This file is used by Groovy internally, there's no reason for the JDK to interpret its contents since it has only a meaning for Groovy. In short, it declares the list of extensions recognized by the Groovy compiler. That it prevents loading as a module is rather strange.

2017-12-03 16:37 GMT+01:00 Ceki Gulcu <ceki@qos.ch>:
Hi all,

Referring to a discussion on the maven users list [1], it appears that
removing the file META-INF/services/org.codehaus.groovy.source.Extensions from groovy-2.4.13.jar allows Java 9 to successfully load groovy-2.4.13.jar as an auto-module.

The org.codehaus.groovy.source.Extensions file contains the lone word "groovy" instead of a fully qualified class name.

Please advise.

Best regards,

--
Ceki Gülcü

[1] http://markmail.org/message/obdyvuv24kqpxm6v