only argument inconsistent between Nested(S, many=True) and List(Nested(S))

[rooterkyberian]

from pprint import pprint

from marshmallow import Schema
from marshmallow.fields import Integer, List, Nested, String


class Child(Schema):
    name = String()
    age = Integer()


class Family(Schema):
    children = List(Nested(Child))


class Family2(Schema):
    children = Nested(Child, many=True)

family = {'children':[
    {'name': 'Tommy', 'age': 12},
    {'name': 'Lily', 'age': 15},
]}

pprint(Family( only=['children.name']).dump(family).data)
pprint(Family2( only=['children.name']).dump(family).data)

returns

{'children': [{'age': 12, 'name': 'Tommy'}, {'age': 15, 'name': 'Lily'}]}
{'children': [{'name': 'Tommy'}, {'name': 'Lily'}]}

tested with marshmallow 2.15.4

The same applies to exclude argument.

[rooterkyberian]

For now I'm using following workaround:

class ListFix(List):
    @property
    def only(self):
        return getattr(self.container, 'only')

    @only.setter
    def only(self, new_options):
        original_options = getattr(self.container, 'only', ())
        if original_options:
            new_options &= type(new_options)(original_options)
        setattr(self.container, 'only', new_options)


class Child(Schema):
    name = String()
    age = Integer()


class Family(Schema):
    children = ListFix(Nested(Child))

the option propagation code was taken from BaseSchema.__apply_nested_option

maybe apply option code (the part I have copied to ListFix property) should be moved to field?

Edited: Just found a nasty side effect of my "fix"

family = {'children': [
    {'name': 'Tommy', 'age': 12},
    {'name': 'Lily', 'age': 15},
]}

for family_schema in (
        Family(),
        Family(only=['children.name']),
        Family2(),
        Family2(only=['children.name']),
):
    pprint(family_schema.dump(family).data)

prints

{'children': [{'name': 'Tommy'}, {'name': 'Lily'}]}
{'children': [{'name': 'Tommy'}, {'name': 'Lily'}]}
{'children': [{'age': 12, 'name': 'Tommy'}, {'age': 15, 'name': 'Lily'}]}
{'children': [{'name': 'Tommy'}, {'name': 'Lily'}]}

[sloria]

Thanks @rooterkyberian . Let's continue discussion of this in #779.