ProtoYAML

Marshal and unmarshal Protocol Buffers as YAML. Provides fine-grained error details with file, line, column and snippet information.

Fully compatible with protojson.

Usage

package main

import (
  "log"

  "github.com/bufbuild/protoyaml-go"
)

func main() {
  // Marshal a proto message to YAML.
  yamlBytes, err := protoyaml.Marshal(
    &pb.MyMessage{
      MyField: "hello world",
    },
  )
  if err != nil {
    log.Fatal(err)
  }

  // Unmarshal a proto message from YAML.
  options := protoyaml.UnmarshalOptions{
    Path: "testdata/basic.proto3test.yaml",
  }
  var myMessage pb.MyMessage
  if err := options.Unmarshal(yamlBytes, &myMessage); err != nil {
    log.Fatal(err)
  }
}

ProtoYAML returns either nil or an error with a detailed message. For every error found in the file, the error message includes the file name (if Path is set on UnmarshalOptions), line number, column number, and snippet of the YAML that caused the error. For example, when unmarshalling the following YAML file:

values:
  - single_bool: true
  - single_bool: false
  - single_bool: 1
  - single_bool: 0
  - single_bool: "true"
  - single_bool: "false"
  - single_bool: True
  - single_bool: False
  - single_bool: TRUE
  - single_bool: FALSE
  - single_bool: yes
  - single_bool: no

The following errors are returned:

testdata/basic.proto3test.yaml:5:18: expected bool, got "1"
   5 |   - single_bool: 1
     | .................^
testdata/basic.proto3test.yaml:6:18: expected bool, got "0"
   6 |   - single_bool: 0
     | .................^
testdata/basic.proto3test.yaml:7:18: expected tag !!bool, got !!str
   7 |   - single_bool: "true"
     | .................^
testdata/basic.proto3test.yaml:8:18: expected tag !!bool, got !!str
   8 |   - single_bool: "false"
     | .................^
testdata/basic.proto3test.yaml:9:18: expected bool, got "True"
   9 |   - single_bool: True
     | .................^
testdata/basic.proto3test.yaml:10:18: expected bool, got "False"
  10 |   - single_bool: False
     | .................^
testdata/basic.proto3test.yaml:11:18: expected bool, got "TRUE"
  11 |   - single_bool: TRUE
     | .................^
testdata/basic.proto3test.yaml:12:18: expected bool, got "FALSE"
  12 |   - single_bool: FALSE
     | .................^
testdata/basic.proto3test.yaml:13:18: expected bool, got "yes"
  13 |   - single_bool: yes
     | .................^
testdata/basic.proto3test.yaml:14:18: expected bool, got "no"
  14 |   - single_bool: no
     | .................^

Only true and false are valid values for the single_bool field.

For more examples, see the internal/testdata directory.

Validation

ProtoYAML can integrate with external validation libraries such as Protovalidate to provide additional rich error information. Simply provide a Validator to the UnmarshalOptions:

package main

import (
  "log"

  "github.com/bufbuild/protoyaml-go"
  "github.com/bufbuild/protovalidate-go"
)

func main() {
  validator, err := protovalidate.NewValidator()
  if err != nil {
    log.Fatal(err)
  }

  var myMessage pb.MyMessage
  options := protoyaml.UnmarshalOptions{
    Path: "testdata/basic.proto3test.yaml",
    Validator: validator,
  }
  if err := options.Unmarshal(yamlBytes, &myMessage); err != nil {
    log.Fatal(err)
  }
}

The errors produced by the Validator will show up along side the ProtoYAML errors. For example:

testdata/validate.validate.yaml:4:18 cases[2].float_gt_lt: value must be greater than 0 and less than 10 (float.gt_lt)
   4 |   - float_gt_lt: 10.5
     | .................^

Status: Beta

ProtoYAML is not yet stable. However, the final shape is unlikely to change drastically—future edits will be somewhat minor.

Legal

Offered under the Apache 2 license