That this update replaces maven-shared, maven-plugins-pom and maven-skins (already retired in Fedora) therefore appropriate Obsoletes/Provides should be added. After merging this PR maven-shared and maven-plugins-pom can be retired.

maven-shared is not maintained by the stewardship SIG - or not at all, I can't tell.
the package hasn't been touched by anyone but @mizdebsk or mass rebuilds for three years.

I'll happily retire it as a provenpackager.

Obsoletes/Provides for maven-skins were not added.

maven-skins has been retired since fedora 23. I don't see any reason to add references to it for fedora 31.

23? Well in that case I agree with you.

I have no idea how needed or dangerous this update is. I cannot provide more feedback.

I did some test rebuilds of dependent packages, and found a lot of strange errors like these:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:3.0.1:aggregate (default-cli) on project maven: An error has occurred in Javadoc report generation: Unable to resolve artifact:groupId = 'org.codehaus.plexus'
[ERROR] artifactId = 'plexus-javadoc'

Almost all maven plugins fail to build unless I add %pom_remove_plugin :maven-javadoc-plugin in this package (maven-parent). @mizdebsk do you know anything about this?

I did the test builds in this COPR repo:
https://copr.fedorainfracloud.org/coprs/decathorpe/maven-parent-pr/monitor/

No,I haven't seen this issue. In modules we are not using maven-javadoc-plugin - XMvn is used instead.

XMvn javadoc makes javadocs more consistent between packages - it unifies javadoc options, doclet used, CSS styles, and so on. It opens possibilities for better integration with distributions in the future, like for example distro-specific themes, links or dependencies between javadoc packages. It also has much fewer dependencies, which means smaller builroots and faster builds.

So ... what do you think we should do about this here?

I'd rather have modular and non-modular packages not diverge too far, otherwise it will get more and more difficult to merge necessary changes back and forth.

You need to add Requires: mvn(org.apache.maven.plugin-tools:maven-plugin-tools-javadoc) to maven-parent. This requires was not generated automatically and needs to be declared explicitly in the spec file.

Adding this fixed some builds, but the majority still fails with the same error - for example, for maven2:

[WARNING] The POM for org.codehaus.plexus:plexus-javadoc:jar:1.0 is missing, no dependency information available
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] 
[INFO] Maven 2.2.1 ........................................ FAILURE [  3.585 s]
[INFO] Maven Artifact ..................................... SUCCESS [  2.674 s]
[INFO] Maven Artifact Manager ............................. SUCCESS [  1.135 s]
[INFO] Maven Model ........................................ SUCCESS [  2.108 s]
[INFO] Maven Monitor ...................................... SUCCESS [  0.225 s]
[INFO] Maven Plugin Descriptor Model ...................... SUCCESS [  0.573 s]
[INFO] Maven Plugin Registry Model ........................ SUCCESS [  0.305 s]
[INFO] Maven Profile Model ................................ SUCCESS [  0.385 s]
[INFO] Maven Local Settings Model ......................... SUCCESS [  0.314 s]
[INFO] Maven Project Builder .............................. SUCCESS [  1.070 s]
[INFO] Maven Toolchains 2.2.1 ............................. SUCCESS [  0.670 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 15.579 s
[INFO] Finished at: 2019-05-31T10:42:45Z
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:3.0.1:aggregate (default-cli) on project maven: An error has occurred in Javadoc report generation: Unable to resolve artifact:groupId = 'org.codehaus.plexus'
[ERROR] artifactId = 'plexus-javadoc'
[ERROR] version = '1.0': Cannot access central (https://repo.maven.apache.org/maven2) in offline mode and the artifact org.codehaus.plexus:plexus-javadoc:jar:1.0 has not been downloaded from it before.

I tried querying the rawhide repos but it looks like the thing that's missing (org.codehaus.plexus:plexus-javadoc) isn't available from any existing package.

Upstream removed dependency plexus-javadoc in commit 6b8b444. You can backport that patch. More details are in JIRA: https://issues.apache.org/jira/browse/MPOM-217

Yep, that did the trick. Thanks!

I did another round of rebuilds of affected packages, and this is the - much better - result:
https://copr.fedorainfracloud.org/coprs/decathorpe/maven-parent-pr-test/monitor/

As far as I can tell, nothing breaks that wasn't already broken - except one package (maven-stage-plugin), which fails due to usage of some "banned dependency" :laughing:

Build failure due to "banned dependencies" can be fixed by removing invocation of Maven Enforcer Plugin (%pom_remove_plugin -r :maven-enforcer-plugin in %prep)

Thanks, that worked. Now all packages that build successfully without this update also build successfully with this update.