only scan relevant classpaths for metadata

[Bananeweizen]

• don't scan the com.* package hierarchy
• calculate the common root packages of all known packages with checks and metadata instead
• scans only the ...puppycrawl... and net.fs...samplechecks packages in a default developer runtime now

This still finds all relevant metadata files, but takes 480 ms instead of 12 seconds on my laptop.

fixes #515

[rnveach]

You confirm it still finds and loads sevntu's YML?
https://github.com/sevntu-checkstyle/sevntu.checkstyle/blob/master/eclipsecs-sevntu-plugin/src/com/github/sevntu/eclipse-metadata.yml

[rnveach]

Unrelated but Reflections should be removed. It doesn't work as expected on newer JREs and the repo is abandoned. I brought this up before and to main repo as well.
#659 (comment)

[Bananeweizen]

@rnveach It finds that package when the sevntu plugin is running:

However, neither on master nor on my branch any metadata file is found by scanning the classpath.

Regarding the reflections library: If you know a good alternative, then please raise an issue for replacing reflections.org. Don't be confused, I will probably add it to the target platform in another PR soon, where I'm working on consuming the checkstyle.jar instead of the checkstyle-all.jar. Adding it is only to move the dependency to this project instead of taking it transitively from checkstyle.

[rnveach]

However, neither on master nor on my branch any metadata file is found by scanning the classpath.

I assume this is related to other issues/comments on the matter as sevntu has been broken for a while. I am just confused if you say it won't load the YML or if it won't load something else?

If you know a good alternative

I believe Reflections right now is just doing the very basic load (common java code), so I would recommend doing that. No extra library needed. I do not remember the specifics as it has been a while since I originally looked into it.

[Bananeweizen]

I am just confused if you say it won't load the YML or if it won't load something else?

It doesn't find any YML. So there is no loading.

[rnveach]

Thanks. So this probably related to the reflections library. Since it doesn't work properly in Java 9+, it isn't finding anything.

[Bananeweizen]

@rnveach I've changed the implementation, and now the classgraph library is used instead. It finds the sevntu checks, but unfortunately it still uses 7 seconds of CPU time. Nevertheless I consider this change fixing both the performance gap as well as the reflections issue.

[Bananeweizen]

I'm going to merge this and the 2 PRs that are based on it. Feel free to still review and comment, so I can address comments separately, if necessary. However, I have some more classpath related changes (like trying to use the slim checkstyle.jar and to remove the guava dependencies) coming up, and all these changes are in conflict with each other because they change how the different plugin projects depend on each other.