[MCLEAN-95] Add a fast clean option

[gnodet]

Jira issue: https://issues.apache.org/jira/browse/MCLEAN-95

This PR provides a fast clean option which can moves the target directory out of the way and actually deletes files in the background. Idea from apache/maven-mvnd#536 ...

For simple configurations (no filesets defined and no follow links), the directory to be deleted will be moved atomically to a different location (${maven.multiModuleProjectDirectory}/target/.clean by default) and a background thread is started to actually perform the deletion. If the atomic move can not be done, the usual deletion process will take place. When the maven session ends, a wait will happen to make sure all files are actually deleted. In case the deletion has not completed, when the deletion thread is started, it will first remove all pending files.

[slawekjaranowski]

look like new feature ... jira issue will be appreciated

[gnodet]

look like new feature ... jira issue will be appreciated

Yes, I will, I was first checking if there would be some reluctance or not.

[michael-o]

Will recheck tomorrow

[gnodet]

Btw, I had to use reflection to access the EventSpyDispatcher because the package is not exported. I don't think this is correct, especially as the object is available from the MavenExecutionRequest interface.

[rmannibucau]

@gnodet normally you can inject spies directly and do not need to unwrap them from the dispatcher, no?

[gnodet]

@gnodet normally you can inject spies directly and do not need to unwrap them from the dispatcher, no?

From a plugin ? My understanding is that EventSpy and AbstractMavenLifecycleParticipant only work for extensions, not for plugins.

[rmannibucau]

@gnodet the parent IoC is active while classes are visible I think so it should work, or did you mean EventSpy is not exported for plugins (thought it was). You can't call init/close methods since the lifecycle is managed by the dispatcher but calling a "fire" method should be fine. I don't recall without checking if you can inject directly List<SessionListener> with guice but it sounds like the solution if it works.

[gnodet]

@gnodet the parent IoC is active while classes are visible I think so it should work, or did you mean EventSpy is not exported for plugins (thought it was). You can't call init/close methods since the lifecycle is managed by the dispatcher but calling a "fire" method should be fine. I don't recall without checking if you can inject directly List<SessionListener> with guice but it sounds like the solution if it works.

EventSpy is exported, but plugins can not define such beans as they lookup is done in the container's realm which contains extensions, but not plugins afaik. I can double check that with a real test.

The problem here is that I needed a way for the plugin to be notified when the session ends and this is an unusual case because plugins are not really supposed to outlive their execution. Anyway, the way I found is to use mavenSession.getRequest().getEventSpyDispatcher().add(spy) but the EventSpyDispatcher class in in the org.apache.maven.eventspy.internal package which is not exported. This is bad because the method getEventSpyDispatcher() is itself part of the public api. Makes more sense ?

[rmannibucau]

@gnodet it was more to inject the spies to not use reflection, oh I see what you mean now, I read it the other way, sory about that

[gnodet]

@gnodet the parent IoC is active while classes are visible I think so it should work, or did you mean EventSpy is not exported for plugins (thought it was). You can't call init/close methods since the lifecycle is managed by the dispatcher but calling a "fire" method should be fine. I don't recall without checking if you can inject directly List<SessionListener> with guice but it sounds like the solution if it works.

EventSpy is exported, but plugins can not define such beans as they lookup is done in the container's realm which contains extensions, but not plugins afaik. I can double check that with a real test.

The problem here is that I needed a way for the plugin to be notified when the session ends and this is an unusual case because plugins are not really supposed to outlive their execution. Anyway, the way I found is to use mavenSession.getRequest().getEventSpyDispatcher().add(spy) but the EventSpyDispatcher class in in the org.apache.maven.eventspy.internal package which is not exported. This is bad because the method getEventSpyDispatcher() is itself part of the public api. Makes more sense ?

Actually, this is quite problematic as the getEventSpies() method has been removed from 4.x branch. We definitely need a clean API for that. I've fixed the code to use reflection on the field instead and raised https://issues.apache.org/jira/browse/MNG-7367 to provide a cleaner API.

[michael-o]

A few more nits