[MNG-7260] [MNG-7266] Remove maven-compat module

[gnodet]

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[cstamas]

Wow, massive! 31k LOC gone 😄

[cstamas]

Well, for a moment I was questioning my own sanity, but figured ("how does this pass" was bonging in my head). Well, you removed the module maven-compat, but you left the dependencies on it, that are coming back into build either from CI local repo or from remote RAO snapshots repo? Unsure, but one thing is certain: I did try this "at home" (remove maven-compat from build) and maven build should fail 😄

So, this is not so simple, as there are things to be reimplemented AFAIR...

[gnodet]

@cstamas I've removed the remaining references. The build still passes and my local repo does not contain any trace of this module (so not downloaded). Let's see what the IT tests results are...

[cstamas]

Hm, I did try removing maven-compat several months ago locally (just to see), and it was not simple back then. I might miss some more recent commits since it seems...

[rfscholte]

https://issues.apache.org/jira/browse/MNG-5995 ?

[michael-o]

Almost all Core ITs fail for me. Compat cannot be simply deleted w/o replacing parts used by Core.

[cstamas]

Almost all Core ITs fail for me. Compat cannot be simply deleted w/o replacing parts used by Core.

One remark: maven-compat removes maven2 compatibility, hence, if any of IT uses "plugin from maven2" (think install/deploy 2.x), they will fail, no? So to say, ITs should be upgraded to use 3.x line of plugins globally (as otherwise IT is about "Maven2 support in Maven3", no?) And hence, to be able to do that, we must tackle install/deploy (and any other plugin not at 3.x version)... as install/deploy 3.x have issues with maven-plugin metadata AFAIR, so I bet 2.x of those are generally used.

[rfscholte]

@MartinKanters and @mthmulders made a start with the 3.x implementation for these plugins.
You could also say: Maven ITs shouldn't test the logic of plugins. For most we have a mock implementation that just says: plugin x goal y executed. Could we rewrite the ITs so they don't need these plugins?

[gnodet]

The first problem hit by the integration tests is that the only implementation of org.apache.maven.repository.RepositorySystem is currently in maven-compat. I've just pushed an additional commit to get rid of it.

[rfscholte]

I wonder if the deleted files should be removed or moved to a new maven-compat3 module. I wouldn't be suprised if maven-plugins out these depend on one of these classes.

[gnodet]

I wonder if the deleted files should be removed or moved to a new maven-compat3 module. I wouldn't be suprised if maven-plugins out these depend on one of these classes.

Right. I'll get back to that once I found out why the tests fail on linux/windows and not on osx...

[cstamas]

I wonder if the deleted files should be removed or moved to a new maven-compat3 module. I wouldn't be suprised if maven-plugins out these depend on one of these classes.

But isn't that an indicator of our "slackness" then? Maven3 is out for 8 years and we still have (in house) plugins depending on Maven2 stuff?

[gnodet]

But isn't that an indicator of our "slackness" then? Maven3 is out for 8 years and we still have (in house) plugins depending on Maven2 stuff?

Well, I think @rfscholte refers to my last commit which removes the RepositorySystem interface which had not been deprecated (no idea why). I can bring it back with no implementation (I had to move a few constants that were used in maven-core from that class to the MavenRepositorySystem), but I have no idea if this class is used outside of maven-core for now.

[cstamas]

Well, I think @rfscholte refers to my last commit which removes the RepositorySystem interface which had not been deprecated (no idea why). I can bring it back with no implementation (I had to move a few constants that were used in maven-core from that class to the MavenRepositorySystem), but I have no idea if this class is used outside of maven-core for now.

In my "attempt" (to drop maven-compat) I did keep RepositorySystem as it is part of maven-core, and provided implementation for it in package org.apache.maven.bridge next to MavenRepositorySystem and reworked the two to share a LOT of common code/component.... (will try to dig up my "attempt" -- am talking from my memory only, so take this with a pinch of salt)

[mthmulders]

@MartinKanters and @mthmulders made a start with the 3.x implementation for these plugins.

