Clean fails to clean orphaned build files

[elharo]

Affected version

3.5.0 et al

Bug description

Clean currently misses generated files that are .gitignored and relics of previous builds after the pom.xml that built them is deleted.

See

apache/maven-resolver#1943
apache/maven#11800

related but not the same: https://issues.apache.org/jira/browse/RAT-476 (Fixing this bug would keep the RAT plugin from failing a build based on the gitignored files, but would not remove them. They would remain uncleaned in the project directory.)

"The Clean Plugin is used when you want to remove files generated at build-time in a project's directory."

Are there files generated at build-time in a project's directory? Yes.
Is the clean plugin failing to remove them? Yes.

[cstamas]

This is totally out of the scope for this plugin. From site: https://maven.apache.org/plugins/maven-clean-plugin/

The Clean Plugin is used when you want to remove files generated at build-time in a project's directory.

Your ask is to go beyond project's directory. I would argue this is developer (yours) or possibly SCM tool (ie git) job to do. What you effectively want, is m-clean-p to perform git clean for you, which is IMHO a nonsense.

Did you leave them there BEFORE doing the checkout update? Yes
Did you perform mvn clean BEFORE updating the checkout? NO
Is the clean plugin failing to remove them? Usually when a module is refactored (removed, renamed or removed), hence, that directory goes "out of the scope" for project. And, by definition above, clean nor maven itself will not try to figure out what should it do with it (should it look into SCM history and figure out "this was a module, but removed/moved"? Or should go berserk and no not-a-Maven directory should exist within project, should Maven just remove /docs and everything blindly?)

[elharo]

It's not beyond the projects' directory. It is inside the project's directory. The project directory is what was checked out form the source code repo. The uncleaned files are build artifacts created in the directory by maven. This is exactly what the clean plugin is supposed to clean.

The rest is implementation details. You are explaining why the current plugin has failed to clean them. This is not a reason not to clean them.

The clean plugin should not remove things that are not build artifacts, but it should remove things that are build artifacts. These are build artifacts. Ergo they should be removed.

I can think at least three different ways these files could be correctly removed, only one of which involves looking at the revision history. There are probably others. But the current approach of considering only artifacts produced by current POMs misses some build artifacts. It is insufficient. We need better.

[cstamas]

"These are build artifacts." -- untrue. Instead "They were build artifacts" until you performed update, and from that moment (as git modified files on disk, not Maven) "These are not build artifacts" stands as project "is gone" around them.