Implemented ActiveRecord::Migrations#copy based on James Adam's idea

ActiveRecord::Migration#copy allows to copy migrations from one place
to another, changing migrations versions and adding scope to filename.

For example:
ActiveRecord::Migration.copy("db/migrate",
        :blog_engine => "vendor/gems/blog/db/migrate")

will copy all migrations from vendor/gems/blog/db/migrate to db/migrate
with such format:

Versions of copied migrations will be reversioned to be appended after
migrations that already exists in db/migrate

activerecord/lib/active_record/migration.rb

@@ -383,6 +383,37 @@ def method_missing(method, *arguments, &block)
           connection.send(method, *arguments, &block)
         end
       end
+
+      def copy(destination, sources)
+        copied = []
+
+        sources.each do |scope, path|
+          destination_migrations = ActiveRecord::Migrator.migrations(destination)
+          source_migrations = ActiveRecord::Migrator.migrations(path)
+          last = destination_migrations.last
+
+          source_migrations.each do |migration|
+            next if destination_migrations.any? { |m| m.name == migration.name && m.scope == scope.to_s }
+
+            migration.version = next_migration_number(last.version + 1).to_i
+            last = migration
+
+            new_path = File.join(destination, "#{migration.version}_#{migration.name.underscore}.#{scope}.rb")
+            FileUtils.cp(migration.filename, new_path)
+            copied << new_path
+          end
+        end
+
+        copied
+      end
+
+      def next_migration_number(number)
+        if ActiveRecord::Base.timestamped_migrations
+          [Time.now.utc.strftime("%Y%m%d%H%M%S"), "%.14d" % number].max
+        else
+          "%.3d" % number
+        end
+      end
     end
   end
 
@@ -390,7 +421,7 @@ def method_missing(method, *arguments, &block)
   # until they are needed
   class MigrationProxy
 
-    attr_accessor :name, :version, :filename
+    attr_accessor :name, :version, :filename, :scope
 
     delegate :migrate, :announce, :write, :to=>:migration
 
@@ -470,6 +501,34 @@ def migrations_path
         @migrations_path ||= 'db/migrate'
       end
 
+      def migrations(path)
+        files = Dir["#{path}/[0-9]*_*.rb"]
+
+        migrations = files.inject([]) do |klasses, file|
+          version, name, scope = file.scan(/([0-9]+)_([_a-z0-9]*)\.?([_a-z0-9]*)?.rb/).first
+
+          raise IllegalMigrationNameError.new(file) unless version
+          version = version.to_i
+
+          if klasses.detect { |m| m.version == version }
+            raise DuplicateMigrationVersionError.new(version)
+          end
+
+          if klasses.detect { |m| m.name == name.camelize && m.scope == scope }
+            raise DuplicateMigrationNameError.new(name.camelize)
+          end
+
+          migration = MigrationProxy.new
+          migration.name     = name.camelize
+          migration.version  = version
+          migration.filename = file
+          migration.scope    = scope
+          klasses << migration
+        end
+
+        migrations.sort_by(&:version)
+      end
+
       private
 
       def move(direction, migrations_path, steps)
@@ -548,30 +607,7 @@ def migrate
 
     def migrations
       @migrations ||= begin
-        files = Dir["#{@migrations_path}/[0-9]*_*.rb"]
-
-        migrations = files.inject([]) do |klasses, file|
-          version, name = file.scan(/([0-9]+)_([_a-z0-9]*).rb/).first
-
-          raise IllegalMigrationNameError.new(file) unless version
-          version = version.to_i
-
-          if klasses.detect { |m| m.version == version }
-            raise DuplicateMigrationVersionError.new(version)
-          end
-
-          if klasses.detect { |m| m.name == name.camelize }
-            raise DuplicateMigrationNameError.new(name.camelize)
-          end
-
-          migration = MigrationProxy.new
-          migration.name     = name.camelize
-          migration.version  = version
-          migration.filename = file
-          klasses << migration
-        end
-
-        migrations = migrations.sort_by { |m| m.version }
+        migrations = self.class.migrations(@migrations_path)
         down? ? migrations.reverse : migrations
       end
     end

