Nullable fields in json generated from protobuf file

Table of Contents

Native support

With grpc v2 for go, protofile’s optional option is supported, so you don’t need to import proto extensions anymore and use things like google.protobuf.StringValue.

my.proto

message FeeView {
    optional string name = 1 [json_name = "name"];
}

message FeeView {

optional string name = 1 [json_name = "name"];

}

go mapper

var name *string
if fee.Name != nil {
	name = &fee.Name
}

fee := &desc.FeeView{
	Name: name,
}

var name *string

if fee.Name != nil {

name = &fee.Name

}

fee := &desc.FeeView{

Name: name,

}

Legacy way with extensions

Null for nil value

my.proto

import "google/protobuf/wrappers.proto";

message FeeView {
    google.protobuf.StringValue name = 1 [json_name = "name"];
}

import "google/protobuf/wrappers.proto";

message FeeView {

google.protobuf.StringValue name = 1 [json_name = "name"];

}

go mapper

import "github.com/gogo/protobuf/types"

var name *types.StringValue
if fee.Name != nil {
	name = &types.StringValue{
		Value: *fee.Name,
	}
}

fee := &desc.FeeView{
	Name: name,
}

import "github.com/gogo/protobuf/types"

var name *types.StringValue

if fee.Name != nil {

name = &types.StringValue{

Value: *fee.Name,

}

fee := &desc.FeeView{

Name: name,

}

Which will lead to this json response

{"translation_key":"a fee","name":null,"value":5,"style":"body","text_color":"grey","tag":null}

1	{"translation_key":"a fee","name":null,"value":5,"style":"body","text_color":"grey","tag":null}

Omit a field with nil value

If you want to omit the field completely, you can use oneof approach

proto

message View {
    oneof subtitle {
        string oneof_string_subtitle = 1 [json_name = "subtitle"];
    }
}

message View {

oneof subtitle {

string oneof_string_subtitle = 1 [json_name = "subtitle"];

}

go mapper

var subtitle *desc.View_OneofStringSubtitle
if in.Subtitle != nil {
	subtitle = &desc.View_OneofStringSubtitle{
		OneofStringSubtitle: *in.Subtitle,
	}
}

return &desc.View{
	Subtitle: subtitle,
}

var subtitle *desc.View_OneofStringSubtitle

if in.Subtitle != nil {

subtitle = &desc.View_OneofStringSubtitle{

OneofStringSubtitle: *in.Subtitle,

}

return &desc.View{

Subtitle: subtitle,

}

More info on json options for grpc — https://blog.bullgare.com/2020/07/complete-list-of-swagger-options-to-protobuf-file/

Nullable fields in json generated from protobuf file

Native support

Legacy way with extensions

Null for nil value

Omit a field with nil value

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