.ELEMENT_NODE == endContainer.getNodeType()) {
  op=handleEnterOnElement(range);
}
if (op == null) {
  event.preventDefault();
}
}
break;
default :
break;
}
if (op != null) {
if (!(op instanceof TreeInsertText)) {
event.preventDefault();
}
clientJupiter.generate(op);
}
}
}