[MNG-8066] Maven hangs on self-referencing exceptions

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.9.8, 4.0.0-beta-4, 4.0.0
• Component/s: Core
• Assignee: Tamas Cservenak
• Reporter: François Guillot
• Created: 04/Mar/24 12:54
• Updated: 11/Jul/24 10:53
• Resolved: 06/Jun/24 10:31

Description

If the code executed by Maven throws a self-referencing exception, such as

RuntimeException selfReferencingException = new RuntimeException("BOOM self");
selfReferencingException.initCause(new Exception("BOOM cause", selfReferencingException));
throw selfReferencingException;

For instance, if this code is added to an `AbstractExecutionListener`, which is added to the running build:

import org.apache.maven.execution.AbstractExecutionListener;
import org.apache.maven.execution.ExecutionListener;
import org.apache.maven.execution.ExecutionEvent;

public class FailingExecutionListener extends AbstractExecutionListener {

  private final ExecutionListener delegate;

  public FailingExecutionListener(ExecutionListener delegate) {
    this.delegate = delegate;
  }

  @Override
  public void sessionStarted(ExecutionEvent event) {
    if (delegate != null) {
      delegate.sessionStarted(event);
    }
    RuntimeException selfReferencingException = new RuntimeException("BOOM self");
    selfReferencingException.initCause(new Exception("BOOM cause", selfReferencingException));
    throw selfReferencingException;
  }

}

Maven hangs at the end of the build, in `DefaultExceptionHandler`.

The code in `DefaultExceptionHandler#getMessage` iterates on a given throwable and its causes. It checks if the cause is not the same throwable, but doesn't protect against a 'two-level' recursion like shown above.

Note that when printing a stacktrace, Java itself protects against this via the use of a

Set<Throwable> dejaVu = Collections.newSetFromMap(new IdentityHashMap<>());

and stops the recursion if encountering an already seen throwable.

A way to fix this would be to replace the offending cause with a replacement with no cause, such as in

    private static Throwable patchCircularCause(Throwable current, Throwable parent) {
        try {
            Field causeField = Throwable.class.getDeclaredField("cause");
            causeField.setAccessible(true);
            Throwable replacement = new Throwable("[CIRCULAR REFERENCE: " + current + "]");
            replacement.setStackTrace(current.getStackTrace());
            causeField.set(parent, replacement);
            return replacement;
        } catch (NoSuchFieldException | IllegalAccessException e) {
            // Couldn't replace the cause, let's return the actual exception.
            return current;
        }
    }

Issue Links

• links to: GitHub Pull Request #1558