Idea: Use --module-source-path and --module for javac/javadoc/etc.

[tlinkowski]

Currently, we instrument javac and javadoc with --module-path and some other options, but we're not making use of --module-source-path. Such approach means that some references between module descriptors are not allowed although they should (compilation fails).

Example

module A {
  requires B;
}

module B {
  exports org.test.pkg to A;
}

Currently, Gradle will first try to compile B's module-info.java, but it will fail saying that it can't find module A.

With --module-source-path + --module (as suggested by @sormuras), we should be able to compile one module at a time (as we do now), but with the awareness of other modules before they're compiled.

Problems

1. To use --module-source-path, projects need to be in a layout where project dir name = module name. There's a convention for such naming (again, by @sormuras), but it's not widely used yet. Hence, this plugin would need to work for any kind of layout.

   • Potential solution: add a build-wide task that would copy all the module-info.java files into e.g. build/modules (all compileJava and javadoc tasks would need to depend on such a task).

[sormuras]

It would be sooo ... normal, if Gradle supported Java modules (including all related standard javac options) out of the box.