JDK defines the platform-independent module descriptor in $MODULE/share/classes/ module-info.java and specifies the platform-dependent module metadata in $MODULE/$OS/classes/module-info.java.extra.

The build will generate module-info.java under gensrc/$MODULE for the configuration that the JDK build targets.

The build also supports --import-modules to import modules into JDK build. With all these combinations of JDK builds, it's hard to validate any change in this build support. We should identify a set of useful tests (that may need to add new tests) for verifying gensrc/module-info.java to make it easy to catch issues when change is made in this area.