ModelForm fields ordering when Meta.fields is set

[Luke Garner <dj-t@…>]

Field ordering is currently determined by the order the fields were originally defined in the model. However, if the user specifically defines the fields to use in Meta.fields, it's safe to assume that's the order the user wants the fields to be outputted in.

Right now, this is accomplished with:

class myForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super(myForm, self).__init__(*args, **kwargs)
        self.fields.keyOrder = self.Meta.fields #This line should be unnecessary
    class Meta:
        model = myModel
        fields = ['field_3', 'field_2', 'field_9']

The new version would just be:

class myForm(forms.ModelForm):
    class Meta:
        model = myModel
        fields = ['field_3', 'field_2', 'field_9']

[Gary Wilson]

Sounds like the right thing to do. It's even a TODO in the code comments :)

As far as the patch goes, assigning directly to keyOrder is not a good idea. IMO, keyOrder looks like it should be a private attribute. Anyway, by blindly assigning to keyOrder without checking to see if those keys exist in the SortedDict would cause bad things to happen.

[Gary Wilson]

We should put the fields in the correct order in the newforms/models.py code.

[Luke Garner <dj-t@…>]

As far as I'm aware, there's no way to change the order of a SortedDict other than directly editing keyOrder. I've added a new patch which checks to ensure the fields are in keyOrder before reassigning them. I'm not sure this is 100% necessary, though. If Meta.fields contains a field that isn't in the attrsbase_fields SortedDict, then the program is going to fail anyway.

Do you think the best approach is to put in a descriptive error message to raise, if Model.fields is incorrect?

[Luke Garner <dj-t@…>]

ModelField fields ordering (now with error handling)

[Luke Garner <dj-t@…>]

ModelField fields ordering (now with error handling)

[anonymous]

How about performing a set.difference between opts.fields and keyOrder? This way, the error message could return all of the erroneous fields instead of just the first one.

[James Bennett]

Duplicate of #5986, which has several proposals and recent activity.