Calling save_m2m() in UserCreationForm.save()

[Mark Gensler]

Hello all!

I noticed that when calling contrib.auth.forms.UserCreationForm.save(), self.save_m2m() is not called when commit=True.

This caused an issue in one of my projects which uses a custom User model with ManyToMany fields. Is this something that should be changed? I saw in the docs [1] that it is advised to extend UserCreationForm and UserChangeForm if using a custom User model.

A few reasons I see to add this step to the UserCreationForm.save() method:

• UserCreationForm is a subclass of ModelForm, which does call save_m2m() when commit=True.
• UserChangeForm does call save_m2m() as part of save(), because the save() method is not overloaded. This seems inconsistent!

The solution I'd propose is:

class UserCreationForm(forms.ModelForm):

    ...

    def save(self, commit=True):
        user = super().save(commit=False)
        user.set_password(self.cleaned_data["password1"])
        if commit:
            user.save()

            if hasattr(self, "save_m2m"):

                self.save_m2m()

        return user

I'd be happy to raise a ticket and work on a patch if this change would be useful.

Thanks

Mark

[1] https://docs.djangoproject.com/en/dev/topics/auth/customizing/#custom-users-and-the-built-in-auth-forms

[Adam Johnson]

Your proposal seems reasonable - if actually saving, we should save the m2m fields too.

I think the best next step would be to file a ticket and work on a PR. The first step would be to add a test case reproducing the issue.

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[Mark Gensler]

Hi Adam, thanks for the reply. I'll open a ticket and start work on a PR. Mark