Respect association overrides over trait-defined foreign keys (#1767)

* Ensure association overrides take precedence over trait-defined foreign keys

  In 6.5.5, changes related to PR #1709 introduced an unintended behavior
  where a trait-defined `*_id` could take precedence over an explicit
  association override. This could lead to inconsistency between the
  association and its foreign key.

* Update `AttributeAssigner#aliased_attribute?` to prioritize associations

  When an association override is provided (e.g., `user: user_instance`),
  the corresponding trait-defined foreign key is ignored, keeping the object
  graph consistent with Rails/ActiveRecord expectations. The fix preserves
  the intent of PR #1709 regarding attribute/attribute_id conflicts.

* Add regression specs

  - Association override wins over trait-defined foreign key
  - Trait-defined foreign key applies when no association override is present
  - Multiple foreign-key traits remain supported

Example:

  Before (6.5.5):
    FactoryBot.build(:post, :with_user_id_999, user: user).user_id # => 999

  After (this change; consistent with 6.5.4):
    FactoryBot.build(:post, :with_user_id_999, user: user).user_id # => user.id

Related: #1709, #1767

lib/factory_bot/attribute_assigner.rb

@@ -121,6 +121,10 @@ def aliased_attribute_names_to_ignore
     #       in the same factory.
     #
     def aliased_attribute?(attribute, override)
+      if association_names.include?(override) && attribute.alias_for?(override) && attribute.name != override
+        return true
+      end
+
       return false if attribute_names.include?(override)
 
       attribute.alias_for?(override)

spec/acceptance/attribute_aliases_spec.rb

@@ -272,5 +272,59 @@
       expect(user.response).to eq "new response"
       expect(user.response_id).to eq 13.75
     end
+
+    context "when association overrides trait foreign key" do
+      before do
+        define_model("User", name: :string)
+        define_model("Post", user_id: :integer, title: :string) do
+          belongs_to :user, optional: true
+        end
+
+        FactoryBot.define do
+          factory :user do
+            name { "Test User" }
+          end
+
+          factory :post do
+            association :user
+            title { "Test Post" }
+
+            trait :with_system_user_id do
+              user_id { 999 }
+            end
+
+            trait :with_user_id_100 do
+              user_id { 100 }
+            end
+
+            trait :with_user_id_200 do
+              user_id { 200 }
+            end
+          end
+        end
+      end
+
+      it "prefers association override over trait foreign key" do
+        user = FactoryBot.create(:user)
+        post = FactoryBot.build(:post, :with_system_user_id, user: user)
+
+        expect(post.user_id).to eq(user.id)
+        expect(post.user).to eq(user)
+      end
+
+      it "uses trait foreign key when no association override is provided" do
+        post = FactoryBot.build(:post, :with_system_user_id)
+
+        expect(post.user_id).to eq(999)
+      end
+
+      it "handles multiple traits with foreign keys correctly" do
+        user = FactoryBot.create(:user)
+        post = FactoryBot.build(:post, :with_user_id_100, :with_user_id_200, user: user)
+
+        expect(post.user_id).to eq(user.id)
+        expect(post.user).to eq(user)
+      end
+    end
   end
 end