Better error message for missing trailing comma in ModelForm fields attribute

[Sachin Gupta]

I have the following ModelForm, that has a valid field body. 

class PostForm(ModelForm):

    class Meta:

        model = Post

        fields = ('body')

      

However when I validate the models, the following error comes up

django.core.exceptions.FieldError: Unknown field(s) (y, b, d, o) specified for Post

This is because the Django expects a 'list' in the fields attribute. The error can be solved by adding a trailing comma

fields = ('body',)

This problem is quite common, as people tend to forget the trailing comma. I have written a small hack for this problem, that throws the following error message if the trailing comma is missing

django.core.exceptions.FieldError: Missing trailing comma in fields attribute

This error message is more intuitive than the one that is thrown currently

Editions:

In django/forms/models.py

class ModelFormOptions(object):

    def __init__(self, options=None):

        self.model = getattr(options, 'model', None)

        self.fields = getattr(options, 'fields', None)

        self.exclude = getattr(options, 'exclude', None)

        self.widgets = getattr(options, 'widgets', None)

        if isinstance(self.fields,str):

            message = 'Missing trailing comma in fields attribute'

            raise FieldError(message)

        if isinstance(self.exclude,str):

            message = 'Missing trailing comma in exclude attribute'

            raise FieldError(message)

I am raising a FieldError but a TypeError could also be raised. 

Regards

Sachin Gupta

[Andre Terra]

I have a feeling that this is too much to ask from the framework, after all it shouldn't have to teach python, so I'm -0 on the proposed change.

Additionally, if users specify fields = 'body' with no parenthesis they would get the same error message and probably think "but I don't need a comma, it's just one field" or even write fields = 'body', which is just horrible..

Cheers,
AT

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