activerecord/lib/rails/generators/active_record.rb

@@ -14,6 +14,12 @@ class Base < Rails::Generators::NamedBase #:nodoc:
       def self.base_root
         File.dirname(__FILE__)
       end
+
+      # Implement the required interface for Rails::Generators::Migration.
+      def self.next_migration_number(dirname) #:nodoc:
+        next_migration_number = current_migration_number(dirname) + 1
+        ActiveRecord::Migration.next_migration_number(next_migration_number)
+      end
     end
   end
 end

activerecord/test/cases/helper.rb

@@ -83,3 +83,21 @@ def create_fixtures(*table_names, &block)
 ensure
   $stdout = original_stdout
 end
+
+class << Time
+  unless method_defined? :now_before_time_travel
+    alias_method :now_before_time_travel, :now
+  end
+
+  def now
+    (@now ||= nil) || now_before_time_travel
+  end
+
+  def travel_to(time, &block)
+    @now = time
+    block.call
+  ensure
+    @now = nil
+  end
+end
+

activerecord/test/cases/migration_test.rb

@@ -1875,5 +1875,116 @@ def with_change_table
       end
     end
   end
+
+  class CopyMigrationsTest < ActiveRecord::TestCase
+    def setup
+    end
+
+    def clear
+      ActiveRecord::Base.timestamped_migrations = true
+      to_delete = Dir[@migrations_path + "/*.rb"] - @existing_migrations
+      File.delete(*to_delete)
+    end
+
+    def test_copying_migrations_without_timestamps
+      ActiveRecord::Base.timestamped_migrations = false
+      @migrations_path = MIGRATIONS_ROOT + "/valid"
+      @existing_migrations = Dir[@migrations_path + "/*.rb"]
+
+      copied = ActiveRecord::Migration.copy(@migrations_path, {:bukkits => MIGRATIONS_ROOT + "/to_copy"})
+      assert File.exists?(@migrations_path + "/4_people_have_hobbies.bukkits.rb")
+      assert File.exists?(@migrations_path + "/5_people_have_descriptions.bukkits.rb")
+      assert_equal [@migrations_path + "/4_people_have_hobbies.bukkits.rb", @migrations_path + "/5_people_have_descriptions.bukkits.rb"], copied
+
+      files_count = Dir[@migrations_path + "/*.rb"].length
+      copied = ActiveRecord::Migration.copy(@migrations_path, {:bukkits => MIGRATIONS_ROOT + "/to_copy"})
+      assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
+      assert copied.empty?
+    ensure
+      clear
+    end
+
+    def test_copying_migrations_without_timestamps_from_2_sources
+      ActiveRecord::Base.timestamped_migrations = false
+      @migrations_path = MIGRATIONS_ROOT + "/valid"
+      @existing_migrations = Dir[@migrations_path + "/*.rb"]
+
+      sources = ActiveSupport::OrderedHash.new
+      sources[:bukkits] = sources[:omg] = MIGRATIONS_ROOT + "/to_copy"
+      ActiveRecord::Migration.copy(@migrations_path, sources)
+      assert File.exists?(@migrations_path + "/4_people_have_hobbies.omg.rb")
+      assert File.exists?(@migrations_path + "/5_people_have_descriptions.omg.rb")
+      assert File.exists?(@migrations_path + "/6_people_have_hobbies.bukkits.rb")
+      assert File.exists?(@migrations_path + "/7_people_have_descriptions.bukkits.rb")
+
+      files_count = Dir[@migrations_path + "/*.rb"].length
+      ActiveRecord::Migration.copy(@migrations_path, sources)
+      assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
+    ensure
+      clear
+    end
+
+    def test_copying_migrations_with_timestamps
+      @migrations_path = MIGRATIONS_ROOT + "/valid_with_timestamps"
+      @existing_migrations = Dir[@migrations_path + "/*.rb"]
+
+      Time.travel_to(created_at = Time.utc(2010, 7, 26, 10, 10, 10)) do
+        copied = ActiveRecord::Migration.copy(@migrations_path, {:bukkits => MIGRATIONS_ROOT + "/to_copy_with_timestamps"})
+        assert File.exists?(@migrations_path + "/20100726101010_people_have_hobbies.bukkits.rb")
+        assert File.exists?(@migrations_path + "/20100726101011_people_have_descriptions.bukkits.rb")
+        expected = [@migrations_path + "/20100726101010_people_have_hobbies.bukkits.rb",
+                    @migrations_path + "/20100726101011_people_have_descriptions.bukkits.rb"]
+        assert_equal expected, copied
+
+        files_count = Dir[@migrations_path + "/*.rb"].length
+        copied = ActiveRecord::Migration.copy(@migrations_path, {:bukkits => MIGRATIONS_ROOT + "/to_copy_with_timestamps"})
+        assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
+        assert copied.empty?
+      end
+    ensure
+      clear
+    end
+
+    def test_copying_migrations_with_timestamps_from_2_sources
+      @migrations_path = MIGRATIONS_ROOT + "/valid_with_timestamps"
+      @existing_migrations = Dir[@migrations_path + "/*.rb"]
+
+      sources = ActiveSupport::OrderedHash.new
+      sources[:bukkits] = sources[:omg] = MIGRATIONS_ROOT + "/to_copy_with_timestamps"
+
+      Time.travel_to(created_at = Time.utc(2010, 7, 26, 10, 10, 10)) do
+        copied = ActiveRecord::Migration.copy(@migrations_path, sources)
+        assert File.exists?(@migrations_path + "/20100726101010_people_have_hobbies.omg.rb")
+        assert File.exists?(@migrations_path + "/20100726101011_people_have_descriptions.omg.rb")
+        assert File.exists?(@migrations_path + "/20100726101012_people_have_hobbies.bukkits.rb")
+        assert File.exists?(@migrations_path + "/20100726101013_people_have_descriptions.bukkits.rb")
+        assert_equal 4, copied.length
+
+        files_count = Dir[@migrations_path + "/*.rb"].length
+        ActiveRecord::Migration.copy(@migrations_path, sources)
+        assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
+      end
+    ensure
+      clear
+    end
+
+    def test_copying_migrations_with_timestamps_to_destination_with_timestamps_in_future
+      @migrations_path = MIGRATIONS_ROOT + "/valid_with_timestamps"
+      @existing_migrations = Dir[@migrations_path + "/*.rb"]
+
+      Time.travel_to(created_at = Time.utc(2010, 2, 20, 10, 10, 10)) do
+        ActiveRecord::Migration.copy(@migrations_path, {:bukkits => MIGRATIONS_ROOT + "/to_copy_with_timestamps"})
+        assert File.exists?(@migrations_path + "/20100301010102_people_have_hobbies.bukkits.rb")
+        assert File.exists?(@migrations_path + "/20100301010103_people_have_descriptions.bukkits.rb")
+
+        files_count = Dir[@migrations_path + "/*.rb"].length
+        copied = ActiveRecord::Migration.copy(@migrations_path, {:bukkits => MIGRATIONS_ROOT + "/to_copy_with_timestamps"})
+        assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
+        assert copied.empty?
+      end
+    ensure
+      clear
+    end
+  end
 end
 

