Inconsistent behavior in passing request fields to Schema.load (many=True vs many=False)

With 4.0.0 (and marshmallow 3.0.0b13):

class Sch(Schema):
    foo = fields.Str()

parser = FlaskParser()

req = Mock()
req.mimetype = 'application/json'

req.get_json = lambda *args, **kwargs: [{'extra': 1}]
with pytest.raises(UnprocessableEntity) as e:
    parser.parse(Foo(many=True), req=req, locations=('json', ))
assert e.value.exc.messages == {0: {'extra': ['Unknown field.']}}

req.get_json = lambda *args, **kwargs: {'extra': 1}
parser.parse(Foo(), req=req, locations=('json', ))

So the with many=True the extra key is actually passed to Schema.load() (which can then raise ValidationError because unknown defaults to RAISE) but with many=False it is passed onwards. I think it’s confusing.

#267 would fix this.

[lafrech]

Fixed.

from werkzeug.exceptions import UnprocessableEntity
from marshmallow import Schema, fields
from webargs.flaskparser import FlaskParser
from unittest.mock import Mock


class Foo(Schema):
    foo = fields.Str()

parser = FlaskParser()

req = Mock()
req.mimetype = 'application/json'

req.get_data = lambda *args, **kwargs: '[{"extra": 1}]'

# Both raise UnprocessableEntity
try:
    parser.parse(Foo(many=True), req=req, location='json')
except UnprocessableEntity:
    print('OK')
try:
    parser.parse(Foo(), req=req, location='json')
except UnprocessableEntity:
    print('OK')

[tuukkamustonen]

Just a minor “correction”:

The latter case, with many=False actually failed with just {"extra": 1} not [{"extra": 1}] (as in your code above).

But both those now raise error properly, so yeah it’s fixed.