Hi Tim,

On 08/10/2015 11:07 AM, Tim Graham wrote:
> Yes, the idea is that ModelForm.save() method could become (after
> deprecation finishes):
> 
> def save(self):
>     """
>     Save this form's self.instance object and M2M data. Return the model
>     instance.
>     """
>     if self.errors:
>         raise ValueError(
>             "The %s could not be %s because the data didn't validate." % (
>                 self.instance._meta.object_name,
>                 'created' if self.instance._state.adding else 'changed',
>             )
>         )
>     self.instance.save()
>     self._save_m2m()
>     return self.instance
> 
> Instead of calling super().save(commit=False) to retrieve form.instance,
> you can just manipulate form.instance directly and then call
> super().save(). I don't see a need for the _instance getters/setters you
> proposed.
> 
> There's also a deprecation checklist to help when writing a patch:
> https://docs.djangoproject.com/en/1.8/internals/contributing/writing-code/submitting-patches/#deprecating-a-feature

IMO this is an example of the sort of low-value deprecation of a
widely-used API that gets people upset at us for wasting their time.

I agree that .save(commit=False) isn't the best or best-named API ever,
but it's been in Django since the beginning, it's _extremely_ widely
used, and (having taught Django classes to new users), I don't think it
ranks very high on the list of Django APIs that cause confusion in practice.

I wouldn't mind an update to the docs to recommend manipulating
`form.instance` and then calling `form.save()` (in place of `obj =
form.save(commit=False); obj.save(); form.save_m2m()`). I don't think
this requires any code changes; it's been true for a while (since
model-validation I think?) that the actual instance-updating happens
already in `_post_clean()`.

This could put us on the path toward an eventual deprecation of
`commit=False`, but I think we should be very slow to actually deprecate it.

Carl

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