BooleanField not populated by obj if empty formdata given

[sergehauri]

The documentation on Form states:

obj – If formdata is empty or not provided, this object is checked for attributes matching form field names, which will be used for field values

However, with BooleanFields this isn't true: If formdata is empty, a BooleanField's data will be set to False, no matter what the value of obj is.

Actual Behavior

>>> import wtforms
>>> class F(wtforms.Form):
...     foo = wtforms.BooleanField()
... 
>>> class DummyObj:
...     def __init__(self):
...         self.foo = True
... 
>>> class DummyPostData(dict):
...     def getlist(self, key):
...         v = self[key]
...         if not isinstance(v, (list, tuple)):
...             v = [v]
...         return v
... 
>>> f = F(formdata=DummyPostData(), obj=DummyObj())
>>> f.foo.data
False
>>> f.foo.object_data
True

Expected Behavior

>>> f = F(formdata=DummyPostData(), obj=DummyObj())
>>> f.foo.data
True
>>> f.foo.object_data
True

Environment

• Python version: 3.8.0
• wtforms version: 2.3.3

[davidism]

Duplicate of #662, #402, or one of these.