nested.py

from marshmallow.fields import Nested as BaseNested


class Nested(BaseNested):
    """An overloaded Nested field that can handle more than a single schema.

    By giving it a list of schemas, it will iterate through them to find one
    that matches with the input data. It raises an error if the data doesn't
    correspond to any schema.
    """

    def _deserialize(self, value, attr, data):
        try:
            return super(Nested, self)._deserialize(value, attr, data)
        except ValueError:
            if isinstance(self.nested, list):
                for schema in self.nested:
                    if isinstance(schema, type):
                        schema = schema()
                    data, errors = schema.load(value)
                    if not errors:
                        return data
                self.fail("validator_failed")
            raise