[Django] #35766: Choice iterator breaks when using slices

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Sep 16, 2024, 9:29:28 AM9/16/24

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#35766: Choice iterator breaks when using slices
-----------------------+-----------------------------------------
Reporter: David | Type: Uncategorized
Status: new | Component: Uncategorized
Version: 5.0 | Severity: Normal
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-----------------------+-----------------------------------------
Currently the choice-iterator classes introduced in
https://code.djangoproject.com/ticket/24561 are designed to work with
index-based access.

{{{#!python

class MyModel(models.Model):
field = models.IntegerField(choices=lambda: range(10))

the_field = MyModel._meta.get_field("field")
the_field.choices[2]
#> 3
}}}

Since choices has been out for long time accepting there are libraries in
which the `field.choices` attribute was used as it it was a tuple/list,
which can be accessed also with slicing syntax (see [https://github.com
/sphinx-doc/sphinxcontrib-
django/blob/e9d43085ffc9b921fd7d880ff38d4e1d24d8d791/sphinxcontrib_django/docstrings/attributes.py#L123-L127
sphinxcontrib-django ]), this now raises an error:

{{{#!python
the_field.choices[:2]
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
Cell In[13], line 1
----> 1 the_field.choices[:2]

File /opt/venv/lib/python3.10/site-packages/django/utils/choices.py:24, in
BaseChoiceIterator.__getitem__(self, index)
23 def __getitem__(self, index):
---> 24 if index < 0:
25 # Suboptimally consume whole iterator to handle negative
index.
26 return list(self)[index]
27 try:
}}}

The
[https://docs.python.org/3.10/reference/datamodel.html?highlight=slicing#object.__getitem__
__getitem__] states that the management of key type should be handled in
the implementation.

It should be choosen if slices are going to be supported or if only
integers are going to be supported by this class.
--
Ticket URL: <https://code.djangoproject.com/ticket/35766>
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Sep 16, 2024, 9:32:26 AM9/16/24

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#35766: Choice iterator breaks when using slices

-------------------------------+--------------------------------------
Reporter: David | Owner: (none)

Type: Uncategorized | Status: new
Component: Uncategorized | Version: 5.0

Severity: Normal | Resolution:

Keywords: | 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 David:

Old description:

New description:

TypeError: '<' not supported between instances of 'slice' and 'int'

}}}

The
[https://docs.python.org/3.10/reference/datamodel.html?highlight=slicing#object.__getitem__
__getitem__] states that the management of key type should be handled in
the implementation.

It should be choosen if slices are going to be supported or if only
integers are going to be supported by this class.

--

--
Ticket URL: <https://code.djangoproject.com/ticket/35766#comment:1>

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Sep 17, 2024, 6:43:35 AM9/17/24

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#35766: Choice iterator breaks when using slices

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0

-------------------------------------+-------------------------------------
Changes (by Sarah Boyce):

* cc: Natalia Bidart, Nick Pope (added)
* component: Uncategorized => Database layer (models, ORM)
* has_patch: 0 => 1
* owner: (none) => Sarah Boyce
* stage: Unreviewed => Accepted
* status: new => assigned
* type: Uncategorized => Bug

Comment:

Thank you, replicated
I imagine we do want to support it (but I might be wrong) - made a small
patch
--
Ticket URL: <https://code.djangoproject.com/ticket/35766#comment:2>

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Sep 18, 2024, 10:45:47 AM9/18/24

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Keywords: | Triage Stage: Ready for
| checkin

Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Sarah Boyce):

* stage: Accepted => Ready for checkin

Comment:

PR received approval
--
Ticket URL: <https://code.djangoproject.com/ticket/35766#comment:3>

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Sep 18, 2024, 10:46:03 AM9/18/24

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#35766: Choice iterator breaks when using slices
-------------------------------------+-------------------------------------
Reporter: David | Owner: Sarah
| Boyce

Type: Bug | Status: closed

Component: Database layer | Version: 5.0
(models, ORM) |

Severity: Normal | Resolution: fixed

Changes (by Sarah Boyce <42296566+sarahboyce@…>):

* resolution: => fixed
* status: assigned => closed

Comment:

In [changeset:"ae1ee24178ecd53ac5ef3fc2055e4be8b9602ac9" ae1ee241]:
{{{#!CommitTicketReference repository=""
revision="ae1ee24178ecd53ac5ef3fc2055e4be8b9602ac9"
Fixed #35766 -- Handled slices in BaseChoiceIterator.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/35766#comment:4>

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Sep 19, 2024, 1:56:03 AM9/19/24

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Comment (by Claude Paroz):

Sarah, isn't this a regression in the last Django version that warrants a
backport?
--
Ticket URL: <https://code.djangoproject.com/ticket/35766#comment:5>

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Sep 19, 2024, 8:16:48 AM9/19/24

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Comment (by Natalia Bidart):

Replying to [comment:5 Claude Paroz]:

> Sarah, isn't this a regression in the last Django version that warrants
a backport?

Hey Claude, thanks for keeping an eye on things!
But the feature was introduced in 5.0 so it does not qualify for a
backport at this time.
--
Ticket URL: <https://code.djangoproject.com/ticket/35766#comment:6>

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Sep 19, 2024, 2:22:51 PM9/19/24

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Comment (by Claude Paroz):

Isn't the related commit 07fa79ef2bb3e8cace7bd87b292c6c85230eed05 ?
--
Ticket URL: <https://code.djangoproject.com/ticket/35766#comment:7>

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Sep 20, 2024, 3:13:00 AM9/20/24

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Comment (by Sarah Boyce):

Yes you're right - I missed this. I will create a release note a back port
shortly
--
Ticket URL: <https://code.djangoproject.com/ticket/35766#comment:8>

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Sep 20, 2024, 3:35:54 AM9/20/24

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#35766: Choice iterator breaks when using slices
-------------------------------------+-------------------------------------
Reporter: David | Owner: Sarah
| Boyce
Type: Bug | Status: closed
Component: Database layer | Version: 5.0
(models, ORM) |
Severity: Normal | Resolution: fixed
Keywords: | Triage Stage: Ready for
| checkin
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Sarah Boyce):

[https://github.com/django/django/pull/18604 PR] - have some questions as
to whether it is required for the backport
--
Ticket URL: <https://code.djangoproject.com/ticket/35766#comment:9>

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Sep 20, 2024, 9:02:56 AM9/20/24

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Comment (by Natalia Bidart):

I still think that this does not qualify for a backport:
07fa79ef2bb3e8cace7bd87b292c6c85230eed05 was landed in `main` right before
the 5.0 beta release, that means during the 5.0 alpha-beta phase. Thus, it
was backported to the `stable/5.0.x` branch due to the "alpha" backporting
policy. Therefore, this commit is really a "5.0 feature" and it's my
understanding that this does not qualify for a 5.1 backport.
--
Ticket URL: <https://code.djangoproject.com/ticket/35766#comment:10>

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