Allow adding nonnamed expression indexes to be revertible

activerecord/CHANGELOG.md

@@ -1,3 +1,16 @@
+*   Allow adding nonnamed expression indexes to be revertible.
+
+    Fixes #40732.
+
+    Previously, the following code would raise an error, when executed while rolling back,
+    and the index name should be specified explicitly. Now, the index name is inferred
+    automatically.
+    ```ruby
+    add_index(:items, "to_tsvector('english', description)")
+    ```
+
+    *fatkodima*
+
 *   Only warn about negative enums if a positive form that would cause conflicts exists.
 
     Fixes #39065.

activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

@@ -1387,8 +1387,14 @@ module ActiveRecord
 
           checks = []
 
+          if !options.key?(:name) && column_name.is_a?(String) && /\W/.match?(column_name)
+            options[:name] = index_name(table_name, column_name)
+            column_names = []
+          else
+            column_names = index_column_names(column_name || options[:column])
+          end
+
           checks << lambda { |i| i.name == options[:name].to_s } if options.key?(:name)
-          column_names = index_column_names(column_name || options[:column])
 
           if column_names.present?
             checks << lambda { |i| index_name(table_name, i.columns) == index_name(table_name, column_names) }

activerecord/test/cases/invertible_migration_test.rb

@@ -18,6 +18,7 @@ module ActiveRecord
         create_table("horses") do |t|
           t.column :content, :text
           t.column :remind_at, :datetime
+          t.column :place_id, :integer
         end
       end
     end
@@ -198,6 +199,12 @@ module ActiveRecord
       end
     end
 
+    class RevertNonNamedExpressionIndexMigration < SilentMigration
+      def change
+        add_index :horses, "remind_at, place_id"
+      end
+    end
+
     class RevertCustomForeignKeyTable < SilentMigration
       def change
         change_table(:horses) do |t|
@@ -485,6 +492,20 @@ module ActiveRecord
       end
     end
 
+    def test_migrate_revert_add_index_without_name_on_expression
+      InvertibleMigration.new.migrate(:up)
+      RevertNonNamedExpressionIndexMigration.new.migrate(:up)
+
+      connection = ActiveRecord::Base.connection
+      assert connection.index_exists?(:horses, [:remind_at, :place_id]),
+             "index on remind_at and place_id should exist"
+
+      RevertNonNamedExpressionIndexMigration.new.migrate(:down)
+
+      assert_not connection.index_exists?(:horses, [:remind_at, :place_id]),
+             "index on remind_at and place_id should not exist"
+    end
+
     def test_up_only
       InvertibleMigration.new.migrate(:up)
       horse1 = Horse.create