Generator Flags for the Protoc Compiler

Protoc Compiler Invocation

Make sure to Install Twirp and Protobuf generators first.

The protoc compiler uses the flag --twirp_out to generate twirp.go files, and --go_out to generate .pb.go files. See Protobuf Docs for details on how to use the protoc compiler with --go-out, the Twirp flag --twirp_out supports the same parameters.

For example, invoke the protoc compiler with default parameters to generate code for rpc/haberdasher/service.proto:

protoc --go_out=. --twirp_out=. rpc/haberdasher/service.proto

Modifying imports

The protoc compiler invocation can include optional flags to set the import path to be used in generated code: --go_opt and --twirp_opt.

When working with multiple proto files that use import statements, protoc-gen-twirp uses the option go_package field in the .proto files to determine the import paths for imported message types. For example:

option go_package = "github.com/twitchtv/thisisanexample";

The import_prefix parameter can be passed to --twirp_out in order to prefix the generated import path with something.

$ PROTO_SRC_PATH=./
$ IMPORT_PREFIX="github.com/example/rpc/haberdasher"
$ protoc \
  --proto_path=$PROTO_SRC_PATH \
  --twirp_out=import_prefix=$IMPORT_PREFIX:$PROTO_SRC_PATH \
  --go_out=import_prefix=$IMPORT_PREFIX:$PROTO_SRC_PATH \
  $PROTO_SRC_PATH/rpc/haberdasher/service.proto

Alternatively, an import mapping parameter can be passed multiple times to --twirp_out in order to substitute the import path for a given proto file with something else. By passing the parameter multiple times you can build up a map of proto file to import path inside the generator.

This parameter should be used when one of your proto files imports a proto file from another package and you're not generating your code at the $GOPATH/src root.

For example, you could tell protoc-gen-twirp that rpcutil/empty.proto can be found at github.com/example/rpcutil by using Mrpcutil/empty.proto=github.com/example/rpcutil:

$ PROTO_SRC_PATH=./
$ IMPORT_MAPPING="rpcutil/empty.proto=github.com/example/rpcutil"
$ protoc \
  --proto_path=$PROTO_SRC_PATH \
  --twirp_out=M$IMPORT_MAPPING:$PROTO_SRC_PATH \
  --go_out=M$IMPORT_MAPPING:$PROTO_SRC_PATH \
  $PROTO_SRC_PATH/rpc/haberdasher/service.proto