#23405: Blank-able CharFields require default=''
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Reporter: yuvadm | Owner: coldmind
Type: Bug | Status: assigned
Component: Migrations | Version: 1.7
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by coldmind):
{{{
<truecoldmind> MarkusH, consider the field
models.CharField(max_length=100, null=True, blank=True). In that case
default after deconstruct will be empty string, this is not correct.
<truecoldmind> The check can be "if self.blank and not self.null and
self.default is NOT_PROVIDED"
<MarkusH> truecoldmind: what has blank to do with database default anyway?
<MarkusH> but I agree, you need to check for null
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<truecoldmind> I'm thinking due to
https://docs.djangoproject.com/en/dev/ref/models/fields/#null. Docs
recommends to not use `null=True` for char and text fields. It may not be
obvious that `blank=True` without `null` will give empty string, but, we
should definitely not set empty string as default if neither `blank` nor
the `null` was specified
<MarkusH> blank is only used for form validation, iirc
<truecoldmind> Yup. But, if no `blank` and `null` specified, user must
specify default by himself. We are now returned to South behavior (it sets
empty string if only `blank` was specified), but I don't know how to make
thing to be obvious
<MarkusH> truecoldmind: which turns us back to one of my previous
questions: Django's migrations are not equal to South's. Do we want to
have the same behavior here?
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#django-dev
<truecoldmind> MarkusH, it will be good (reasons are explained in
https://code.djangoproject.com/ticket/23405#comment:5). Due to
https://docs.djangoproject.com/en/dev/ref/models/fields/#blank, `blank`
is not necessarily associated with forms
<truecoldmind> So I think that check in deconstuct "if self.blank and not
self.null and self.default is NOT_PROVIDED" will be right
<MarkusH> truecoldmind: gnaah, sorry. Missed half the comment when reading
if before.
<MarkusH> not self.has_default() instead, right?
<MarkusH> but yes, that should work
<truecoldmind> MarkusH, okay, thanks for conversation. I will do more
research about how changes in deconstruct will affect migrations and
update PR later
<MarkusH> Thank you for tackling the issue
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/23405#comment:14>
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