Always call setattr in FormField.populate

[antonstakhouski]

I'm writing a flask website that communicates with an API gateway using json. I wrote a some ORM models using python dataclasses that convert json to objects and vice versa and hide all data manipulation stuff.

The problem is that i could receive a nested json: {"foo": 42, "nested": {"bar": "baz"}}. And i map it to something like

@dataclass
class B(BaseModel):
    bar: str = None

@dataclass
class A(BaseModel):
    foo: str = None
    nested: dict = None
    
    @property
    def nested_(self):
          return B.from_dict(self.nested)
    
    @property
    def nested_(self, value):
        self.nested = value.to_dict

And form is:

class NestedForm(FlaskForm):
   bar = StringField('Bar')

class MyForm(FlaskForm):
   foo = StringField('Foo')
   nested_ = FormField(NestedForm, 'Nested')

In routes I have code like this:

def update_a():
    form = MyForm()
    if form.validate_on_submit:
         obj = A()
         form.populate_obj(obj)
         obj.save()

FormField will not modify obj.nested (it won't write temporary candidate object to obj attribute).

[azmeuk]

I played a bit with your patch and I could not find anything wrong with this.
@davidism any thougths on this?

[davidism]

Seems fine, go ahead and merge it when ready.