RequestParser support with custom validation function

[slitayem]

I have a custom validation function for a RequestParser argument. And I use the parser object to pass its arguments to spec. But unfortunately, it seems that the library does not support custom types input types e.g

    def one_character_string(value):
        """One character string parameter validator"""
        if isinstance(value, str) and len(value) == 1:
            return value
        else:
            raise ValueError(
                "The parameter '{}' should be a single character length".format(
                   value))

.....
    from flask_restful import reqparse
    parser = reqparse.RequestParser()
    parser.add_argument(
        'customInput', type=one_character_string,
        help='String value expected', required=False)

I am getting the following exception

File "/usr/local/lib/python3.5/dist-packages/flask_restful_swagger_2/init.py", line 271, in get_swagger_arg_type
elif issubclass(type, basestring):
TypeError: issubclass() arg 1 must be a class

[vsu]

You could try extending _get_swagger_arg_type in init.py to handle a custom argument and map it to swagger type 'object'.

https://swagger.io/docs/specification/data-models/data-types/

If you open a pull request I'd be happy to merge it.

[mycaule]

Do I have to use https://github.com/Yelp/bravado-core to validate the body request data for a POST route ?

I would like to reuse a model class MyRequestModel(Schema) I have written, I cannot find the code.

The class UserModel(Schema) in example is just for the response.