-localCheckoutDir does not work with multi-module projects

[dwnusbaum]

(The plugin-compat-tester component cannot be used in Jira anymore, so I guess GitHub issues are preferred?)

The -localCheckoutDir option does not work with multi-module projects even when there is an implementation of AbstractMultiParentHook for the plugin in question. Specifically, MultiParentCompileHook.isSnapshotMultiParentPlugin returns false, so the default process-test-classes goal is used instead of MultiParentCompileHook changing the goal to install, which fails (JENKINS-62658 describes the issue with process-test-classes more generally).

The problem seems to be that AbstractMultiParentHook intentionally doesn't do anything when localCheckoutDir is used, which means that these properties never get specified, so the properties are null here and the multi-module-specific logic gets skipped.

See #383 (comment) for some additional discussion specific to workflow-cps.

[jglick]

More generally I would like for the multimodule support to be rewritten. Should collect all the repos that need testing, then run Maven from the root of each of those. Do not want to just mvn test or mvn install in one pass, despite jenkinsci/maven-hpi-plugin#336, because -Djenkins.version=… would compile against the wrong core, but could do two passes.

[olamy]

To help with this, I proposed a change here
But I close the PR because it looks this will not being accepted.

[jglick]

Some discussion of the jenkins.version issue: jenkinsci/bom#1479 (comment)

[jglick]

CC @jtnord

[jglick]

Regarding mvn install on snapshots, https://maven.apache.org/resolver/local-repository.html#use-cases (3.9.0+) merits investigation.

[jtnord]

included in 1313.v036de64e1863