#33114: StringAgg always fails on TextField
-------------------------------------+-------------------------------------
               Reporter:  Swen       |          Owner:  nobody
  Kooij                              |
                   Type:             |         Status:  new
  Uncategorized                      |
              Component:  Database   |        Version:  3.2
  layer (models, ORM)                |
               Severity:  Normal     |       Keywords:
           Triage Stage:             |      Has patch:  0
  Unreviewed                         |
    Needs documentation:  0          |    Needs tests:  0
Patch needs improvement:  0          |  Easy pickings:  0
                  UI/UX:  0          |
-------------------------------------+-------------------------------------
 Example:

 {{{#!python
 class MyModel(models.Model):
      name = models.TextField()

 list(MyModel.objects.annotate(names=StringAgg('name', ',')))
 }}}

 Results in the error:

 {{{
 django.core.exceptions.FieldError: Expression contains mixed types:
 TextField, CharField. You must set output_field.
 }}}

 There are two possible work-arounds:

 1. Derive from `StringAgg` and set the `output_field`:

        {{{#!python
        class TextStringAgg(StringAgg):
            output_field = TextField()
        }}}

 2. Wrap the expression in `ExpressionWrapper`:

        {{{#!python
        ExpressionWrapper(StringAgg('name', ','), output_field=TextField())
        }}}

 This seems to be a regression introduced in 3.2 as part of this change:
 
https://github.com/django/django/commit/1e38f1191de21b6e96736f58df57dfb851a28c1f

-- 
Ticket URL: <https://code.djangoproject.com/ticket/33114>
Django <https://code.djangoproject.com/>
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