SplitArrayField failed to validate because remove_trailing_nulls doesn't work properly

[Mohamad Nour Chawich]

I have this form

class CategoryForm(forms.ModelForm):
    filters = SplitArrayField(SlugField(required=False), required=False, size=10, remove_trailing_nulls=True)

When I try to submit it without any values it fails with the error: "Item 0 in the array did not validate:"
The reason is that on this line 181 in contrib.postgres.forms.array.py

            if null_index:
                cleaned_data = cleaned_data[:null_index]

Obviously in my case the null_index is 0, therefore the cleaned_data is returned as [u'', u'', u'', u'', u'', u'', u'', u'', u'', u''] which fails to look like an empty_values on line 1188 in db.models.base.py

[Tim Graham]

I tried to reproduce with a regression test but couldn't. Maybe I got something wrong. Could you check it and provide a failing test?

[Mohamad Nour Chawich]

The test you proposed will not fail because you checked for the wrong value

 self.assertEqual(form.cleaned_data, {'array': ['', '']})

You should have checked for an empty array instead as in

 self.assertEqual(form.cleaned_data, {'array': []})

Since all values are considered empty characters remove_trailing_nulls should result in an empty array. Not in an array that has empty values. Such an array doesn't pass the later check of the form here

line 1188 db.models.base.py

            # Skip validation for empty fields with blank=True. The developer
            # is responsible for making sure they have a valid value.
            raw_value = getattr(self, f.attname)
            if f.blank and raw_value in f.empty_values:
                continue

In this case the raw_value is [, ] while it should have been trimmed.

[Mohamad Nour Chawich]

I solved that by modifying the clean method of SplitArrayField

        if self.remove_trailing_nulls:
            null_index = None
            for i, value in reversed(list(enumerate(cleaned_data))):
                if value in self.base_field.empty_values:
                    null_index = i
                else:
                    break
            if null_index is not None:
                cleaned_data = cleaned_data[:null_index]
                errors = errors[:null_index]

as the 0 index is still a valid index and shouldn't falsify the trimming condition.

[Tim Graham]

Oh I see.

[Daniel Quattrociocchi]

I have a pull request to offer with the changes suggested from this ticket ​https://github.com/django/django/pull/6283.

[Tim Graham <timograham@…>]

In 91f87b8:

Fixed #26283 -- Fixed removal of trailing nulls for SplitArrayField.