Integrating Field Annotations into Protobuf Definitions

Developers seeking to utilize field annotations provided by GORM within their protobuf definitions may encounter challenges due to the absence of a native datetime type in Protobuf 3 syntax.

To address this, a post-processing script can be employed to augment the generated proto files with the desired GORM annotations. For example, given the following protobuf profile definition:

message Profile {
  uint64 id = 1;
  string name = 2;
  bool active = 3;
}

The following script ("gorm.sh") can be used for post-processing:

#!/bin/bash

g () {
  sed "s/json:\"$1,omitempty\"/json:\"$1,omitempty\" gorm:\"$2\"/"
}

cat $1 \
| g "id" "primary_key" \
| g "name" "varchar(100)" \
> $1.tmp && mv $1{.tmp,}

By invoking the script on the generated protobuf file (e.g., ./gorm.sh profile/profile.pb.go), the resulting output will be:

//...
type Profile struct {
    state         protoimpl.MessageState
    sizeCache     protoimpl.SizeCache
    unknownFields protoimpl.UnknownFields

    Id     uint64 `protobuf:"varint,1,opt,name=id,proto3" json:"id,omitempty" gorm:"type:primary_key"`
    Name   string `protobuf:"bytes,2,opt,name=name,proto3" json:"name,omitempty" gorm:"type:varchar(100)"`
    Active bool   `protobuf:"varint,3,opt,name=active,proto3" json:"active,omitempty"`
}
//...

This approach enables the integration of GORM field annotations into protobuf definitions without the need for custom implementations or third-party libraries.