[Django] #30337: Django Admin - Migrations: default value for models.DateTime() with auto_add_now=True

[Django]

#30337: Django Admin - Migrations: default value for models.DateTime() with
auto_add_now=True
-----------------------------------------+------------------------
Reporter: jillesme | Owner: nobody
Type: Uncategorized | Status: new
Component: Uncategorized | Version: 2.2
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 |
-----------------------------------------+------------------------
Hello everyone,

In a personal project I created a model, populated the database and later
realised that I needed a `created` field on it. So I added
models.DateTime() with auto_add_now=True. When running the migrations I
got this prompt:

```
You are trying to add the field 'created' with 'auto_now_add=True' to
squad without a default; the database needs something to populate existing
rows.

1) Provide a one-off default now (will be set on all existing rows)
2) Quit, and let me add a default in models.py
Select an option: 1
Please enter the default value now, as valid Python
You can accept the default 'timezone.now' by pressing 'Enter' or you can
provide another value.
The datetime and django.utils.timezone modules are available, so you can
do e.g. timezone.now
Type 'exit' to exit this prompt
[default: timezone.now] >>>
You are trying to add the field 'created' with 'auto_now_add=True' to
squadapplication without a default; the database needs something to
populate existing rows.
// Now I had to run it again and do timezone.now() myself
```

I believe that the default should be `timezone.now()` (invoking the
function). When the default is `timezone.now` - without invoking it - it
will actually not work and not throw an error.

Is this a know bug or a feature? If it's a bug I'd like to contribute
myself to fix it :)

--
Ticket URL: <https://code.djangoproject.com/ticket/30337>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

[Django]

#30337: Django Admin - Migrations: default value for models.DateTime() with
auto_add_now=True

--------------------------------+--------------------------------------
Reporter: Jilles Soeters | Owner: nobody
Type: Uncategorized | Status: closed
Component: Migrations | Version: master
Severity: Normal | Resolution: worksforme

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 felixxm):

* status: new => closed
* resolution: => worksforme
* version: 2.2 => master
* component: Uncategorized => Migrations

Comment:

Migration works as expected in a described use case. When you leave
`timezone.now` as a default value then it will be added to a new
migration:
{{{
operations = [
migrations.AddField(
....
field=models.DateTimeField(auto_now_add=True,
default=django.utils.timezone.now),
)
]
}}}
and a new field in all existing rows will be filled by `timezone.now()`.

Please use one of
[https://code.djangoproject.com/wiki/TicketClosingReasons/UseSupportChannels
support channels], if you need further support.

--
Ticket URL: <https://code.djangoproject.com/ticket/30337#comment:1>