pyramid_swagger is not returning an easily parsable exception message

[tomelm]

trafficstars

I'm getting a RequestValidationError for a missing param but pyramid seems to be stringifying the error message:

ipdb> e
<RequestValidationError at 0x7f39c1cbeb88 400 Bad Request>
ipdb> e.__class__
<class 'pyramid_swagger.exceptions.RequestValidationError'>
ipdb> e.message
"phone is a required parameter.\n\nFailed validating 'required' in schema:\n    {'in': 'query',\n     'maxLength': 50,\n     'name': 'phone',\n     'required': True,\n     'type': 'string'}\n\nOn instance:\n    None"

I could do some kind of nasty string parsing to make this usable but that's not ideal. There doesn't appear to be any way to pull a well-formatted message

ipdb> e.args
("phone is a required parameter.\n\nFailed validating 'required' in schema:\n    {'in': 'query',\n     'maxLength': 50,\n     'name': 'phone',\n     'required': True,\n     'type': 'string'}\n\nOn instance:\n    None",)
ipdb> e.json
*** simplejson.scanner.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
ipdb> e.json_body
*** simplejson.scanner.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
ipdb> e.body
b''

[tomelm]

The main reason this is an issue is because it makes it impossible for me to programmatically determine which field failed validation. In the case where we're building APIs, if I can't tell which field failed I don't have a way to structure the failure message appropriately without simply passing back the entire message body (which is not valid ideal in the case where we're going from internal => external)

[gdchamal]

@tomelm did you find any solution ? I experimenting same issue when testing around parameter validation and a suitable json output structure

[ergo]

Bumping this, I will probably also run into this problem soon.

[ergo]

@gdchamal @tomelm, I've found that when you grab RequestValidationError it has child property that will return ValidationError from bravado that you can inspect for errors.

[ergo]

Here is an example (maybe a bit naive) implementation that shows how to return a json response with error information:

def exc_view(exc, request):
    error_info = exc.child
    for_json = {
        'message': getattr(error_info, 'message', u'{}'.format(error_info)),
        'validator': getattr(error_info, 'validator', None),
        'relative_schema_path': list(
            getattr(error_info, 'relative_schema_path', []))[:-1],
        'schema': getattr(error_info, 'schema', None),
        'relative_path': list(getattr(error_info, 'relative_path', [])),
        'instance': getattr(error_info, 'instance', None)
    }

    return for_json

config.add_exception_view(
    context='pyramid_swagger.exceptions.RequestValidationError',
    view=exc_view, renderer='json')

Example response:

{
  "message": "8 is not of type 'string'",
  "validator": "type",
  "relative_schema_path": [
    "properties",
    "city"
  ],
  "schema": {
    "type": "string",
    "example": "doggie"
  },
  "relative_path": [
    "city"
  ],
  "instance": 8
}

[ergo]

@striglia I think the issue can be closed, I could add the example to documentation.

[gdchamal]

thank you @ergo , I'll test your solution ASAP