Pare back default `index` option for the migration generator

- Using `references` or `belongs_to` in migrations will always add index
  for the referenced column by default, without adding `index:true` option
  to generated migration file.
- Users can opt out of this by passing `index: false`.
- Legacy migrations won't be affected by this change. They will continue
  to run as they were before.
- Fixes #18146

1 files changed, 5 insertions, 5 deletions

diff --git a/activerecord/test/cases/migration/references_statements_test.rb b/activerecord/test/cases/migration/references_statements_test.rb
index f613fd66c3..b9ce6bbc55 100644
--- a/activerecord/test/cases/migration/references_statements_test.rb
+++ b/activerecord/test/cases/migration/references_statements_test.rb
@@ -30,14 +30,14 @@ module ActiveRecord
         assert column_exists?(table_name, :taggable_type, :string)
       end
 
-      def test_creates_reference_id_index
-        add_reference table_name, :user, index: true
-        assert index_exists?(table_name, :user_id)
+      def test_does_not_create_reference_id_index_if_index_is_false
+        add_reference table_name, :user, index: false
+        assert_not index_exists?(table_name, :user_id)
       end
 
-      def test_does_not_create_reference_id_index
+      def test_create_reference_id_index_even_if_index_option_is_passed
         add_reference table_name, :user
-        assert_not index_exists?(table_name, :user_id)
+        assert index_exists?(table_name, :user_id)
       end
 
       def test_creates_polymorphic_index