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Parser.parse adds "missing" to original_data #146

lafrech opened this issue Nov 29, 2016 · 2 comments


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commented Nov 29, 2016

When parsing input, parser.parse adds 'field': missing to original_data for every missing field. This happens only at first level, not in nested schema.

Hopefully, this test case will make this clearer:

from marshmallow import Schema, fields, validates_schema

from webargs.flaskparser import parser

class Location(Schema):

    city = fields.Str()
    country = fields.Str()

class User(Schema):

    name = fields.Str()
    location = fields.Nested(Location)

    def print_original_data(self, data, original_data):

    class Meta:
        strict = True

input_1 = {'name': 'Eric Cartman'}
input_2 = {'location': {'city': 'South Park'}}

# Via pure Marshmallow
# {'name': 'Eric Cartman'}
# {'location': {'city': 'South Park'}}

# Mock Flask request object
class Request():
    def __init__(self, args):
        self.args = args

req_1 = Request(input_1)
req_2 = Request(input_2)

# Via webargs
parser.parse(User, req_1, locations=['query'])
parser.parse(User, req_2, locations=['query'])
# {'location': <marshmallow.missing>, 'name': 'Eric Cartman'}
# {'location': {'city': 'South Park'}, 'name': <marshmallow.missing>}

AFAIKT, this should not happen. I'd expect original_data to be the same as when using pure Marshmallow.

I could fix this by modifying _parse_requestlike this:

            argdict = schema.fields
            parsed = {}
            for argname, field_obj in iteritems(argdict):
                parsed_value = self.parse_arg(argname, field_obj, req, locations)
                # If load_from is specified on the field, try to parse from that key
                if parsed_value is missing and field_obj.load_from:
                    parsed_value = self.parse_arg(field_obj.load_from, field_obj, req, locations)
                    argname = field_obj.load_from
                # Only add value if not missing
                if parsed_value is not missing:
                    parsed[argname] = parsed_value

Is this the correct thing to do?

lafrech added a commit to Nobatek/webargs that referenced this issue Nov 29, 2016


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commented Nov 29, 2016


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commented Jan 8, 2017

@lafrech Thank you for reporting this. This is a legitimate bug and I was able to reproduce it (thanks for the example).

I've created a PR with your fix in #147

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