Description thammers 2011-05-12 01:40:23 EDT

Build Identifier: I20110428-0848

Its hard for a CommandStackListener to distinguish whether its commandStackChanged() method was called from the (Basic)CommandStack because of an actual command execution (execute, redo, undo) or because of flushing the CommandStack. A simple workaround is to cache the last mostRecentCommand in the CommandStackListener and do a simple reference check against the the "new" mostRecentCommand. But this does not consider the fact, that commands are stateful (executed, undone, redone). If the mostRecentCommand in the BasicCommandStack would be set to null before notifying the command stack listeners these listeners would be able to realize that the command stack has been flushed (or according to the current implementation a RuntimeException occured during execute/undo/redo).

Reproducible: Always

Steps to Reproduce:
import java.util.EventObject;

import org.eclipse.emf.common.command.BasicCommandStack;
import org.eclipse.emf.common.command.Command;
import org.eclipse.emf.common.command.CommandStack;
import org.eclipse.emf.common.command.CommandStackListener;
import org.eclipse.emf.common.command.IdentityCommand;

public class FlushTest {
  
  public static void main(final String[] args) {
    final BasicCommandStack cmdStack = new BasicCommandStack();
    cmdStack.addCommandStackListener(new CommandStackListener() {
      Command lastCmd;
      @Override
      public void commandStackChanged(final EventObject event) {
        final Command cmd = ((CommandStack) event.getSource()).getMostRecentCommand();
        if (cmd == lastCmd) {
          throw new IllegalStateException("mostRecentCommand has not changed");
        }
        lastCmd = cmd;
      }
    });
    cmdStack.execute(new IdentityCommand());
    cmdStack.flush(); // boom
  }
  
}