id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
33040	BaseModelForm.is_valid() should document how it modifies the BaseModelForm.instance	Danang Rahmatullah	nobody	"`BasedModelForm` extends `BaseForm`. When `BaseModelForm().is_valid()` is called, its super is called which in turn calls `BaseForm.errors` (property method). The issue is when there are no errors (self._errors is None): `BaseForm` calls `full_clean()` which runs the `_post_clean()` hook defined in `BaseModelForm`, finally modifying `BaseModelForm.instance`.

Given the abstraction level of subclasses of `BaseModelForm` such as `forms.ModelForm`, it is very unreasonable to expect that a seemingly simple function like `is_valid()` to create such a big change to a property as important as `instance`. I hope this side-effect is clearly explained in the documentation or have the code refactored to separate the modifying effect of `is_valid()` function from the form validity check

{{{
#!python
# form.instance.myfield = False
form = MyModelForm(instance=myinstance, data={""myfield"": True})
# form.instance.myfield = False
form.is_valid()
# form.instance.myfield = True
}}}"	Uncategorized	closed	Documentation	3.2	Normal	invalid	BaseModelForm is_valid		Unreviewed	0	0	0	0	0	0