tree 526ee932993a4d1670762cb9fa6055b7534be87c
parent 9d397869d89256dc80a9a803c85ea7a8e9aba758
author Damien Neil <dneil@google.com> 1581579510 -0800
committer Damien Neil <dneil@google.com> 1584739332 +0000

compiler/protogen: add module= generator option

Add a generator option that strips a prefix from the generated
filenames.

Consider this case: We have google/protobuf/empty.proto, with a
go_package option of "google.golang.org/protobuf/types/known/emptypb".
We want to generate the code for this file, placing it into the
appropriate directory of our repository.

In the default mode used by the code generator (paths=import),
the generator outputs the file:

	google.golang.org/protobuf/types/known/emptypb/empty.pb.go

This is close to what we want, but has an unnecessary
"google.golang.org/protobuf/" prefix. In the GOPATH world, we could pass
--go_out=$GOPATH to protoc and get a generated file in the desired
location, but this path is not useful in the modules world.

The 'module' option allows us to strip off the module prefix, generating
the desired filename (types/known/emptypb/empty.pb.go):

	protoc --go_out=. --go_opt=module=google.golang.org/protobuf google/protobuf/empty.proto

The module name must be an exact, character-for-character match. This
matches protoc's file handling in general.

Default to and require the paths=import option when module= is
specified, since it only makes sense when combined with it.

Updates golang/protobuf#992.

Change-Id: Idbfe4826b6c0ece30d64dbc577131a4f16391936
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/219298
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>