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
25227	Add utility method `get_updated_model()` to `ModelForm`	Javier Candeira	Javier Candeira	"Add utility method get_updated_model() to ModelForm

Additionally, add utility method get_updated_models() to FormSet

Rationale:

While doing the djangogirls tutorial, I noticed that ModelForm.save(commit=False) is given to newcomers as a reasonable way to acquire a form's populated model. This is an antipattern for several reasons:

  - It's counterintuitive. To a newcomer, it's the same as ``save(save=no)``. 
  - It's a leaky abstraction. Understanding it requires understanding that the save method does two things: a) prepare the model, and b) save it to the database.
  - It doesn't name its effect or return well.

All these problems are addressed in the current patch. Changes:

 - Implement ModelForm.get_updated_model()
 - Implement FormSet.get_updated_models()
 - Refactor ModelForm.save() and FormSet.save() to allow the above.
 - Both the tests and contrib.auth have been modified: any call to save(commit=False) for the purpose of obtaining a populated model has been replaced by get_updated_model(). Tests still pass, I'm confident it's a successful refactor.
- New tests have been added for the new methods in different contexts (from a ModelForm, from a FormSet, etc).
 - documentation has also been modified to showcase the new methods.

Notes:

Uses of ModelForm.save(commit=False) in the codebase have been left alone wherever it was used for its side effects and not for its return value.

The Djangogirls tutorial has a PR that depends on the changes in the present one:

https://github.com/DjangoGirls/tutorial/pull/450"	Cleanup/optimization	assigned	Forms	dev	Normal				Unreviewed	1	0	0	0	0	0