François Guillot created MNG-8066:
-------------------------------------
Summary: Maven hangs on self-referencing exceptions
Key: MNG-8066
URL: https://issues.apache.org/jira/browse/MNG-8066
Project: Maven
Issue Type: Bug
Reporter: François Guillot
If the code executed by Maven throws a self-referencing exception, such as
{code:java}
RuntimeException selfReferencingException = new RuntimeException("BOOM self");
selfReferencingException.initCause(new Exception("BOOM cause",
selfReferencingException));
throw selfReferencingException;
{code}
For instance, if this code is added to an `AbstractExecutionListener`, which is
added to the running build:
{code:java}
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;
}
}
{code}
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
{code:java}
Set<Throwable> dejaVu = Collections.newSetFromMap(new IdentityHashMap<>());
{code}
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
{code:java}
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;
}
}
{code}
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