go-protoparser 
go-protoparser is a yet another Go package which parses a Protocol Buffer file (proto2+proto3).
- Conforms to the exactly official spec.
- Undergone rigorous testing. The parser can parses all examples of the official spec well.
- Easy to use the parser. You can just call the Parse function and receive the Proto struct.
- If you don't care about the order of body elements, consider to use the unordered.Proto struct.
- Or if you want to use the visitor pattern, use the Visitor struct.
Installation
GO111MODULE=on go get github.com/yoheimuta/go-protoparser/v4
Example
A Protocol Buffer file versioned 3 which is an example of the official reference.
syntax = "proto3";
// An example of the official reference
// See https://developers.google.com/protocol-buffers/docs/reference/proto3-spec#proto_file
package examplepb;
import public "other.proto";
option java_package = "com.example.foo";
enum EnumAllowingAlias {
option allow_alias = true;
UNKNOWN = 0;
STARTED = 1;
RUNNING = 2 [(custom_option) = "this is a "
"string on two lines"
];
}
message outer {
option (my_option).a = true;
message inner { // Level 2
int64 ival = 1;
}
repeated inner inner_message = 2;
EnumAllowingAlias enum_field =3;
map<int32, string> my_map = 4;
}
service HelloService {
rpc SayHello (HelloRequest) returns (HelloResponse) {};
}The Parsed result is a Go typed struct. The below output is encoded to JSON for simplicity.
{
"Syntax": {
"ProtobufVersion": "proto3",
"ProtobufVersionQuote": "\"proto3\"",
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 0,
"Line": 1,
"Column": 1
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
"ProtoBody": [
{
"Name": "examplepb",
"Comments": [
{
"Raw": "// An example of the official reference",
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 19,
"Line": 2,
"Column": 1
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
{
"Raw": "// See https://developers.google.com/protocol-buffers/docs/reference/proto3-spec#proto_file",
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 59,
"Line": 3,
"Column": 1
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
}
],
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 151,
"Line": 4,
"Column": 1
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
{
"Modifier": 1,
"Location": "\"other.proto\"",
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 170,
"Line": 5,
"Column": 1
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
{
"OptionName": "java_package",
"Constant": "\"com.example.foo\"",
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 199,
"Line": 6,
"Column": 1
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
{
"EnumName": "EnumAllowingAlias",
"EnumBody": [
{
"OptionName": "allow_alias",
"Constant": "true",
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 269,
"Line": 8,
"Column": 5
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
{
"Ident": "UNKNOWN",
"Number": "0",
"EnumValueOptions": null,
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 300,
"Line": 9,
"Column": 5
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
{
"Ident": "STARTED",
"Number": "1",
"EnumValueOptions": null,
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 317,
"Line": 10,
"Column": 5
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
{
"Ident": "RUNNING",
"Number": "2",
"EnumValueOptions": [
{
"OptionName": "(custom_option)",
"Constant": "\"this is a string on two lines\""
}
],
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 334,
"Line": 11,
"Column": 5
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
}
],
"Comments": null,
"InlineComment": null,
"InlineCommentBehindLeftCurly": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 240,
"Line": 7,
"Column": 1
},
"LastPos": {
"Filename": "simple.proto",
"Offset": 454,
"Line": 14,
"Column": 1
}
}
},
{
"MessageName": "outer",
"MessageBody": [
{
"OptionName": "(my_option).a",
"Constant": "true",
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 476,
"Line": 16,
"Column": 5
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
{
"MessageName": "inner",
"MessageBody": [
{
"IsRepeated": false,
"IsRequired": false,
"IsOptional": false,
"Type": "int64",
"FieldName": "ival",
"FieldNumber": "1",
"FieldOptions": null,
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 544,
"Line": 18,
"Column": 7
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
}
],
"Comments": null,
"InlineComment": null,
"InlineCommentBehindLeftCurly": {
"Raw": "// Level 2",
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 527,
"Line": 17,
"Column": 23
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 509,
"Line": 17,
"Column": 5
},
"LastPos": {
"Filename": "simple.proto",
"Offset": 564,
"Line": 19,
"Column": 5
}
}
},
{
"IsRepeated": true,
"IsRequired": false,
"IsOptional": false,
"Type": "inner",
"FieldName": "inner_message",
"FieldNumber": "2",
"FieldOptions": null,
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 570,
"Line": 20,
"Column": 5
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
{
"IsRepeated": false,
"IsRequired": false,
"IsOptional": false,
"Type": "EnumAllowingAlias",
"FieldName": "enum_field",
"FieldNumber": "3",
"FieldOptions": null,
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 608,
"Line": 21,
"Column": 5
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
{
"KeyType": "int32",
"Type": "string",
"MapName": "my_map",
"FieldNumber": "4",
"FieldOptions": null,
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 645,
"Line": 22,
"Column": 5
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
}
],
"Comments": null,
"InlineComment": null,
"InlineCommentBehindLeftCurly": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 456,
"Line": 15,
"Column": 1
},
"LastPos": {
"Filename": "simple.proto",
"Offset": 676,
"Line": 23,
"Column": 1
}
}
},
{
"ServiceName": "HelloService",
"ServiceBody": [
{
"RPCName": "SayHello",
"RPCRequest": {
"IsStream": false,
"MessageType": "HelloRequest",
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 716,
"Line": 25,
"Column": 16
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
"RPCResponse": {
"IsStream": false,
"MessageType": "HelloResponse",
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 739,
"Line": 25,
"Column": 39
},
"LastPos": {
"Filename": "",
"Offset": 0,
"Line": 0,
"Column": 0
}
}
},
"Options": null,
"Comments": null,
"InlineComment": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 703,
"Line": 25,
"Column": 3
},
"LastPos": {
"Filename": "simple.proto",
"Offset": 757,
"Line": 25,
"Column": 57
}
}
}
],
"Comments": null,
"InlineComment": null,
"InlineCommentBehindLeftCurly": null,
"Meta": {
"Pos": {
"Filename": "simple.proto",
"Offset": 678,
"Line": 24,
"Column": 1
},
"LastPos": {
"Filename": "simple.proto",
"Offset": 759,
"Line": 26,
"Column": 1
}
}
}
],
"Meta": {
"Filename": "simple.proto"
}
}Usage
See also _example/dump.
func run() int {
flag.Parse()
reader, err := os.Open(*proto)
if err != nil {
fmt.Fprintf(os.Stderr, "failed to open %s, err %v\n", *proto, err)
return 1
}
defer reader.Close()
got, err := protoparser.Parse(reader)
if err != nil {
fmt.Fprintf(os.Stderr, "failed to parse, err %v\n", err)
return 1
}
gotJSON, err := json.MarshalIndent(got, "", " ")
if err != nil {
fmt.Fprintf(os.Stderr, "failed to marshal, err %v\n", err)
}
fmt.Print(string(gotJSON))
return 0
}
func main() {
os.Exit(run())
}Users
Motivation
There exists the similar protobuf parser packages in Go.
But I could not find the parser which just return a parsing result well-typed value. A parser which supports a visitor pattern is useful to implement like linter, but it may be difficult to use. It can be sufficient for most parsing situations to just return a parsing result well-typed value. This is easier to use.
Contributing
- Fork it
- Create your feature branch: git checkout -b your-new-feature
- Commit changes: git commit -m 'Add your feature'
- Pass all tests
- Push to the branch: git push origin your-new-feature
- Submit a pull request
License
The MIT License (MIT)
Acknowledgement
Thank you to the proto package: https://github.com/emicklei/proto
I referred to the package for the good proven design, interface and some source code.