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` and, 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. It returns a model, not a form.

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

 - Implement `ModelForm.get_updated_model()`
 - Implement `FormSet.get_updated_models()`
 - Refactor `models.py` minimally for the above to work.
 - Tests not added for `get_updated_model()` nor `get_updated_models()` because the changes are small enough to be considered as a refactoring.
 - 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`contrib.auth` have been modified: any call to `save(commit=False)` for the purpose of obtaining a populated model has been replaced by `get_updated_model()`.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.
 - `docs/customizing.txt` has also been modified to showcase the new method.

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 PR at https://github.com/DjangoGirls/tutorial/pull/450 depends on the present patch. Its changeset there explains the rationale for this addition better than anything else.
"	Cleanup/optimization	assigned	Forms	dev	Normal				Unreviewed	1	0	0	0	0	0