excluding transitive module

[Remi Forax]

----- Mail original -----
> De: "Jochen Theodorou" <blackdrag at gmx.org>
> À: "jigsaw-dev" <jigsaw-dev at openjdk.java.net>
> Envoyé: Mercredi 15 Avril 2020 08:55:00
> Objet: Re: excluding transitive module

> On 14.04.20 20:20, Remi Forax wrote:
>> Hi Jochen,
>> JPMS has no notion of of API and implementation of the same jar. It's a concept
>> of your build tool and not something JPMS knows.
>>
>> The notion of compilation dependencies and runtime dependencies is not a concept
>> of JPMS but a concept of your build tools.
>>
>> In term of JPMS, if you want to be able to use a jar at compile time and another
>> one at runtime,
>> both should have the same module name, in fact they should have exactly the same
>> module descriptor (the same module-info).
>>
>> So in term of dependency,
>> - for,Maven/Gradle, the compile dependency will use SharedAPI and the runtime
>> dependency SharedApiImpl
>> - for JPMS, both have the same module-info and if you want to depend on that
>> module, just require it.
>>
>>  From the Maven Central POV, obviously, you have two jars so they can not have
>>  the same arfifact ID (coordinate), but they contains the same
>>  module-info.class.
> 
> If the case is api and implementation and the same module name, then
> using the build tool to exclude the api dependency works.
> 
> If the module name is not the same I have not found a solution. It is a
> problem here because of shared packages.

as Alex said, this should be fixed by the maintainers of the jars, not you.

> 
> I found this being a problem btw with a lot of jee libraries.
> 
> Of course I can make my project require whatever, but if it is libraries
> I do not have under control things get a bit difficult without changing
> them. But changing them is not an action really well supported by any
> build tool I know.

For the Jakarta EE libraries, the main issue is that there are not many jars that has a module-info, so the default strategy to name the automatic module with the jar name fail here because an api an its implementations should have the same name.
Injecting the right module-info until your pull request is accepted is an escape hatch.

> 
> bye Jochen

Rémi