Partial loading on nested fields

Given an object with a nested field, is it possible to partially load the object and all nested fields? e.g.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
from marshmallow import Schema, fields


class Address(Schema):
    street = fields.Str(required=True)
    city = fields.Str(required=True)
    state = fields.Str(required=True)
    zipcode = fields.Str(required=True)
    country = fields.Str(required=True)


class User(Schema):
    first_name = fields.Str(required=True)
    last_name = fields.Str(required=True)
    address = fields.Nested(Address)


payload = {
    'first_name': 'John',
    'address': {
        'zipcode': '90210'
    }
}

user_schema = User()
data, errors = user_schema.load(payload, partial=True)
if errors:
    raise Exception(errors)

Output:

Traceback (most recent call last):
  File "test_partial_nested.py", line 30, in <module>
    raise Exception(errors)
Exception: {'address': {'city': ['Missing data for required field.'], 'state': ['Missing data for required field.'], 'street': ['Missing data for required field.'], 'country': ['Missing data for required field.']}}

Input is coming from a REST API and ideally I would like to bind all incoming payload at once.

Thanks!

[Finesse]

Wasn’t it fixed in #849?

@lafrech It hasn’t covered a case like this:

class Author(Schema):
    first_name = fields.Str(required=True)
    last_name = fields.Str(required=True)

class Book(Schema):
    author = fields.Nested(Author(partial=True), required=True)

Book().load({"author": {"last_name": "King"}}) # Undesired error

Here is my workaround for this case:

def partialSchema(schema_cls, **kwargs):
    schema = schema_cls(partial=True, **kwargs)
    for field in schema.fields.values():
        # This call doesn't make a side affect of changing the field object defined in the schema class
        field.required = False
    return schema

class Author(Schema):
    first_name = fields.Str(required=True)
    last_name = fields.Str(required=True)

class Book(Schema):
    author = fields.Nested(partialSchema(Author), required=True)

Book().load({"author": {"last_name": "King"}}) # No error

[Aeron]

I believe such a crucial caveat must be mentioned explicitly in the Schema documentation, regarding the partial parameter, because logically this parameter should work the same way even for a Schema instance wrapped by the Nested field.

Perhaps any Nested-related documentation also would be a suitable place for such a warning.

At the moment, this issue, except for source code digging, is the only way a developer may learn this parameter works like that.