protoc-gen-openapiv2: YAML output of examples is wrong

[nipeharefa]

🐛 Bug Report

Hello, this is my first issue, I just try using protoc-gen-openapiv2 and write some proto but I found when write the example of response and render it, the output will render []byte.

Sorry for my english.

To Reproduce

(Write your steps here:)

1. Write a example like this one:

examples: {
        key: "application/json"
        value: "{\"value\": \"the input value\"}"
      }

2. After generate, the value is like []byte:

My example proto

service Signup {
    rpc Signup (SignupRequest) returns (SampleResponse) {
      option (google.api.http) = {
        post: "/v1/signup",
        body: "*"
      };
      option (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_operation) = {
        consumes: [""]
        responses: {
            key: "200"
            value: {
                description: "Success"
            }
        }
        responses: {
            key: "500"
            value: {
                description: "internal Server Error",
                schema: {
                  json_schema: {
                    ref: ".Error";
                  }
                }
                examples: {
                  key: "application/json"
                  value: "{\"value\": \"the input value\"}"
                }
            }
        }
      };
    }
}

i;m using buf to generate, this is my configuration:

version: v1
managed:
  enabled: true
  go_package_prefix:
    default: github.com/example/example-proto
plugins:
  - remote: buf.build/grpc-ecosystem/plugins/openapiv2:v2.15.0
    opt:
      - merge_file_name=config
      - allow_merge
      - use_allof_for_refs
    out: ../../gen/openapiv2

[johanbrandhorst]

Hi, thanks for your issue! Looks like this is a special case for the application/json type: https://github.com/grpc-ecosystem/grpc-gateway/blob/257af994261d2395689810c48b3a3fb8ad7b318a/protoc-gen-openapiv2/internal/genopenapi/template.go#L2762C28-L2778. What does the swagger.json look like?

[nipeharefa]

hi @johanbrandhorst

paths:
  /_internal/user/{userId}:
    get:
      summary: Get tuples from the store that matches a query, without following userset rewrite rules
      operationId: GetUserByID
      responses:
        "200":
          description: A successful response.
          schema:
            $ref: '#/definitions/UserResponseInternal'
        "500":
          description: Internal Server Error
          schema:
            $ref: '#/definitions/Error'
          examples:
            application/json:
              - 123
              - 34
              - 118
              - 97
              - 108
              - 117
              - 101
              - 34
              - 58
              - 32
              - 34
              - 116
              - 104
              - 101
              - 32
              - 105
              - 110
              - 112
              - 117
              - 116
              - 32
              - 118
              - 97
              - 108
              - 117
              - 101
              - 34
              - 125
        default:
          description: An unexpected error response.
          schema:
            $ref: '#/definitions/rpcStatus'
      parameters:
        - name: userId
          in: path
          required: true
          type: string
      tags:
        - User

[johanbrandhorst]

Hm, that looks like YAML, I wonder if this is a problem with the yaml marshaler. Can you try to generate a JSON version?

[nipeharefa]

@johanbrandhorst you're right, i just change output to JSON, and look's good 👍 .

"get": {
        "summary": "Get tuples from the store that matches a query, without following userset rewrite rules",
        "operationId": "GetUserByID",
        "responses": {
          "200": {
            "description": "A successful response.",
            "schema": {
              "$ref": "#/definitions/UserResponseInternal"
            }
          },
          "500": {
            "description": "Internal Server Error",
            "schema": {
              "$ref": "#/definitions/Error"
            },
            "examples": {
              "application/json": {
                "value": "the input value"
              }
            }
          },
          "default": {
            "description": "An unexpected error response.",
            "schema": {
              "$ref": "#/definitions/rpcStatus"
            }
          }
        },
        "parameters": [
          {
            "name": "userId",
            "in": "path",
            "required": true,
            "type": "string"
          }
        ],
        "tags": [
          "User"
        ]
      }

[johanbrandhorst]

Great, that definitely narrows down the problem to the YAML output. The logic for this lives here:

grpc-gateway/protoc-gen-openapiv2/internal/genopenapi/format.go

Lines 33 to 37 in 257af99

	case FormatYAML:
	enc := yaml.NewEncoder(w)
	enc.SetIndent(2)
	return enc, nil

We may need to add some sort of workaround for json.RawMessage in the yaml marshaler. Thoughts @hedhyw?

[hedhyw]

@nipeharefa I've just fixed this in #3106, please try to use it from my branch and test it.