Support backwards compatible interface for migration down/up with rails 3.0.x.

activerecord/lib/active_record/migration.rb

@@ -329,6 +329,7 @@ module ActiveRecord
     end
 
     def self.method_missing(name, *args, &block) # :nodoc:
+      self.delegate = self.new
       (delegate || superclass.delegate).send(name, *args, &block)
     end
 

activerecord/test/cases/invertible_migration_test.rb

@@ -27,6 +27,19 @@ module ActiveRecord
       end
     end
 
+    class LegacyMigration < ActiveRecord::Migration
+      def self.up
+        create_table("horses") do |t|
+          t.column :content, :text
+          t.column :remind_at, :datetime
+        end
+      end
+
+      def self.down
+        drop_table("horses")
+      end
+    end
+
     def teardown
       if ActiveRecord::Base.connection.table_exists?("horses")
         ActiveRecord::Base.connection.drop_table("horses")
@@ -53,5 +66,16 @@ module ActiveRecord
       migration.migrate :down
       assert !migration.connection.table_exists?("horses")
     end
+
+    def test_legacy_up
+      LegacyMigration.migrate :up
+      assert ActiveRecord::Base.connection.table_exists?("horses"), "horses should exist"
+    end
+
+    def test_legacy_down
+      LegacyMigration.migrate :up
+      LegacyMigration.migrate :down
+      assert !ActiveRecord::Base.connection.table_exists?("horses"), "horses should not exist"
+    end
   end
 end