Time-related _check_fix_default_value() methods can be optimized / simplified and have a bug

[Chris Jerdonek]

I noticed that three of the _check_fix_default_value() method definitions in django/db/models/fields/__init__.py can be simplified. Here is one of them: ​https://github.com/django/django/blob/fe074c96a343530beea50fbdd0803d3e7b739e8e/django/db/models/fields/__init__.py#L1156-L1167

For example, in each of them, timezone.now() is called even when the return value isn't needed / won't be used.

[Chris Jerdonek]

When I started looking at this, I noticed there is a bug on this line:
​https://github.com/django/django/blob/fe074c96a343530beea50fbdd0803d3e7b739e8e/django/db/models/fields/__init__.py#L2216

It can be triggered by the following when USE_TZ = True:

from django.db import models
import django.utils.timezone as timezone

class MyModel(models.Model):
    tz = models.TimeField(default=timezone.now().timetz())
    
    class Meta:
        app_label = 'test'

field = MyModel._meta.get_field('tz')
field.check()

It results in:

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/.../django/db/models/fields/__init__.py", line 1112, in check
    *self._check_fix_default_value(),
  File "/.../django/db/models/fields/__init__.py", line 2220, in _check_fix_default_value
    if lower <= value <= upper:
TypeError: '<=' not supported between instances of 'datetime.datetime' and 'datetime.time'

This case is not covered in the tests here:
​https://github.com/django/django/blob/fe074c96a343530beea50fbdd0803d3e7b739e8e/tests/invalid_models_tests/test_ordinary_fields.py#L743-L750

[Chris Jerdonek]

PR: ​https://github.com/django/django/pull/14717

[Mariusz Felisiak <felisiak.mariusz@…>]

In 542e7494:

Fixed #32966 -- Fixed TimeField.check() crash for timezone-aware times in default when USE_TZ = True.

[Mariusz Felisiak <felisiak.mariusz@…>]

In eebebfe0:

Refs #32966 -- Added _to_naive() and _get_naive_now() for use in DateTimeCheckMixin classes.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 6fa5d05d:

Refs #32966 -- Simplified the _check_fix_default_value() implementations.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 6f5e07a8:

Refs #32966 -- Refactored out DateTimeCheckMixin._check_if_value_fixed().

[Chris Jerdonek]

For future reference, it turns out the bug fixed by this ticket was previously mentioned here, but never opened as a separate ticket: https://code.djangoproject.com/ticket/21905#comment:19