This extension provides a org.apache.maven.eventspy.EventSpy custom implementation.
You can listen to events triggered by Maven execution.

If you're trying to observe specific things done by a mojo, it seems unlikely that the mojo will triggered an event.

You can try do track all the execution of fr.jcgay.maven.profiler.ProfilerEventSpy#onEvent within your build to see if an interesting event comes up but it seems to be a long shot 😇

It should be possible to implements custom events but it implies that a mojo uses org.apache.maven.eventspy.internal.EventSpyDispatcher which lives in an internal package 😅.

If you're trying to observe specific things done by a mojo, it seems unlikely that the mojo will triggered an event.

Just say I have full control over the mojo code could the mojo emit events that are understood by maven-profiler?

org.apache.maven.eventspy.internal.EventSpyDispatcher which lives in an internal package

Thanks for the hint, even though its internal I won't mind using that, do you think maven-profiler could define some kind of custom event that could be used for such purpose?

Another way I could think of would be that maven-profiler provides a (public) component where one could send events directly?

For example ProfilerEventSpy could have a method recordStart(String name) and recordStop(String name) methods or similar where name is used as an identifier?

I think you're right you may also be able to inject ProfilerEventSpy directly in your mojo (I have not tested it) and call onEvent with a custom event to be implemented in maven-profiler.
How will you report them ? I think they should be linked to the mojo goal running them ?

I think it must not be linked directly to a mojo more something like:

Action A: 30 sec
Action B: 2 sec

and so on...

I think you're right you may also be able to inject ProfilerEventSpy directly in your mojo (I have not tested it) and call onEvent with a custom event to be implemented in maven-profiler.

I played around a bit with this option and think one might even reuse some events here (e.g. repository download events), sadly this does not work out-of-the-box and I have opened apache/maven#740 to address this.