Automatic modules and services

[Paul Bakker]

Hi,

I found an interesting issue with automatic modules that contain services. I have a small application that depends on jackson-core, jackson-databind and jackson-annotations.
As an experiment I started the app with only the jackson-databind jar file on the modulepath, which turns it into an automatic module. The application code, and the other two Jackson libs are still on the classpath.

	java -cp out:lib/jackson-annotations-2.7.3.jar:lib/jackson-core-2.7.3.jar -mp mods -addmods jackson.databind com.javamodularity.demonstrator.Demo
 
This gives the following exception:
	java.lang.module.ResolutionException: Module jackson.databind does not read a module that exports com.fasterxml.jackson.core

This is surprising, because jackson-databind is an automatic module, which should read the unnamed module. The unnamed module should contain jackson-core because it's on the classpath.
The real surprise is that this seems to be caused by jackson-databind having a service declaration in it's META-INF of type "com.fasterxml.jackson.core.ObjectCodec". It looks like an automatic module can't declare a service of a type declared in the unnamed module.
When I remove the service declaration from the jackson-databind JAR, it runs without exceptions. 

Is this a bug or desired behaviour? When placing jackson-core on the modulepath as well everything works as expected, but that's besides the point I think.

Best regards,

Paul Bakker