Client: valid json response decode error: "{" expected: unexpected byte 34 '"'

[veqryn]

What version of ogen are you using?

v1.4.1

Can this issue be reproduced with the latest version?

Yes

What did you do?

Generated a golang client, used it, received an error, and ogen wasn't able to decode the error.

Here is the openapi spec that generated ogen's client:
https://github.com/veqryn/awesome-go-api/blob/c737ba1703d2ca30be0d898b17717eca8c70565f/protobufv3/openapiv3/gen/openapi.yaml#L248-L259

Here is the client that uses the generated code:
https://github.com/veqryn/awesome-go-api/blob/c737ba1703d2ca30be0d898b17717eca8c70565f/protobufv3/openapiv3/ogen/main.go#L48-L49

When I curl the server, the response looks like this:

$ curl -vv -k -L localhost:8080/error
* Host localhost:8080 was resolved.
* IPv6: ::1
* IPv4: 127.0.0.1
*   Trying [::1]:8080...
* Connected to localhost (::1) port 8080
> GET /error HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/8.7.1
> Accept: */*
>
* Request completely sent off
< HTTP/1.1 400 Bad Request
< Content-Type: application/json
< Date: Sat, 14 Sep 2024 06:05:49 GMT
< Content-Length: 306
<
* Connection #0 to host localhost left intact
{"code":3, "message":"This is an example error", "details":[{"@type":"type.googleapis.com/google.protobuf.Any", "value":{"@type":"type.googleapis.com/google.protobuf.DoubleValue", "value":224.92}}, {"@type":"type.googleapis.com/google.rpc.LocalizedMessage", "locale":"en-US", "message":"Fix your widget"}]}

Ogen seems to be unable to decode that response body into the rpcStatus object details.

What did you expect to see?

No decode error.

What did you see instead?

(*errors.wrapError)(0x140000b8b80)(decode response: default (code 400): decode application/json: decode RpcStatus: callback: decode field "details": callback: decode ProtobufAny: callback: decode field "locale": decode ProtobufAnyAdditionalItem: "{" expected: unexpected byte 34 '"' at 267)

[tdakkota]

protobufAny is defined as:

{
  "type": "object",
  "properties": {
    "@type": {
      "type": "string"
    }
  },
  "additionalProperties": {
    "type": "object" // <-- all properties should be objects except @type
  }
}

and input is:

{
  "@type": "type.googleapis.com/google.rpc.LocalizedMessage",
  "locale": "en-US", // <- string
  "message": "Fix your widget"
}

It seems for me that decoder works as intended. Error message might be more clear, I guess.

[veqryn]

Hm...

The yaml was created by the gRPC Gateway, which only supports OpenAPI v2:

  protobufAny:
    type: object
    properties:
      '@type':
        type: string
    additionalProperties: {}

I upgraded it to v3 using swagger-codegen, which turned it into this:

    protobufAny:
      type: object
      properties:
        '@type':
          type: string
      additionalProperties:
        type: object

So I'm not an expert in OpenAPI.

I am guessing that instead of additionalProperties: {} in the v2 yaml, it should be additionalProperties: true, is that correct?
Or is it a problem with the v2 -> v3 translation?

[tdakkota]

In OpenAPI 3, additionalProperties: {} is effectively the same as additionalProperties: true. It seems there is bug in swagger-codegen, it should not add type: object.

[veqryn]

Created issues here:
swagger-api/swagger-codegen#12468
OpenAPITools/openapi-generator#19596
grpc-ecosystem/grpc-gateway#4724

[veqryn]

@tdakkota thx. I've got a workaround/hack for this to generate the correct v3, but now I'm running into this issue/feature-request #1313