Can Spine merge desc.ref files automatically?

[ndolhii]

I use Spine v1.6.0 and want to create an executable shadow jar from my application. I use Gradle and shadow plugin for this.
When I try to start the application from the shadow jar I get this exception:

io.spine.type.UnknownTypeException: No Java class found for the Protobuf message of type: spine.system.server.Mirror
        at io.spine.type.TypeName.lambda$type$0(TypeName.java:202)
        at java.util.Optional.orElseThrow(Optional.java:290)
        at io.spine.type.TypeName.type(TypeName.java:202)
        at io.spine.type.TypeName.genericDescriptor(TypeName.java:176)
        at io.spine.type.TypeName.messageDescriptor(TypeName.java:184)
        at io.spine.server.entity.EntityVisibility.of(EntityVisibility.java:114)
        at io.spine.server.entity.model.EntityClass.<init>(EntityClass.java:88)
        at io.spine.server.projection.model.ProjectionClass.<init>(ProjectionClass.java:53)
        at io.spine.server.projection.model.ProjectionClass.lambda$asProjectionClass$0(ProjectionClass.java:63)
        at io.spine.server.model.ClassMap.setEntry(ClassMap.java:108)
        at io.spine.server.model.ClassMap.get(ClassMap.java:88)
        at io.spine.server.model.Model.getClass(Model.java:194)
        at io.spine.server.model.ModelClass.get(ModelClass.java:52)
        at io.spine.server.projection.model.ProjectionClass.asProjectionClass(ProjectionClass.java:63)
        at io.spine.server.projection.ProjectionRepository.toModelClass(ProjectionRepository.java:291)
        at io.spine.server.projection.ProjectionRepository.toModelClass(ProjectionRepository.java:110)
        at io.spine.server.entity.Repository.entityModelClass(Repository.java:156)
        at io.spine.server.entity.Repository.entityClass(Repository.java:177)
        at io.spine.server.projection.ProjectionRepository.createStorage(ProjectionRepository.java:326)
        at io.spine.server.projection.ProjectionRepository.createStorage(ProjectionRepository.java:110)
        at io.spine.server.entity.Repository.storage(Repository.java:308)
        at io.spine.server.entity.Repository.open(Repository.java:281)
        at io.spine.server.entity.Repository.registerWith(Repository.java:217)
        at io.spine.server.entity.DefaultRecordBasedRepository.registerWith(DefaultRecordBasedRepository.java:77)
        at io.spine.server.entity.EventDispatchingRepository.registerWith(EventDispatchingRepository.java:70)
        at io.spine.server.projection.ProjectionRepository.registerWith(ProjectionRepository.java:146)
        at io.spine.server.BoundedContext.registerIfAware(BoundedContext.java:299)
        at io.spine.server.BoundedContext.register(BoundedContext.java:205)
        at io.spine.system.server.SystemContext.registerRepositories(SystemContext.java:85)
        at io.spine.system.server.SystemContext.newInstance(SystemContext.java:73)
        at io.spine.server.BoundedContextBuilder.buildPartial(BoundedContextBuilder.java:615)
        at io.spine.server.BoundedContextBuilder.buildPartial(BoundedContextBuilder.java:605)
        at io.spine.server.BoundedContextBuilder.buildSystem(BoundedContextBuilder.java:591)
        at io.spine.server.BoundedContextBuilder.build(BoundedContextBuilder.java:543)
        ...

A solution that solves this problem is to configure merging desc.ref files on the stage of assembling the shadow jar.
With the shadow plugin I use it looks like this:

shadowJar {
  mergeServiceFiles {
    path = 'desc.ref'
  }
}

Can Spine framework do something to let end-users avoid this manual configuration?

[dmdashenkov]

The feature of automatic descriptor merging may belong to bootstrap. In general, this might be a good idea. However, I think we would have to support many plugins, not only shadowJar.

[alexander-yevsyukov]

@dmdashenkov, what other plugins do you have in mind?

[dmdashenkov]

I suppose technologies like Spring, Micronault, cloud providers and such may provide their own merging tools.

[yuri-sergiichuk]

On the other hand, if we use unique names instead of desc, we'll not have to manage the merging. Just read all .ref you find and you're good to go, right?

[dmdashenkov]

Not having unique names and avoiding classpath scanning is the whole point of this file.

[dmdashenkov]

As a conclusion, we've decided to merge descriptor reference files automatically when possible. See this issue for details.