.proto ファイルの内容を parse した情報を protoc-gen-json (https://github.com/sourcegraph/prototools/blob/master/README.json.md) で dump

resources.proto

syntax = "proto3";
package resources;

message User {
  int32 id = 1;
  Profile profile = 2;
}

message Profile {
  int32 id = 1;
  string name = 2;
}

resources.proto.json

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}