Maven - why does running a build of multiple packages result in a different result?

Question

Let's say I have a project with 2 modules, and 3 pom.xml files (1 for Module A, 1 for Module B, 1 parent pom.xml)

I've added the following plugin that verifies the code coverage diff between my changeset and another branch, and fails if it's below a certain threshold https://github.com/SurpSG/diff-coverage-maven-plugin

If I make NO code changes:

mvn clean verify -> success

mvn clean verify -T 1C -pl moduleA -am -U -> success

mvn clean verify -T 1C -pl moduleA, moduleB -am -U -> success

So as expected, my builds are passing because I made no code change.

Now if I make a code change to moduleA without proper unit test code coverage, here are the results.

mvn clean verify -T 1C -pl moduleA -am -U -> fail for moduleB, skipping moduleA

mvn clean verify -T 1C -pl moduleB -am -U -> success

mvn clean verify -T 1C -pl moduleA, moduleB -am -U -> fail for moduleB, skipping moduleA

This last case is what is puzzling me, why would moduleB be failing? why is it not running for each module without side-effects?

The issue is that the failure message is really not helpful and pointing to the wrong service.

Can you create a Small public repository demonstrating this behavior? — Thorbjørn Ravn Andersen, Aug 28 '22 at 19:57

score 2 · Accepted Answer · answered Aug 29 '22 at 04:40

You are observing some weird behaviour because plugin's author didn't pay much attention to maven internals:

private val rootProjectDir: File
  get() = reactorProjects[0].basedir

private fun collectExecFiles(): Set<File> {
 return if (dataFileIncludes == null) {
   setOf(dataFile)
 } else {
   FileUtils.getFiles(rootProjectDir, dataFileIncludes, dataFileExcludes).toSet()
 }
}

Injecting reactorProjects makes sense for @aggregator mojos, because when we are dealing with multi-module project structures and have parent-child relations we need special handling of such cases (for example, there are two mojos in jacoco-maven-plugin: report and report-aggregate). In your case plugin's author is trying to kill two rabbits with single shot, that in your particular case leads to the following:

when you run maven like -pl moduleA -am then when maven executes verify phase of Module B reactor projects are Module A, Module B, plugin tries to pick up exec files from Module A directory and fails: Module A depends on Module B and there are no exec files in Module A directory.

Maven - why does running a build of multiple packages result in a different result?

1 Answers1