only option not working properly for nested fields.

[ananthasayana]

from marshmallow import Schema, fields
class Address:
    def __init__(self, street, country):
        self.street = street
        self.country = country

class User:
    def __init__(self, name, email, location):
        self.name = name
        self.email = email
        self.location = location

class Blog:
    def __init__(self, id, title, author):
        self.title = title
        self.id = id
        self.author = author

class AddressSchema(Schema):
    street = fields.String()
    country = fields.String()

class UserSchema(Schema):
    name = fields.String()
    email = fields.Email()
    location = fields.Nested(AddressSchema)

class BlogSchema(Schema):
    id = fields.Int()
    title = fields.String()
    author = fields.Nested(UserSchema, only=['location'])

address = Address(street='4 cross', country='myCountry')
user = User(name="Anantha", email="anantha@python.org", location=address)
blog = Blog(id = 1, title="nested only test", author=user)

print(BlogSchema(only=['title','author.location.street']).dump(blog))

Actual Result: {'title': 'nested only test', 'author': {}} Expected Result: {'title': 'nested only test', 'author': {'location': {'street': '4 cross'}}} Note: if I change author = fields.Nested(UserSchema, only=['location']) to author = fields.Nested(UserSchema, only=['location.street']) it works. But, This does not solve purpose as there may be many fields in location nested field and need different fields for different scenarios.

[juledwar]

I'm seeing the only= field completely ignored in my code. It dumps every single field in the nested object. We're working around it for now by using the exclude= instead but this obviously needs maintenance every time we change the nested schema.