-Xmodule was the original option in JDK 9 to compile code "as if" that code is part of the module specified to -Xmodule. The option has been superseded by extending --patch-module to support source locations.

This issue tracks removing the remnants of -Xmodule from JDK 9 before GA. to avoid it becoming an attractive nuisance. Specifically, the option was made hidden (now -XD-Xmodule) as part of the transition and this hidden option should be removed.