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

3 files changed, 10 insertions, 30 deletions

diff --git a/railties/test/generators/migration_generator_test.rb b/railties/test/generators/migration_generator_test.rb
index 80f284674d..46154b7db2 100644
--- a/railties/test/generators/migration_generator_test.rb
+++ b/railties/test/generators/migration_generator_test.rb
@@ -79,8 +79,8 @@ class MigrationGeneratorTest < Rails::Generators::TestCase
 
     assert_migration "db/migrate/#{migration}.rb" do |content|
       assert_method :change, content do |change|
-        assert_match(/remove_reference :books, :author, index: true/, change)
-        assert_match(/remove_reference :books, :distributor, polymorphic: true, index: true/, change)
+        assert_match(/remove_reference :books, :author/, change)
+        assert_match(/remove_reference :books, :distributor, polymorphic: true/, change)
       end
     end
   end
@@ -166,8 +166,8 @@ class MigrationGeneratorTest < Rails::Generators::TestCase
 
     assert_migration "db/migrate/#{migration}.rb" do |content|
       assert_method :change, content do |change|
-        assert_match(/add_reference :books, :author, index: true/, change)
-        assert_match(/add_reference :books, :distributor, polymorphic: true, index: true/, change)
+        assert_match(/add_reference :books, :author/, change)
+        assert_match(/add_reference :books, :distributor, polymorphic: true/, change)
       end
     end
   end
@@ -178,8 +178,8 @@ class MigrationGeneratorTest < Rails::Generators::TestCase
 
     assert_migration "db/migrate/#{migration}.rb" do |content|
       assert_method :change, content do |change|
-        assert_match(/add_reference :books, :author, index: true, null: false/, change)
-        assert_match(/add_reference :books, :distributor, polymorphic: true, index: true, null: false/, change)
+        assert_match(/add_reference :books, :author, null: false/, change)
+        assert_match(/add_reference :books, :distributor, polymorphic: true, null: false/, change)
       end
     end
   end
diff --git a/railties/test/generators/model_generator_test.rb b/railties/test/generators/model_generator_test.rb
index fb502ec0c5..814f4c050e 100644
--- a/railties/test/generators/model_generator_test.rb
+++ b/railties/test/generators/model_generator_test.rb
@@ -345,26 +345,6 @@ class ModelGeneratorTest < Rails::Generators::TestCase
     assert_match(/The name 'Object' is either already used in your application or reserved/, content)
   end
 
-  def test_index_is_added_for_belongs_to_association
-    run_generator ["account", "supplier:belongs_to"]
-
-    assert_migration "db/migrate/create_accounts.rb" do |m|
-      assert_method :change, m do |up|
-        assert_match(/index: true/, up)
-      end
-    end
-  end
-
-  def test_index_is_added_for_references_association
-    run_generator ["account", "supplier:references"]
-
-    assert_migration "db/migrate/create_accounts.rb" do |m|
-      assert_method :change, m do |up|
-        assert_match(/index: true/, up)
-      end
-    end
-  end
-
   def test_index_is_skipped_for_belongs_to_association
     run_generator ["account", "supplier:belongs_to", "--no-indexes"]
 
diff --git a/railties/test/generators/scaffold_generator_test.rb b/railties/test/generators/scaffold_generator_test.rb
index eb81ea3d0e..6f7a83cae0 100644
--- a/railties/test/generators/scaffold_generator_test.rb
+++ b/railties/test/generators/scaffold_generator_test.rb
@@ -14,8 +14,8 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
     assert_file "app/models/product_line.rb", /class ProductLine < ActiveRecord::Base/
     assert_file "test/models/product_line_test.rb", /class ProductLineTest < ActiveSupport::TestCase/
     assert_file "test/fixtures/product_lines.yml"
-    assert_migration "db/migrate/create_product_lines.rb", /belongs_to :product, index: true/
-    assert_migration "db/migrate/create_product_lines.rb", /references :user, index: true/
+    assert_migration "db/migrate/create_product_lines.rb", /belongs_to :product/
+    assert_migration "db/migrate/create_product_lines.rb", /references :user/
 
     # Route
     assert_file "config/routes.rb" do |route|
@@ -94,8 +94,8 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
     assert_file "app/models/product_line.rb", /class ProductLine < ActiveRecord::Base/
     assert_file "test/models/product_line_test.rb", /class ProductLineTest < ActiveSupport::TestCase/
     assert_file "test/fixtures/product_lines.yml"
-    assert_migration "db/migrate/create_product_lines.rb", /belongs_to :product, index: true/
-    assert_migration "db/migrate/create_product_lines.rb", /references :user, index: true/
+    assert_migration "db/migrate/create_product_lines.rb", /belongs_to :product/
+    assert_migration "db/migrate/create_product_lines.rb", /references :user/
 
     # Route
     assert_file "config/routes.rb" do |route|