Always prefer class types to query types when casting `group`

When `group` is used in combination with any calculation method, the
resulting hash uses the grouping expression as the key. Currently we're
incorrectly always favoring the type reported by the query, instead of
the type known by the class. This causes differing behavior depending on
whether the adaptor actually gives proper types with the query or not.
After this change, the behavior will be the same on all adaptors -- we
see if we know the type from the class, fall back to the type from the
query, and finally fall back to the identity type.

Fixes #25595

1 files changed, 6 insertions, 0 deletions

diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index cfae700159..06c2f10dc6 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -1,4 +1,5 @@
 require "cases/helper"
+require "models/book"
 require 'models/club'
 require 'models/company'
 require "models/contract"
@@ -793,4 +794,9 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal 50, result[1].credit_limit
     assert_equal 50, result[2].credit_limit
   end
+
+  def test_group_by_attribute_with_custom_type
+    Book.create!(status: :published)
+    assert_equal({ "published" => 1 }, Book.group(:status).count)
+  end
 end