Merge obj and data + access obj as an attribute

[augnustin]

Actual Behavior

Either have a UserForm(obj=user) or UserForm(request.form) but having a combination of both is not possible.

Expected Behavior

As forms can be partial instead of representing all the object's fields, it would be convenient to being able to access other attributes from the form.

IMHO the simplest would be to have UserForm(obj=user) in the GET page, and UserForm(request.form, obj=user) in the POST page. Fields would be merged with request.form data first, then obj attributes for the rest.

Also, this would require a form.obj getter which would return the obj, just like form.data/form.formData works.

Finally, this would be useful for the "protected" attribute feature ( #217 ) as one would not need to add fields that are here simply for display, as they are accessible through form.obj.protected_attribute in the template.

Hope it makes sense

Environment

• Python version: 3.9.5
• wtforms version: 2.3.3

[whb07]

This would seem like an opinion of explicit vs implicit, and which would be better, yes? Perhaps being explicit with the data passing, especially to POST/PUT/PATCH etc and creating/mutating leads to clearer outcomes. The reader of the source code can quickly understand what is happening and what steps are being performed rather than the implicit form which you are mentioning. What do you think?

[augnustin]

Hello @whb07,

Thanks for your return. I'm not sure I clearly understand your point, as I don't feel like this has to do with explicitness as far as I understand.

Say you have a User model, with attributes email, first_name, last_name and a UserForm with only first_name, last_name as email is not editable.

Nowhere in the UserForm the email attribute is accessible in the UserForm(request.form) (except by defining email as a readonly attribute, which is less secure), but I do need to read it (eg. to make last_name mandatory if email is present), so I'm locked.

I did monkey patch it:

class BaseForm(Form):

    def __init__(self, *args, **kwargs):
        self.obj = kwargs['obj'] if 'obj' in kwargs else None
        super(BaseForm, self).__init__(*args, **kwargs)

but it feels to me like this should be available by default. Shouldn't it?

[rcx1]

User contains all the data, Userform only editable data, to combine them up you can use Userform.populate(<prepopulated_user_object>).
If you want use validators, you can set them on the fly (ie add mandatory validator if email is present in edited record)

[azmeuk]

The suggest behavior is already working, although not consistently/reliably, but it goes against the idea #662 to keep either formdata or obj/data/default/kwargs.

>>> from werkzeug.datastructures import ImmutableMultiDict
>>> from wtforms import Form, StringField
>>> class UserForm(Form):
...     name = StringField()
...     email = StringField()
...     
>>> form = UserForm(
...     ImmutableMultiDict({"name": "Bob"}),
...     data={"name": "Alice", "email": "alice@example.com"},
... )
>>> assert form.name.data == "Bob"
>>> assert form.email.data == "alice@example.com"

We might go in the other direction with v4, but I wonder if there could this could be supported with an option though.