#36431: values() query on ForeignObject discards additional columns
-------------------------------------+-------------------------------------
     Reporter:  Jacob Walls          |                    Owner:  (none)
         Type:  Bug                  |                   Status:  new
    Component:  Database layer       |                  Version:  4.2
  (models, ORM)                      |
     Severity:  Normal               |               Resolution:
     Keywords:  composite primary    |             Triage Stage:  Accepted
  key                                |
    Has patch:  0                    |      Needs documentation:  0
  Needs tests:  0                    |  Patch needs improvement:  0
Easy pickings:  0                    |                    UI/UX:  0
-------------------------------------+-------------------------------------
Changes (by Simon Charette):

 * cc: Simon Charette (added)

Comment:

 On interesting dilemma we'll have to figure out here is what exactly to
 return when a foreign object composed of more than one `from_fields` is
 selected through `values` and `values_list`.

 With composite primary keys we've made usages of `values("pk")` turned
 into `values(Tuple(*pk_field_attnames))` and not
 `values(*pk_field_attnames)` so we should be coherent here IMO which means
 that we likely want something like

 {{{#!diff
 diff --git a/tests/composite_pk/test_values.py
 b/tests/composite_pk/test_values.py
 index 03a9a85496..cc45db40bc 100644
 --- a/tests/composite_pk/test_values.py
 +++ b/tests/composite_pk/test_values.py
 @@ -3,7 +3,7 @@

  from django.test import TestCase

 -from .models import Post, Tenant, User
 +from .models import Comment, Post, Tenant, User


  class CompositePKValuesTests(TestCase):
 @@ -210,3 +210,9 @@ def test_values(self):
                      {"pk": self.user_3.pk, "id": self.user_3.id},
                  ),
              )
 +
 +    def test_foreign_object_values(self):
 +        Comment.objects.create(id=1, user=self.user_1, integer=42)
 +        values = list(Comment.objects.values("user", "integer"))
 +        self.assertEqual(values[0]["user"], (self.user_1.tenant_id,
 self.user_1.id))
 +        self.assertEqual(values[0]["integer"], 42)
 }}}

 In other words I suggest we double down on making sure references to
 composite fields (the only two we support today is composite pk and
 foreign objects with multiple fields) in `values` and `values_list` return
 tuples instead of flattening them as we've taken this approach for
 `CompositePrimaryKey` (which is now part of the public API) and that
 `ForeignObject` is still private and has been broken since its
 introduction in this regard.
-- 
Ticket URL: <https://code.djangoproject.com/ticket/36431#comment:2>
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