Add drop_join_table [#8267]

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

@@ -214,6 +214,17 @@ module ActiveRecord
         end
       end
 
+      # Drops the join table specified by the given arguments.
+      # See create_join_table for details.
+      #
+      # Although this command ignores the block if one is given, it can be helpful
+      # to provide one in a migration's +change+ method so it can be reverted.
+      # In that case, the block will be used by create_join_table.
+      def drop_join_table(table_1, table_2, options = {})
+        join_table_name = find_join_table_name(table_1, table_2, options)
+        drop_table(join_table_name)
+      end
+
       # A block for changing columns in +table+.
       #
       #  # change_table() yields a Table instance

activerecord/lib/active_record/migration/command_recorder.rb

@@ -73,6 +73,7 @@ module ActiveRecord
       [:create_table, :create_join_table, :change_table, :rename_table, :add_column, :remove_column,
         :rename_index, :rename_column, :add_index, :remove_index, :add_timestamps, :remove_timestamps,
         :change_column, :change_column_default, :add_reference, :remove_reference, :transaction,
+        :drop_join_table,
       ].each do |method|
         class_eval <<-EOV, __FILE__, __LINE__ + 1
           def #{method}(*args, &block)          # def create_table(*args, &block)
@@ -93,10 +94,12 @@ module ActiveRecord
         [:drop_table, [args.first]]
       end
 
-      def invert_create_join_table(args)
-        table_name = find_join_table_name(*args)
+      def invert_create_join_table(args, &block)
+        [:drop_join_table, args, block]
+      end
 
-        [:drop_table, [table_name]]
+      def invert_drop_join_table(args, &block)
+        [:create_join_table, args, block]
       end
 
       def invert_rename_table(args)

activerecord/test/cases/migration/command_recorder_test.rb

@@ -92,13 +92,19 @@ module ActiveRecord
       end
 
       def test_invert_create_join_table
-        drop_table = @recorder.inverse_of :create_join_table, [:musics, :artists]
-        assert_equal [:drop_table, [:artists_musics]], drop_table
+        drop_join_table = @recorder.inverse_of :create_join_table, [:musics, :artists]
+        assert_equal [:drop_join_table, [:musics, :artists], nil], drop_join_table
       end
 
       def test_invert_create_join_table_with_table_name
-        drop_table = @recorder.inverse_of :create_join_table, [:musics, :artists, table_name: :catalog]
-        assert_equal [:drop_table, [:catalog]], drop_table
+        drop_join_table = @recorder.inverse_of :create_join_table, [:musics, :artists, table_name: :catalog]
+        assert_equal [:drop_join_table, [:musics, :artists, table_name: :catalog], nil], drop_join_table
+      end
+
+      def test_invert_drop_join_table
+        block = Proc.new{}
+        create_join_table = @recorder.inverse_of :drop_join_table, [:musics, :artists, table_name: :catalog], &block
+        assert_equal [:create_join_table, [:musics, :artists, table_name: :catalog], block], create_join_table
       end
 
       def test_invert_rename_table

activerecord/test/cases/migration/create_join_table_test.rb

@@ -78,6 +78,48 @@ module ActiveRecord
 
         assert_equal [%w(artist_id music_id)], connection.indexes(:artists_musics).map(&:columns)
       end
+
+      def test_drop_join_table
+        connection.create_join_table :artists, :musics
+        connection.drop_join_table :artists, :musics
+
+        assert !connection.tables.include?('artists_musics')
+      end
+
+      def test_drop_join_table_with_strings
+        connection.create_join_table :artists, :musics
+        connection.drop_join_table 'artists', 'musics'
+
+        assert !connection.tables.include?('artists_musics')
+      end
+
+      def test_drop_join_table_with_the_proper_order
+        connection.create_join_table :videos, :musics
+        connection.drop_join_table :videos, :musics
+
+        assert !connection.tables.include?('musics_videos')
+      end
+
+      def test_drop_join_table_with_the_table_name
+        connection.create_join_table :artists, :musics, table_name: :catalog
+        connection.drop_join_table :artists, :musics, table_name: :catalog
+
+        assert !connection.tables.include?('catalog')
+      end
+
+      def test_drop_join_table_with_the_table_name_as_string
+        connection.create_join_table :artists, :musics, table_name: 'catalog'
+        connection.drop_join_table :artists, :musics, table_name: 'catalog'
+
+        assert !connection.tables.include?('catalog')
+      end
+
+      def test_create_join_table_with_column_options
+        connection.create_join_table :artists, :musics, column_options: {null: true}
+        connection.drop_join_table :artists, :musics, column_options: {null: true}
+
+        assert !connection.tables.include?('artists_musics')
+      end
     end
   end
 end