Allow revert of whole migration [#8267]

activerecord/lib/active_record/migration.rb

@@ -379,7 +379,8 @@ def initialize(name = self.class.name, version = nil)
     self.verbose  = true
     self.delegate = new
 
-    # Reverses the migration commands for the given block.
+    # Reverses the migration commands for the given block and
+    # the given migrations.
     #
     # The following migration will remove the table 'horses'
     # and create the table 'apples' on the way up, and the reverse
@@ -399,9 +400,25 @@ def initialize(name = self.class.name, version = nil)
     #     end
     #   end
     #
-    # This command can be nested.
+    # Or equivalently, if +TenderloveMigration+ is defined as in the
+    # documentation for Migration:
     #
-    def revert
+    #   require_relative '2012121212_tenderlove_migration'
+    #
+    #   class FixupTLMigration < ActiveRecord::Migration
+    #     def change
+    #       revert TenderloveMigration
+    #
+    #       create_table(:apples) do |t|
+    #         t.string :variety
+    #       end
+    #     end
+    #   end
+    #
+    # This command can be nested.
+    def revert(*migration_classes)
+      run(*migration_classes.reverse, revert: true) unless migration_classes.empty?
+      if block_given?
         if @connection.respond_to? :revert
           @connection.revert { yield }
         else
@@ -415,12 +432,31 @@ def revert
             send(cmd, *args, &block)
           end
         end
+      end
     end
 
     def reverting?
       @connection.respond_to?(:reverting) && @connection.reverting
     end
 
+    # Runs the given migration classes.
+    # Last argument can specify options:
+    # - :direction (default is :up)
+    # - :revert (default is false)
+    def run(*migration_classes)
+      opts = migration_classes.extract_options!
+      dir = opts[:direction] || :up
+      dir = (dir == :down ? :up : :down) if opts[:revert]
+      if reverting?
+        # If in revert and going :up, say, we want to execute :down without reverting, so
+        revert { run(*migration_classes, direction: dir, revert: true) }
+      else
+        migration_classes.each do |migration_class|
+          migration_class.new.exec_migration(@connection, dir)
+        end
+      end
+    end
+
     def up
       self.class.delegate = self
       return unless self.class.respond_to?(:up)

activerecord/test/cases/invertible_migration_test.rb

@@ -51,6 +51,23 @@ def self.down
       end
     end
 
+    class RevertWholeMigration < SilentMigration
+      def initialize(name = self.class.name, version = nil, migration)
+        @migration = migration
+        super(name, version)
+      end
+
+      def change
+        revert @migration
+      end
+    end
+
+    class NestedRevertWholeMigration < RevertWholeMigration
+      def change
+        revert { super }
+      end
+    end
+
     def teardown
       if ActiveRecord::Base.connection.table_exists?("horses")
         ActiveRecord::Base.connection.drop_table("horses")
@@ -90,6 +107,52 @@ def test_migrate_revert
       assert !migration.connection.table_exists?("horses")
     end
 
+    def test_migrate_revert_whole_migration
+      migration = InvertibleMigration.new
+      [LegacyMigration, InvertibleMigration].each do |klass|
+        revert = RevertWholeMigration.new(klass)
+        migration.migrate :up
+        revert.migrate :up
+        assert !migration.connection.table_exists?("horses")
+        revert.migrate :down
+        assert migration.connection.table_exists?("horses")
+        migration.migrate :down
+        assert !migration.connection.table_exists?("horses")
+      end
+    end
+
+    def test_migrate_nested_revert_whole_migration
+      revert = NestedRevertWholeMigration.new(InvertibleRevertMigration)
+      revert.migrate :down
+      assert revert.connection.table_exists?("horses")
+      revert.migrate :up
+      assert !revert.connection.table_exists?("horses")
+    end
+
+    def test_revert_order
+      block = Proc.new{|t| t.string :name }
+      recorder = ActiveRecord::Migration::CommandRecorder.new(ActiveRecord::Base.connection)
+      recorder.instance_eval do
+        create_table("apples", &block)
+        revert do
+          create_table("bananas", &block)
+          revert do
+            create_table("clementines")
+            create_table("dates")
+          end
+          create_table("elderberries")
+        end
+        revert do
+          create_table("figs")
+          create_table("grapes")
+        end
+      end
+      assert_equal [[:create_table, ["apples"], block], [:drop_table, ["elderberries"]],
+                    [:create_table, ["clementines"], nil], [:create_table, ["dates"], nil],
+                    [:drop_table, ["bananas"]], [:drop_table, ["grapes"]],
+                    [:drop_table, ["figs"]]], recorder.commands
+    end
+
     def test_legacy_up
       LegacyMigration.migrate :up
       assert ActiveRecord::Base.connection.table_exists?("horses"), "horses should exist"