Fwd: [maven-compiler-plugin] Issue with compiling test source using modules using a multi-version maven project.

[Claudio Corsi]

 Oops sent this to the wrong email.... Sent from my iPhone Begin forwarded message: From: Claudio Corsi <clco...@yahoo.com> Date: December 15, 2020 at 20:38:30 EST To: dev-h...@maven.apache.org Subject: [maven-compiler-plugin]  Issue with compiling test source using modules using a multi-version maven project.  Hi All, I am using maven to develop a java agent that uses a multi-version jar file.  This is being developed within a single project module instead of using multiple modules.  The issue is that my initial jar file will default compilation target is jdk 7 and it includes classes for jdk 9.  The issue is that I am creating a test that is using modules and when I try to build the module specific test code.  I get the UnsupportedOperationException that includes the message:     Can't compile test sources when main sources are missing a module descriptor This is generated within the TestCompilerMojo#preparePaths method.  I tried to get around this issue by adding compiler specific attributes in the pom file but alas I was not able to get around this issue.  I then forked the maven-compiler-plugin code and updated the code.  I was able to get around this issue by adding the following code to the mentioned method.         // It is possible that we are building a multi-version jar file in which the main classes are not module based.         if ( ! mainModuleDescriptorClassFile.exists() && release != null )         {             // @todo does it really matter that we check the version?             int version = Integer.valueOf( release );             if ( version >= 9 )             {                 String releaseOutputDirectory = String.format( "%s%sMETA-INF%sversions%s%d",                         getProject().getBuild().getOutputDirectory(), File.separator, File.separator,                         File.separator, version );                 // @todo how to add the releaseOutputDirectory automatically?                 // testPath.add( releaseOutputDirectory );                 mainModuleDescriptorClassFile =  new File ( releaseOutputDirectory, "module-info.class" );                 if ( getLog().isDebugEnabled() )                 {                     getLog().debug( "Updated main module " + mainModuleDescriptorClassFile );                 }             }         } This was add after the initial for loop for the master branch (3.9.0-SNAPSHOT).  I was able to get around the initial exception but alas I was still having issues building the test source.  I then was able to get around the issue by adding the following compilerArgs to my pom file:               <compilerArgs>                 <compilerArg>--module-path</compilerArg>                 <compilerArg>${project.basedir}/target/classes/META-INF/versions/9</compilerArg>               </compilerArgs> This allowed me to build the test source for that specific test module. I then was wondering if there is a better solution to this issue and I noticed that if I added the releaseOutputDirectory to the testPath collection then the above compilerArgs would not be required to be able to build the test sources.  My question then is, "Is their a better way then adding the directory to the testPath?".   I worry that the above solution will not work in all cases and can be a maintenance nightmare.  It seems that being forced to include the compileArgs to the test source build is a better overall solution.  Any opinions or comments on the above proposal? I've attach the test pom and patched TestCompilerMojo files. Thanks, --Claudio

TestCompilerMojo.java
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pom.xml
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