[NETBEANS-4754] Action gets called with wrong context until garbage collection

• Type: Bug
• Status: In Progress
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 12.0
• Component/s: platform - Actions

Environment

NetBeans Platform application running on NetBeans Platform 12.0 on Windows 10 / Java 13.0.2.

• Assignee: Svatopluk Dedic
• Reporter: Eirik Bakke
• Created: 30/Aug/20 05:19
• Updated: 01/Sep/20 07:52

Description

My NetBeans Platform application has an action declared as follows:

@ActionID(category = "Ultorg", id = "com.ultorg.actionids.FieldsAction")
@ActionRegistration(displayName = "#CTL_FieldsAction")
@Messages("CTL_FieldsAction=Fields & Joins...")
public class FieldsAction implements ActionListener {
  private final ToolboxInvoker invoker;

  public FieldsAction(ToolboxInvoker invoker) {
    Preconditions.checkNotNull(invoker);
    this.invoker = invoker;
  }

  @Override
  public void actionPerformed(ActionEvent e) {
    invoker.invoke();
  }
}

The ToolboxInvoker context is provided by the lookup of a custom TopComponent implementation. When I have multiple such TopComponent tabs open, switching between them, and invoking the action above with a keyboard shortcut, the wrong FieldsAction instance will occasionally be called (i.e. an instance with the wrong ToolboxInvoker context).

After some debugging, the problem seems to be caused by https://github.com/apache/netbeans/pull/652 , specifically by ContextAction.delegate0 assuming that instDelegate can be used as a cached value without checking whether the lookup (data parameter) has changed. Or perhaps instDelegate was supposed to be cleared elsewhere whenever the lookup changes--but this is not happening properly.

Because the instDelegate field holds only weak references, the buggy state only lasts until the next garbage collection.

Issue Links

• relates to: NETBEANS-1985 Stateful context action does not initialize properly