Should rules_proto provide a rule to generate docs from .proto files

[Yannic]

Generating docs for Protobuf message/services is a common use-case, so it would be nice to provide a way to generate them. I'm a bit on the edge of whether this rule should be part of rules_proto or be part of another repo.

What do people think?

[sgammon]

@Yannic my vote would be yes. I just tried to get protoc-gen-doc to work with rules_proto, to accomplish this very feature, but I've been unable to figure out how to easily invoke it (i.e. proto_lang_toolchain seems meant for other purposes, so I've resorted to macros, which are tough w.r.t. transitive dependencies)

I think it would be awesome if documentation could be generated directly from a proto_library. The requirements for that invocation are largely the same: access to dependencies (including transitive), source access, etc.

[cdickson-sum]

@Yannic my vote would also be yes. My experience is largely the same as @sgammon.