That's right. It has been lingering a bit but I was actually planning to start working on it this Wednesday. The goal is (as per this JIRA comment to move the existing "install / deploy" logic into Core, implementing it on top of Maven Resolver API. The M-I-P and M-D-P will leverage that, but they will still need a fallback (implemented with Eclipse Aether) so they are compatible with Maven 3.1 and above.

[gnodet]

I'm having a hard time trying to understand why maven-compat is deprecated if it contains the only implementation of the RepositorySystem interface which is not deprecated. Most of the methods in this interface have been replicated in MavenRepositorySystem, but even the latest surefire uses one of the method that has no equivalent...

[rfscholte]

IIRC @jvanzyl moved it, so maybe he remembers it. (this is also the reason why adding @deprecated is so so so important)

[cstamas]

IMHO, the RepositorySystem and MavenRepositorySystem are (meant) to be the same thing (but one is v2/3 other is v3+). When I attempted to drop maven-compat, these are high level changes I went with:

1. moved the implementation of RepositorySystem to maven-core next to MavenRepositorySystem (started reworking it w/o compat bits)
2. refactored MavenRepositorySystem into interface and added Impl of it (a lot of static methods 😢 AFAIR).
3. tried to have as much shared code between the two as possible, so basically I had not two but 6 or more "shared" components around these two (but as "private detail", w/o exposed ifaces and really just to share logic)
4. lost that work on some of my laptops I wrote off (or reinstalled).... but can lend a hand a bit later on this

[gnodet]

IMHO, the RepositorySystem and MavenRepositorySystem are (meant) to be the same thing (but one is v2/3 other is v3+). When I attempted to drop maven-compat, these are high level changes I went with:

1. moved the implementation of RepositorySystem to maven-core next to MavenRepositorySystem (started reworking it w/o compat bits)
2. refactored MavenRepositorySystem into interface and added Impl of it (a lot of static methods 😢 AFAIR).
3. tried to have as much shared code between the two as possible, so basically I had not two but 6 or more "shared" components around these two (but as "private detail", w/o exposed ifaces and really just to share logic)
4. lost that work on some of my laptops I wrote off (or reinstalled).... but can lend a hand a bit later on this

I went to a slightly different direction. However, I'm hitting a problem. Some integration tests fail with NoClassDefFoundError for RepositorySystemSession. The reason is that the plugin realm for org.apache.maven.plugins:maven-plugin-plugin:maven-plugin:3.6.0 contains maven-compat-3.0.jar. The classes from that jar are usually hidden by the version coming from the maven distribution, however, since I removed it, they seem to surface and cause the exception. However, I'm not sure why the RepositorySystemSession isn't available. Is it maybe not considered part of the API and hence hidden ? Maybe that was working because the bean was previously loaded from the maven-compat jar coming from the same realm...

[gnodet]

The ArtifactDeployer and ArtifactInstaller, ArtifactCollector, ArtifactResolver interfaces contains various methods used in https://github.com/apache/maven-integration-testing/blob/master/core-it-support/core-it-plugins/maven-it-plugin-artifact/src/main/java/org/apache/maven/plugin/coreit and thus cause some failures in the ITs. Should I bring it back somehow or should I fix the testing plugins ? or get rid of the tests that do use indirectly those old interfaces ?

[michael-o]

The ArtifactDeployer and ArtifactInstaller, ArtifactCollector, ArtifactResolver interfaces contains various methods used in https://github.com/apache/maven-integration-testing/blob/master/core-it-support/core-it-plugins/maven-it-plugin-artifact/src/main/java/org/apache/maven/plugin/coreit and thus cause some failures in the ITs. Should I bring it back somehow or should I fix the testing plugins ? or get rid of the tests that do use indirectly those old interfaces ?

It needs to be evaluated whether those ITs are for Maven 2, or 2. If 2 only, we need to discuss whether to remove them. If 3+ we likely need to migrate them.