Support Maven 4 Module Source Hierarchy and module-info-patch.args for modular whitebox testing

[ascheman]

Summary

When using Maven 4's Module Source Hierarchy (modular source declarations in the POM) and module-info-patch.maven for whitebox testing of Java modules, surefire requires manual workarounds (classesDirectory, testClassesDirectory, useModulePath, argLine) that should not be necessary.

Problem

Maven 4 with maven-compiler-plugin 4.0.0-beta-4 compiles modular sources to a nested layout:

• target/classes/<module-name>/ instead of target/classes/
• target/test-classes/<module-name>/ instead of target/test-classes/

Additionally, maven-compiler-plugin generates target/test-classes/META-INF/maven/module-info-patch.args from module-info-patch.maven, containing --add-exports and --add-opens directives for test execution.

Surefire 3.5.5 / 3.6.0-SNAPSHOT does not handle either:

1. Module detection — findModuleDescriptor() looks for module-info.class directly in target/classes/ but misses the nested target/classes/<module-name>/module-info.class
2. Test class scanning — DirectoryScanner scans target/test-classes/ and finds <module-name>/pkg/Test.class, interpreting the module name as a package prefix
3. module-info-patch.args — surefire auto-generates --add-opens and --add-reads but does not read the compiler-generated args file containing --add-exports directives from module-info-patch.maven

Current workaround (surefire 3.5.5)

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>3.5.5</version>
  <configuration>
    <classesDirectory>${project.build.outputDirectory}/modfib</classesDirectory>
    <testClassesDirectory>${project.build.testOutputDirectory}/modfib</testClassesDirectory>
    <useModulePath>true</useModulePath>
    <argLine>--add-reads modfib=ALL-UNNAMED --add-exports modfib/pkgfib.internal=ALL-UNNAMED
             --add-opens modfib/pkgfib=ALL-UNNAMED --add-opens modfib/pkgfib.internal=ALL-UNNAMED</argLine>
  </configuration>
</plugin>

Note: This workaround hardcodes a single module name in classesDirectory, testClassesDirectory, and argLine. It does not scale to projects with multiple Java modules — each would need its own configuration, which is not possible with a single surefire execution.

Expected behavior

With Maven 4 Module Source Hierarchy and a module-info-patch.maven file, mvn test should work without any explicit surefire configuration beyond specifying the plugin version.

Working example

• Repository: https://github.com/aschemaven/java9-jigsaw-examples/tree/feature/surefire-whitebox/jigsaw-examples/example_test/m4
• First commit: workaround with surefire 3.5.5
• Second commit: zero-config with a locally patched surefire 3.6.0-SNAPSHOT (proof-of-concept, all 838 surefire-common tests passing)

Related issues

• [SUREFIRE-1755] Put dependencies from module-info in test sources on module path #3090 (SUREFIRE-1755) — Put dependencies from module-info in test sources on module path
• [SUREFIRE-1765] target/test-classes should not be added to classpath when tests run on modulepath using patch-module #3088 (SUREFIRE-1765) — target/test-classes should not be added to classpath when tests run on modulepath using patch-module
• [SUREFIRE-1811] Add resources to JPMS test module #3040 (SUREFIRE-1811) — Add resources to test module

[desruisseaux]

Thanks for looking at this! Do we have a link to the patch for Surefire 3.6.0-SNAPSHOT?

On a related topic, now that the JUnit 3 dependency is removed, are we ready to create a 4.0 branch? Or create a 3.x branch are target master as the development branch for 4.0?

[ascheman]

Thanks for looking at this! Do we have a link to the patch for Surefire 3.6.0-SNAPSHOT?

I will raise a PR soon but first wanted to do a little more testing.

On a related topic, now that the JUnit 3 dependency is removed, are we ready to create a 4.0 branch? Or create a 3.x branch are target master as the development branch for 4.0?

-> @olamy?

To implement the feature it should not be necessary to switch to Maven 4 API.

[ascheman]

Thanks for looking at this! Do we have a link to the patch for Surefire 3.6.0-SNAPSHOT?

I will raise a PR soon but first wanted to do a little more testing.

Intermediate status message, @desruisseaux: I wanted to add respective ITs which need to run with Maven 4. Unfortunately there is a (larger) number of other ITs which do not yet work with Maven 4. So I first have to investigate this.