Add support to admin for expressions like (Lower('myfield'),) in model Meta.ordering

[Dutch Stiphout]

Similar to ticket #26257.

This DOES WORK in the views I've written, but when I try to access /admin/balfor/scheduledtransaction/ I get the same error as in the referenced ticket:

(Note that my app name is balfor, running Django version 2.0.4 final)

AttributeError at /admin/balfor/scheduledtransaction/
'Lower' object has no attribute 'startswith'

models.py:

from django.db import models
from django.db.models.functions import Lower

class ScheduledTransaction(models.Model):
    description = models.CharField(max_length=50, default="New Scheduled Transaction")
    period = models.CharField(max_length=2, default="1S")

    class Meta:
        ordering = ['period', Lower('description')]

admin.py:

admin.site.register(ScheduledTransaction)

[Claude Paroz]

I was able to reproduce.

[Nicolas Noé]

At first look, it seems the issue was previously discovered (https://code.djangoproject.com/ticket/28958), but the fix is incomplete (only solves for F() expressions, while the doc states "query expressions are supported".

[Carlton Gibson]

A couple of points:

First, I wondered why the existing test from the fix for #28958 didn't fail since it already uses Upper (​here):

     Upper(F('name')).asc(),

The key point is the asc() call, which returns an OrderBy (which then gets processed by ​the block added in the fix).

Remove the asc() call and the test fails with the error raised in get_ordering_field_columns().

The ordering works without the asc() call (or the F for that matter) so maybe get_ordering_field_columns() should call field.asc() (if available, when not already an OrderBy) in order to correct the behaviour here.

Second, whilst you can set an ordering including (say) Lower('description') on the model, if you try to set it on the ModelAdmin, the admin's ​`_check_ordering` check will error (in LOOKUP_SEP in field_name). This occurs in for the transform or OrderBy case. This check needs adjusting.

@Nicolas Noé Are you good to work on this ticket still?

[Nicolas Noé]

Sorry guys, I"ve been much more busy than expected lately. Deassigning the ticket now.

[Tim Graham]

​PR

[Tim Graham <timograham@…>]

In 0d8e3e6:

Fixed #29428 -- Fixed admin changelist crash when using a query expression without asc()/desc() in the ordering.

[Tim Graham <timograham@…>]

In ec2c9c35:

Refs #29428 -- Fixed admin check crash when using a query expression in ModelAdmin.ordering.

[Tim Graham <timograham@…>]

In a041161b:

[2.1.x] Fixed #29428 -- Fixed admin changelist crash when using a query expression without asc()/desc() in the ordering.

Backport of 0d8e3e608ee9aab5076d497664aa97e0a29e523e from master

[Tim Graham <timograham@…>]

In 531a152:

[2.1.x] Refs #29428 -- Fixed admin check crash when using a query expression in ModelAdmin.ordering.

Backport of ec2c9c353113bb1db6e32ed3f0b6c28bc06ca2eb from master

[Tim Graham <timograham@…>]

In 4bccfac3:

[2.0.x] Fixed #29428 -- Fixed admin changelist crash when using a query expression without asc()/desc() in the ordering.

Backport of 0d8e3e608ee9aab5076d497664aa97e0a29e523e from master

[Tim Graham <timograham@…>]

In 83986af9:

[2.0.x] Refs #29428 -- Fixed admin check crash when using a query expression in ModelAdmin.ordering.

Backport of ec2c9c353113bb1db6e32ed3f0b6c28bc06ca2eb from master