Migration revert

activerecord/CHANGELOG.md

@@ -1,5 +1,28 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Add Migration#revert
+
+    Can be used to revert migration commands or a whole migration.
+
+    For example, to create a revertible migration removing the table 'horses' and
+    creating the table 'apples':
+
+        class FixTenderloveMigration < ActiveRecord::Migration
+          def change
+            revert do
+              create_table(:horses) do |t|
+                t.text :content
+                t.datetime :remind_at
+              end
+            end
+            create_table(:apples) do |t|
+              t.string :variety
+            end
+          end
+        end
+
+    *Marc-André Lafortune*
+
 *   Fix AR#create to return an unsaved record when AR::RecordInvalid is
     raised. Fixes #3217.
 

activerecord/lib/active_record/migration.rb

@@ -368,22 +368,88 @@ def initialize(name = self.class.name, version = nil)
       @name       = name
       @version    = version
       @connection = nil
-      @reverting  = false
     end
 
     # instantiate the delegate object after initialize is defined
     self.verbose  = true
     self.delegate = new
 
-    def revert
-      @reverting = true
-      yield
-    ensure
-      @reverting = false
+    # 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
+    # on the way down.
+    #
+    #   class FixTLMigration < ActiveRecord::Migration
+    #     def change
+    #       revert do
+    #         create_table(:horses) do |t|
+    #           t.text :content
+    #           t.datetime :remind_at
+    #         end
+    #       end
+    #       create_table(:apples) do |t|
+    #         t.string :variety
+    #       end
+    #     end
+    #   end
+    #
+    # Or equivalently, if +TenderloveMigration+ is defined as in the
+    # documentation for 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
+          recorder = CommandRecorder.new(@connection)
+          @connection = recorder
+          suppress_messages do
+            @connection.revert { yield }
+          end
+          @connection = recorder.delegate
+          recorder.commands.each do |cmd, args, block|
+            send(cmd, *args, &block)
+          end
+        end
+      end
     end
 
     def reverting?
-      @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
@@ -409,29 +475,9 @@ def migrate(direction)
 
       time   = nil
       ActiveRecord::Base.connection_pool.with_connection do |conn|
-        @connection = conn
-        if respond_to?(:change)
-          if direction == :down
-            recorder = CommandRecorder.new(@connection)
-            suppress_messages do
-              @connection = recorder
-              change
-            end
-            @connection = conn
-            time = Benchmark.measure {
-              self.revert {
-                recorder.inverse.each do |cmd, args|
-                  send(cmd, *args)
-                end
-              }
-            }
-          else
-            time = Benchmark.measure { change }
-          end
-        else
-          time = Benchmark.measure { send(direction) }
+        time = Benchmark.measure do
+          exec_migration(conn, direction)
         end
-        @connection = nil
       end
 
       case direction
@@ -440,6 +486,21 @@ def migrate(direction)
       end
     end
 
+    def exec_migration(conn, direction)
+      @connection = conn
+      if respond_to?(:change)
+        if direction == :down
+          revert { change }
+        else
+          change
+        end
+      else
+        send(direction)
+      end
+    ensure
+      @connection = nil
+    end
+
     def write(text="")
       puts(text) if verbose
     end
@@ -478,7 +539,7 @@ def method_missing(method, *arguments, &block)
       arg_list = arguments.map{ |a| a.inspect } * ', '
 
       say_with_time "#{method}(#{arg_list})" do
-        unless reverting?
+        unless @connection.respond_to? :revert
           unless arguments.empty? || method == :execute
             arguments[0] = Migrator.proper_table_name(arguments.first)
             arguments[1] = Migrator.proper_table_name(arguments.second) if method == :rename_table

activerecord/lib/active_record/migration/command_recorder.rb

@@ -16,35 +16,49 @@ class Migration
     class CommandRecorder
       include JoinTable
 
-      attr_accessor :commands, :delegate
+      attr_accessor :commands, :delegate, :reverting
 
       def initialize(delegate = nil)
         @commands = []
         @delegate = delegate
+        @reverting = false
+      end
+
+      def revert
+        @reverting = !@reverting
+        previous = @commands
+        @commands = []
+        yield
+      ensure
+        @commands = previous.concat(@commands.reverse)
+        @reverting = !@reverting
       end
 
       # record +command+. +command+ should be a method name and arguments.
       # For example:
       #
       #   recorder.record(:method_name, [:arg1, :arg2])
-      def record(*command)
-        @commands << command
+      #
+      def record(*command, &block)
+        if @reverting
+          @commands << inverse_of(*command)
+        else
+          @commands << (command << block)
+        end
       end
 
-      # Returns a list that represents commands that are the inverse of the
-      # commands stored in +commands+. For example:
+      # Returns the inverse of the given command
       #
-      #   recorder.record(:rename_table, [:old, :new])
-      #   recorder.inverse # => [:rename_table, [:new, :old]]
+      #   recorder.inverse_of(:rename_table, [:old, :new])
+      #    # => [:rename_table, [:new, :old]]
       #
       # This method will raise an +IrreversibleMigration+ exception if it cannot
-      # invert the +commands+.
-      def inverse
-        @commands.reverse.map { |name, args|
-          method = :"invert_#{name}"
-          raise IrreversibleMigration unless respond_to?(method, true)
-          send(method, args)
-        }
+      # invert the +command+.
+      #
+      def inverse_of(command, args)
+        method = :"invert_#{command}"
+        raise IrreversibleMigration unless respond_to?(method, true)
+        send(method, args)
       end
 
       def respond_to?(*args) # :nodoc:
@@ -53,9 +67,9 @@ def respond_to?(*args) # :nodoc:
 
       [: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].each do |method|
         class_eval <<-EOV, __FILE__, __LINE__ + 1
-          def #{method}(*args)          # def create_table(*args)
-            record(:"#{method}", args)  #   record(:create_table, args)
-          end                           # end
+          def #{method}(*args, &block)          # def create_table(*args, &block)
+            record(:"#{method}", args, &block)  #   record(:create_table, args, &block)
+          end                                   # end
         EOV
       end
       alias :add_belongs_to :add_reference

activerecord/test/cases/invertible_migration_test.rb

@@ -17,6 +17,17 @@ def change
       end
     end
 
+    class InvertibleRevertMigration < SilentMigration
+      def change
+        revert do
+          create_table("horses") do |t|
+            t.column :content, :text
+            t.column :remind_at, :datetime
+          end
+        end
+      end
+    end
+
     class NonInvertibleMigration < SilentMigration
       def change
         create_table("horses") do |t|
@@ -40,6 +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")
@@ -67,6 +95,64 @@ def test_migrate_down
       assert !migration.connection.table_exists?("horses")
     end
 
+    def test_migrate_revert
+      migration = InvertibleMigration.new
+      revert = InvertibleRevertMigration.new
+      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
+
+    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"