Support descriptor_set_in protoc option

[rbbrns]

--descriptor_set_in=FILES Specifies a delimited list of FILES
each containing a FileDescriptorSet (a
protocol buffer defined in descriptor.proto).
The FileDescriptor for each of the PROTO_FILES
provided will be loaded from these
FileDescriptorSets. If a FileDescriptor
appears multiple times, the first occurrence
will be used.

This option cannot be used with --protop_path: "Only one of --descriptor_set_in and --proto_path can be specified."

[zpencer]

If the idea is to support both flags, the behavior is from the underlying protoc compiler, and the enhancement idea should be discussed there: protocolbuffers/protobuf#3973

Are you trying to use descriptor_set_in alone for the gradle plugin?

[rbbrns]

Sorry for not being more clear. I want to to be able to use descriptor_set_in from the gradle plugin. I was just documenting that descriptor_set_in and proto_path cannot be used together since it isn't clear from the descriptor_set_in documentation.

[tatemz]

I would much rather have this feature over copying my proto files across projects. Can we dig this issue back out of the 2018 Issue Graveyard? 😄

I have already started looking at the plugin source code but don't know gradle or groovy well enough to discern what types of changes to make.

I think we have to divide the problem into two parts:

1. Optionally using descriptor files as a gradle source set

   • We then use this source set to build a --descriptor_set_in flag (separated by commas I think)

2. When using descriptor sets, protoc still needs to know which files within the descriptor set to compile

   • This could be a string list 🤷‍♂️
   • Or this could be another source set, but if the source set is detected to be empty (which it would be when using a descriptor set), then the compile task is skipped (link).

Could really some suggestions from the repo owners on this one. 🙏

[friscoMad]

Any news on this?
It has been a long time and I see there was an attempt to add this in a PR 2 years ago, but seems that it was stalled.