maven-configuration-reproducer

Related to MNG-7709

During Maven 3.9.0 upgrade we noticed a change in behavior in how configuration is parsed. It seems to manifest when you try to clear plugin configuration, while also reconfiguring that same plugin inside a profile (in the same pom). The setup in this repo is:

• parent module configures the shade plugin with an outputFile parameter
• child module clears this configuration (using <configuration combine.self="override"/>)
• child module also has a profile which configures the shade plugin (adding a finalName parameter)
• nested-child module activates this profile

It is expected that child and nested-child do not inherit the outputFile parameter, because the shade configuration is removed in child pom.xml. This works in Maven 3.8.7, but in Maven 3.9.0 the nested-child module does inherit the outputFile parameter. I assume this has something to do with the profile getting activated and causing the configuration to not get merged properly, but I'm not sure.

I also built a custom version of Maven 3.9.0 which uses plexus-utils 3.3.1, and the behavior is back to normal. So I think the behavior change is in plexus-utils (although it could be that Maven is "mis-using" plexus-utils, and the plexus-utils change is technically correct). I tested with a few different plexus-utils versions and it seems like the behavior change was introduced in plexus-utils 3.4.0 (I also tested with plexus-utils 3.5.0 and this issue is not fixed).

Observed behavior with Maven 3.8.7 (which uses plexus-utils 3.3.1)

Checking parent module configuration with:
apache-maven-3.8.7/bin/mvn help:effective-pom -N | grep outputFile | wc -l
✅ Prints 1, meaning the configuration contains an outputFile parameter, which is expected

Checking child module configuration with:
apache-maven-3.8.7/bin/mvn help:effective-pom -pl child | grep outputFile | wc -l
✅ Prints 0, meaning the configuration does not contain an outputFile parameter, which is expected

Checking nested-child module configuration with:
apache-maven-3.8.7/bin/mvn help:effective-pom -pl child/nested-child | grep outputFile | wc -l
✅ Prints 0, meaning the configuration does not contain an outputFile parameter, which is expected

Checking all modules with:
apache-maven-3.8.7/bin/mvn help:effective-pom | grep outputFile | wc -l
✅ Prints 1, meaning only parent module contains an outputFile parameter, which is expected

Observed behavior with Maven 3.9.0 (which uses plexus-utils 3.4.2)

Checking parent module configuration with:
apache-maven-3.9.0/bin/mvn help:effective-pom -N | grep outputFile | wc -l
✅ Prints 1, meaning the configuration contains an outputFile parameter, which is expected

Checking child module configuration with:
apache-maven-3.9.0/bin/mvn help:effective-pom -pl child | grep outputFile | wc -l
✅ Prints 0, meaning the configuration does not contain an outputFile parameter, which is expected

Checking nested-child module configuration with:
apache-maven-3.9.0/bin/mvn help:effective-pom -pl child/nested-child | grep outputFile | wc -l
❌ Prints 1, meaning the configuration contains an outputFile parameter, which is NOT expected

Checking all modules with:
apache-maven-3.9.0/bin/mvn help:effective-pom | grep outputFile | wc -l
❌ Prints 2, meaning parent and nested-child modules both contain an outputFile parameter, which is NOT expected

Observed behavior with Maven 3.9.0 (built against plexus-utils 3.3.1)

Checking parent module configuration with:
apache-maven-3.9.0-plexus-3.3.1/bin/mvn help:effective-pom -N | grep outputFile | wc -l
✅ Prints 1, meaning the configuration contains an outputFile parameter, which is expected

Checking child module configuration with:
apache-maven-3.9.0-plexus-3.3.1/bin/mvn help:effective-pom -pl child | grep outputFile | wc -l
✅ Prints 0, meaning the configuration does not contain an outputFile parameter, which is expected

Checking nested-child module configuration with:
apache-maven-3.9.0-plexus-3.3.1/bin/mvn help:effective-pom -pl child/nested-child | grep outputFile | wc -l
✅ Prints 0, meaning the configuration does not contain an outputFile parameter, which is expected

Checking all modules with:
apache-maven-3.9.0-plexus-3.3.1/bin/mvn help:effective-pom | grep outputFile | wc -l
✅ Prints 1, meaning only parent module contains an outputFile parameter, which is expected