[Django] #36930: Using a custom ModelChoices (not IntegerChoices or TextChoices) member as the default value of a model field doesn't select the default value in form's select

[Django]

#36930: Using a custom ModelChoices (not IntegerChoices or TextChoices) member as
the default value of a model field doesn't select the default value in
form's select
-------------------------------------+-------------------------------------
Reporter: Antoine Humbert | Type: Bug
Status: new | Component: Database
| layer (models, ORM)
Version: 6.0 | 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
-------------------------------------+-------------------------------------
This was triggered in the following forum post:
https://forum.djangoproject.com/t/default-for-choices-field-isnt-default-
in-admin-form/44189

As per the documentation and the **date** / **DateField** example (see
https://docs.djangoproject.com/en/6.0/ref/models/fields/#enumeration-
types), defining choices for a data type other than **int** or **str**
(e.g. float) should be :

{{{
class FactorChoices(float, models.Choices):
HALF = 0.5
SINGLE = 1
DOUBLE = 2
}}}

then, setting a default value for a field should use one of the
enumeration's member (as per the example from documentation:
`default=YearInSchool.FRESHMAN`). E.g.:

{{{
class SomeModel(models.Model):
factor = models.FloatField(choices=FactorChoices,
default=FactorChoices.SINGLE)
}}}


When using such definitions, the default value is not selected by default
in forms created for such model. This is bescause the `str()` of the
default value returns the string representation provided by `enum.Enum`
instead of the string representation from `float`.

I believe this is a regression in
https://github.com/antoinehumbert/django/commit/fe19b33e2f76045617067dd5123041ae4d3a91ee
where the `django.db.models.Choices.__str__` (which specifically called
`str(self.value)`) method was removed to the profit of making
`IntegerChoices` and `TextChoices` inherit from `enum.ReprEnum`).
Unfortunaltly, this dropped the initial `Choices.__str__` behaviour for
all other subclasses of `Choices`.

I think the fix is as simple as making `Choices` inherit from
`enum.ReprEnum` instead of `enum.Enum`.

I'm working on a PR.
--
Ticket URL: <https://code.djangoproject.com/ticket/36930>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

[Django]

#36930: Using a custom ModelChoices (not IntegerChoices or TextChoices) member as
the default value of a model field doesn't select the default value in
form's select
-------------------------------------+-------------------------------------

Reporter: Antoine Humbert | Owner: Antoine
| Humbert
Type: Bug | Status: assigned
Component: Database layer | Version: 6.0
(models, ORM) |
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
-------------------------------------+-------------------------------------

Changes (by Antoine Humbert):

* owner: (none) => Antoine Humbert
* status: new => assigned

--
Ticket URL: <https://code.djangoproject.com/ticket/36930#comment:1>

[Django]

#36930: Using a custom ModelChoices (not IntegerChoices or TextChoices) member as
the default value of a model field doesn't select the default value in
form's select
-------------------------------------+-------------------------------------
Reporter: Antoine Humbert | Owner: Antoine
| Humbert
Type: Bug | Status: assigned
Component: Database layer | Version: 6.0
(models, ORM) |
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 Antoine Humbert:

Old description:

New description:

This was triggered in the following forum post:
https://forum.djangoproject.com/t/default-for-choices-field-isnt-default-
in-admin-form/44189

As per the documentation and the **date** / **DateField** example (see
https://docs.djangoproject.com/en/6.0/ref/models/fields/#enumeration-
types), defining choices for a data type other than **int** or **str**
(e.g. float) should be :

{{{
class FactorChoices(float, models.Choices):
HALF = 0.5
SINGLE = 1
DOUBLE = 2
}}}

then, setting a default value for a field should use one of the
enumeration's member (as per the example from documentation:
`default=YearInSchool.FRESHMAN`). E.g.:

{{{
class SomeModel(models.Model):
factor = models.FloatField(choices=FactorChoices,
default=FactorChoices.SINGLE)
}}}


When using such definitions, the default value is not selected by default
in forms created for such model. This is bescause the `str()` of the
default value returns the string representation provided by `enum.Enum`
instead of the string representation from `float`.

I believe this is a regression in

https://github.com/django/django/commit/fe19b33e2f76045617067dd5123041ae4d3a91ee

where the `django.db.models.Choices.__str__` (which specifically called
`str(self.value)`) method was removed to the profit of making
`IntegerChoices` and `TextChoices` inherit from `enum.ReprEnum`).
Unfortunaltly, this dropped the initial `Choices.__str__` behaviour for
all other subclasses of `Choices`.

I think the fix is as simple as making `Choices` inherit from
`enum.ReprEnum` instead of `enum.Enum`.

I'm working on a PR.

--

--
Ticket URL: <https://code.djangoproject.com/ticket/36930#comment:2>