Fixes #33610

In order to avoid double assignments of nested_attributes for `has_many`
relations during record initialization, nested_attributes in `create_with`
should not be passed into `klass.new` and have them populate during
`initialize_internals_callback` with scope attributes.

However, `create_with` keys should always have precedence over where
clauses, so if there are same keys in both `create_with` and
`where_values_hash`, the value in `create_with` should be the one that's
used.

1 files changed, 12 insertions, 0 deletions

diff --git a/activerecord/test/cases/nested_attributes_test.rb b/activerecord/test/cases/nested_attributes_test.rb
index aa519fd332..bb1c1ea17d 100644
--- a/activerecord/test/cases/nested_attributes_test.rb
+++ b/activerecord/test/cases/nested_attributes_test.rb
@@ -217,6 +217,18 @@ class TestNestedAttributesInGeneral < ActiveRecord::TestCase
     mean_pirate.parrot_attributes = { name: "James" }
     assert_equal "James", mean_pirate.parrot.name
   end
+
+  def test_should_not_create_duplicates_with_create_with
+    Man.accepts_nested_attributes_for(:interests)
+
+    assert_difference("Interest.count", 1) do
+      Man.create_with(
+        interests_attributes: [{ topic: "Pirate king" }]
+      ).find_or_create_by!(
+        name: "Monkey D. Luffy"
+      )
+    end
+  end
 end
 
 class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase