[Django] #35314: Django 5 breaks value of Date field rendering correctly in template

[Django]

#35314: Django 5 breaks value of Date field rendering correctly in template
--------------------------------------+---------------------------
Reporter: Michael | Owner: nobody
Type: Bug | Status: new
Component: Forms | Version: 5.0
Severity: Normal | Keywords: form date
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
--------------------------------------+---------------------------
This used to work correctly in Django 4. Django 5 removed USE_L10N setting
from settings.py

When rendering an input field that is of type date:
{{{
/home/michael/.venv/project/lib/python3.11/site-
packages/django/forms/boundfield.py(108)as_widget()
-> return widget.render(
/home/michael/.venv/project/lib/python3.11/site-
packages/django/forms/widgets.py(279)render()
-> context = self.get_context(name, value, attrs)
/home/michael/.venv/project/lib/python3.11/site-
packages/django/forms/widgets.py(332)get_context()
-> context = super().get_context(name, value, attrs)
/home/michael/.venv/project/lib/python3.11/site-
packages/django/forms/widgets.py(271)get_context()
-> "value": self.format_value(value),
/home/michael/.venv/project/lib/python3.11/site-
packages/django/forms/widgets.py(555)format_value()
-> value, self.format or formats.get_format(self.format_key)[0]
}}}

We that ` formats.get_format(self.format_key)` only passes in 1 argument
to:

{{{
# django/utils/formats.py(109)get_format()

def get_format(format_type, lang=None, use_l10n=None):
"""
For a specific format type, return the format for the current
language (locale). Default to the format in the settings.
format_type is the name of the format, e.g. 'DATE_FORMAT'.

If use_l10n is provided and is not None, it forces the value to
be localized (or not), otherwise it's always localized.
"""
if use_l10n is None:
use_l10n = True
if use_l10n and lang is None:
lang = get_language()
format_type = str(format_type) # format_type may be lazy.
cache_key = (format_type, lang)
try:
return _format_cache[cache_key]
except KeyError:
pass
}}}

this means use_l10n initial value is `None`, which means it will be set to
True via the logic:
{{{
if use_l10n is None:
use_l10n = True
}}}

So then it sets a language, in my case `en-gb`, which makes results in a
`cache_key` of `('DATE_INPUT_FORMATS', 'en-gb')`

Which means the `get_format` method returns `['%d/%m/%Y', '%d/%m/%y',
'%Y-%m-%d']`
Which is really bad when `format_type = 'DATE_INPUT_FORMATS'`, because
HTML inputs must always be in the format `YYYY/MM/DD`, and hence selecting
the first format of `%d/%m/%Y` results in an error in your HTML template
when your input is rendered like `<input type="date" value="31/12/2024">`
instead of `<input type="date" value="2024/12/31">`


Not that it changes anything, but here is my `DATE_INPUT_FORMATS` from
settings.py (it has no `USE_L10N` setting as unfortunately that has been
removed):
{{{
DATE_INPUT_FORMATS = [
'%Y-%m-%d',
]
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/35314>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

[Django]

#35314: Django 5 breaks value of Date field rendering correctly in template

---------------------------+--------------------------------------

Reporter: Michael | Owner: nobody
Type: Bug | Status: new
Component: Forms | Version: 5.0

Severity: Normal | Resolution:

Keywords: form date | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0

---------------------------+--------------------------------------
Description changed by Michael:

Old description:

New description:

This used to work correctly in Django 4. Django 5 removed USE_L10N setting
from settings.py

When rendering an input field that is of type `date`:
{{{
/home/michael/.venv/project/lib/python3.11/site-
packages/django/forms/boundfield.py(108)as_widget()
-> return widget.render(
/home/michael/.venv/project/lib/python3.11/site-
packages/django/forms/widgets.py(279)render()
-> context = self.get_context(name, value, attrs)
/home/michael/.venv/project/lib/python3.11/site-
packages/django/forms/widgets.py(332)get_context()
-> context = super().get_context(name, value, attrs)
/home/michael/.venv/project/lib/python3.11/site-
packages/django/forms/widgets.py(271)get_context()
-> "value": self.format_value(value),
/home/michael/.venv/project/lib/python3.11/site-
packages/django/forms/widgets.py(555)format_value()
-> value, self.format or formats.get_format(self.format_key)[0]
}}}

We see that ` formats.get_format(self.format_key)` only passes in 1

--
Ticket URL: <https://code.djangoproject.com/ticket/35314#comment:1>

[Django]

#35314: Django 5 breaks value of Date field rendering correctly in template
---------------------------+--------------------------------------
Reporter: Michael | Owner: nobody

Type: Bug | Status: closed
Component: Forms | Version: 5.0
Severity: Normal | Resolution: duplicate

Keywords: form date | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
---------------------------+--------------------------------------

Changes (by David Sanders):

* resolution: => duplicate
* status: new => closed

Comment:

Duplicate of 35255
--
Ticket URL: <https://code.djangoproject.com/ticket/35314#comment:2>

[Django]

#35314: Django 5 breaks value of Date field rendering correctly in template
---------------------------+--------------------------------------
Reporter: Michael | Owner: nobody
Type: Bug | Status: closed
Component: Forms | Version: 5.0
Severity: Normal | Resolution: duplicate
Keywords: form date | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
---------------------------+--------------------------------------

Comment (by Michael):

In #35255 the author recommends passing in the value of
`settings.USE_L10N` ... which is deprecated. And in the thread you then
recommend setting `DATE_FORMAT`, as mentioned above I have set
`DATE_INPUT_FORMATS`, and they are not used.

