Wrong reproducer

This is simply wrong reproducer, what it tries to do is wrong, here is why:

Let's examine the mvn -am -pl plugin-dependency,a-module more obvious case. Am stating the "obvious" (maven console output) in order it happens with explanations:

1. Maven topologically sorts the projects it is about to build, console states:

[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO] 
[INFO] Parent POM                                                         [pom]
[INFO] A plugin dependency                                                [jar]
[INFO] A module                                                           [jar]

Hence, we see the order is: mvn-plugin-dependency-reactor-issue (parent), plugin-dependency and a-module.

2. First parent is being built:

[INFO] 
[INFO] ------------< com.acme:mvn-plugin-dependency-reactor-issue >------------
[INFO] Building Parent POM 1.0-SNAPSHOT                                   [1/3]
[INFO] --------------------------------[ pom ]---------------------------------

3. Build would invoke checkstyle:check goal on parent:

[INFO] 
[INFO] --- maven-checkstyle-plugin:3.1.2:check (default-cli) @ mvn-plugin-dependency-reactor-issue ---

4. Errors out with message:

Execution default-cli of goal org.apache.maven.plugins:maven-checkstyle-plugin:3.1.2:check failed: Plugin org.apache.maven.plugins:maven-checkstyle-plugin:3.1.2 or one of its dependencies could not be resolved

As expected, as plugin-dependency (used as dependency for check-style plugin) is NOT YET BUILT. As we saw above, it was planned to be built AFTER parent. But to build parent, it needs plugin-dependency, but to build plugin-dependency, it needs parent to be built....

Start by running mvn -am -pl plugin-dependency,a-module and reviewing the reported reactor build order and checkstyle failure. No source file or test is named, and the issue does not define a concrete change or acceptance condition, so the intended outcome needs clarification before implementation.