[jira] [Created] (NETBEANS-3196) Calling Children.LEAF.getNodesCount() changes lazy loading behavior globally

["Eirik Bakke (Jira)" <ji...@apache.org>]

Eirik Bakke created NETBEANS-3196:
-------------------------------------

             Summary: Calling Children.LEAF.getNodesCount() changes lazy loading behavior globally
                 Key: NETBEANS-3196
                 URL: https://issues.apache.org/jira/browse/NETBEANS-3196
             Project: NetBeans
          Issue Type: Improvement
          Components: platform - Nodes
    Affects Versions: 11.0
            Reporter: Eirik Bakke


There's a small bug in org.openide.nodes.Node.setChildren(Children). The logic goes something like this:

{code:java}
protected final void setChildren(final Children ch) {
  boolean wasInited = hierarchy.isInitialized();
  boolean wasLeaf = hierarchy == Children.LEAF;
  // ...
  hierarchy = ch;
  // ...
  if (wasInited && hierarchy != Children.LEAF) {
      // init new children if old was inited
      hierarchy.getNodesCount();
{code}

If a Node's children was originally Children.LEAF, and is then changed to a different instance, the resulting behavior now becomes dependent on the result of Children.LEAF.isInitialized(). The latter is a global piece of state which may return false for a long time until _any_ module anywhere in the IDE or in a platform application calls Children.LEAF.getNodesCount(), after which Children.LEAF.isInitialized() will forever after return true.

Once Children.LEAF.getNodesCount() has been called, from any module, Node implementations that switch from Children.LEAF to another Children implementation will no longer get lazy loading behavior.

The fix is simple; the condition should be "wasInited && !wasLeaf && hierarchy != Children.LEAF)". I will create a patch for this at some point, once I have made sure it doesn't cause any problems.

(This bug was found in a NetBeans Platform application that relies heavily on lazy loading of nodes.)



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