Add query expression support for ModelAdmin list_display's admin_order_field

[Andreas Pelme]

Query expressions cannot currently be used with admin_order_field in a callable on list_display. The code expects a string and crashes when an query expression object is passed instead. This example shows the problem:

def full_name(obj):
    return f'{obj.first_name} {obj.last_name}'
my_callable.admin_order_field = Concat(F('first_name'), F('last_name'))

... which leads to a crash like this:

...
    self.queryset = self.get_queryset(request)
  File "/Users/andreas/code/django/django/contrib/admin/views/main.py", line 346, in get_queryset
    ordering = self.get_ordering(request, qs)
  File "/Users/andreas/code/django/django/contrib/admin/views/main.py", line 260, in get_ordering
    if order_field.startswith('-') and pfx == "-":
AttributeError: 'CombinedExpression' object has no attribute 'startswith'

It would make sense to be able to make use of all the nice stuff that has gone into query expression from the admin in this case! :)

[Tim Graham]

​PR

[Simon Wiles]

any chance of this getting committed? it would be very useful to have...

(specific use-case that drove me here: sorting in admin on a DateField that has NULLs...)

[Tim Graham <timograham@…>]

In e307ff29:

Fixed #27810 -- Allowed query expressions in admin_order_field.