Would you please care to explain why this issue is invalid?
--
Ticket URL: <https://code.djangoproject.com/ticket/35314#comment:3>

[Django]

#35314: Django 5 breaks value of Date field rendering correctly in template
---------------------------+--------------------------------------
Reporter: Michael | Owner: nobody
Type: Bug | Status: closed
Component: Forms | Version: 5.0
Severity: Normal | Resolution: duplicate
Keywords: form date | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
---------------------------+--------------------------------------

Comment (by David Sanders):

Yep you need to read the full comment:

> Have you tried setting the DATE_FORMAT in your custom language format
file as per: ​https://docs.djangoproject.com/en/5.0/topics/i18n/formatting
/#creating-custom-format-files ?

whereas you're using settings
--
Ticket URL: <https://code.djangoproject.com/ticket/35314#comment:4>

[Django]

#35314: Django 5 breaks value of Date field rendering correctly in template
---------------------------+--------------------------------------
Reporter: Michael | Owner: nobody
Type: Bug | Status: closed
Component: Forms | Version: 5.0
Severity: Normal | Resolution: duplicate
Keywords: form date | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
---------------------------+--------------------------------------

Comment (by Michael):

Replying to [comment:4 David Sanders]:

> Yep you need to read the full comment:
>
> > Have you tried setting the DATE_FORMAT in your custom language format
file as per: ​https://docs.djangoproject.com/en/5.0/topics/i18n/formatting
/#creating-custom-format-files ?
>
> whereas you're using settings

Thanks for the elaborating so I can try see it from your perspective. I
can set a custom language format file, but surely when it comes to the
HTML date value on forms, it should not depend on the language code, it
should *always* be `YYYY/MM/DD`, anything else is invalid. So is it not a
bug to make it depend on a custom format language code?
--
Ticket URL: <https://code.djangoproject.com/ticket/35314#comment:5>

[Django]

#35314: Django 5 breaks value of Date field rendering correctly in template
---------------------------+--------------------------------------
Reporter: Michael | Owner: nobody
Type: Bug | Status: closed
Component: Forms | Version: 5.0
Severity: Normal | Resolution: duplicate
Keywords: form date | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
---------------------------+--------------------------------------

Comment (by Natalia Bidart):

Hey Michael, in one of your comments, you describe your field as: `<input
type="date" value="31/12/2024">`. But Django doesn't use `type="date"` by
default (see as further reference #35293, #34853, #34660, #33113 and
more).

How are you generating this field?
--
Ticket URL: <https://code.djangoproject.com/ticket/35314#comment:6>

[Django]

#35314: Django 5 breaks value of Date field rendering correctly in template
---------------------------+--------------------------------------
Reporter: Michael | Owner: nobody
Type: Bug | Status: closed
Component: Forms | Version: 5.0
Severity: Normal | Resolution: duplicate
Keywords: form date | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
---------------------------+--------------------------------------

Comment (by Michael):

Hi Natalia, thanks for the comment, I am using it like this (which used to
work in Django 4):

{{{
class FooForm(forms.ModelForm):
class Meta:
model = Foo
exclude = [...]
widgets = {
`'bar_date': forms.DateInput(attrs={'type':'date'}),`
}
}}}

But I made the following changes to do it working:
`'bar_date': forms.DateInput(format='%Y-%m-%d',
attrs={'type':'date'}),`

Seems a bit counter intuitive to have a broken date input format by
default.
--
Ticket URL: <https://code.djangoproject.com/ticket/35314#comment:7>

[Django]

#35314: Django 5 breaks value of Date field rendering correctly in template
---------------------------+--------------------------------------
Reporter: Michael | Owner: nobody
Type: Bug | Status: closed
Component: Forms | Version: 5.0
Severity: Normal | Resolution: duplicate
Keywords: form date | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
---------------------------+--------------------------------------

Comment (by Natalia Bidart):

Replying to [comment:7 Michael]:

> Seems a bit counter intuitive to have a broken date input format by
default.

This feels a bit of a over statement, since Django does not support (yet)
`type="date"` input (see #21470). Were you able to read the related issues
I linked? This conversation is also quite relevant:
https://groups.google.com/g/django-developers/c/wp-pnzcB25o/m/D5gEOzPIAQAJ
--
Ticket URL: <https://code.djangoproject.com/ticket/35314#comment:8>

[Django]

#35314: Django 5 breaks value of Date field rendering correctly in template
---------------------------+--------------------------------------
Reporter: Michael | Owner: nobody
Type: Bug | Status: closed
Component: Forms | Version: 5.0
Severity: Normal | Resolution: duplicate
Keywords: form date | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
---------------------------+--------------------------------------

Comment (by Michael):

Replying to [comment:8 Natalia Bidart]:

> Replying to [comment:7 Michael]:
> > Seems a bit counter intuitive to have a broken date input format by
default.
>
> This feels a bit of a over statement, since Django does not support
(yet) `type="date"` input (see #21470). Were you able to read the related
issues I linked? This conversation is also quite relevant:
https://groups.google.com/g/django-developers/c/wp-pnzcB25o/m/D5gEOzPIAQAJ

Sorry, I should have toned it down and said the value being passed into
the date widgets is what doesn't work. The pattern that Django forms has
is quite a close relationship with HTML widgets. It's arguabley unexpected
the way that the `DateInput` is not an HTML `<input type="date">`. Thank
you for linking those conversations, sorry by the time I had answered the
question I forgot there were linked issues (kids handing off
arms/legs/calling for dinner time) and I lost track. Will checkout the
issues thanks!
--
Ticket URL: <https://code.djangoproject.com/ticket/35314#comment:9>