How to send additional data in error response?

[thobson]

I'm probably missing something here but in my case the error responses don't match the format described by swagger.

For example:

u := usecase.NewInteractor(func(ctx context.Context, input TenancyInput, output *User) error {
  return status.Wrap(errors.New("record not found"), status.NotFound)
}
u.SetExpectedErrors(status.NotFound)

Generates swagger like this:

{
  "responses": {
    "404": {
     "description": "Not Found",
     "content": {
      "application/json": {
       "schema": {
        "$ref": "#/components/schemas/RestErrResponse"
       }
      }
     }
    }
   },
   "RestErrResponse": {
    "type": "object",
    "properties": {
     "code": {
      "type": "integer",
      "description": "Application-specific error code."
     },
     "context": {
      "type": "object",
      "additionalProperties": {},
      "description": "Application context."
     },
     "error": {
      "type": "string",
      "description": "Error message."
     },
     "status": {
      "type": "string",
      "description": "Status text."
     }
    }
   }
}

i.e status, error, code, context

But the server actually sends

{
  "status": "NOT_FOUND",
  "error": "not found: record not found"
}

Is there anyway I can also send a code and additional context in the response?

Thanks

[vearutop]

Context of error is extracted via rest.ErrWithFields.

type ErrWithFields interface {
	error
	Fields() map[string]interface{}
}

You can either implement your own structured error or use ctxd.NewError (external dependency).

[mtiller]

Am I correct in understanding that all errors generated by this framework will ultimately follow the ErrResponse schema? I see that there is a way to specify the schema associated with a "successful result". But is there no way to specify any other error schema besides ErrResponse? For example, support for RFC7807. It seems quite reasonable that an API developer would want to conform to RFC7807 but I don't see any way to do that here.

[vearutop]

ErrResponse is default structure for unsuccessful results, however any kind of structure can be used with a bit of instrumentation.

Please check an example, it sets up (*Handler).MakeErrResp to process use case errors.

Error content type can be customized with response.DefaultErrorResponseContentType.

	response.DefaultErrorResponseContentType = "application/problem+json"
	s := web.DefaultService()
......
	s.Wrap(
		func(handler http.Handler) http.Handler {
			var h *nethttp.Handler
			if nethttp.HandlerAs(handler, &h) {
				h.MakeErrResp = func(ctx context.Context, err error) (int, interface{}) {
					httpStatus, rfc7807Err := makeRFC7807Error(err) // Your custom error factory.
					
					return httpStatus, rfc7807Err
				}
			}

			return handler
		},
	)
.....
// Mount use case handlers.

If you land at a convenient and useful implementation of a RFC7807 error, please feel free to submit a PR with such a middleware, it may be helpful to other folks.