Consider the "snippet-files" directory currently under "src/java.base/share/classes/java/util/zip". That "snippet-files" directory is a standard location for placing snippets that may be used by the java.util.zip package in the java.base module. Currently that directory contains a Snippets.java file. It has been observed that the JDK build currently compiles classes under the "snippet-files" directory and even packages classes under that directory in the final generated module (java.base in this case). I verified this by checking the contents of java.base.jmod file.

I discussed this with Jon (from the javadoc team) and he noted that makefiles in our JDK build should be adjusted to ignore files in subdirectories that are not valid package names, like doc-files and snippet-files.