activerecord/test/migrations/to_copy/1_people_have_hobbies.rb

@@ -0,0 +1,9 @@
+class PeopleHaveLastNames < ActiveRecord::Migration
+  def self.up
+    add_column "people", "hobbies", :text
+  end
+
+  def self.down
+    remove_column "people", "hobbies"
+  end
+end

activerecord/test/migrations/to_copy/2_people_have_descriptions.rb

@@ -0,0 +1,9 @@
+class PeopleHaveLastNames < ActiveRecord::Migration
+  def self.up
+    add_column "people", "description", :text
+  end
+
+  def self.down
+    remove_column "people", "description"
+  end
+end

activerecord/test/migrations/to_copy_with_timestamps/20090101010101_people_have_hobbies.rb

@@ -0,0 +1,9 @@
+class PeopleHaveLastNames < ActiveRecord::Migration
+  def self.up
+    add_column "people", "hobbies", :text
+  end
+
+  def self.down
+    remove_column "people", "hobbies"
+  end
+end

activerecord/test/migrations/to_copy_with_timestamps/20090101010202_people_have_descriptions.rb

@@ -0,0 +1,9 @@
+class PeopleHaveLastNames < ActiveRecord::Migration
+  def self.up
+    add_column "people", "description", :text
+  end
+
+  def self.down
+    remove_column "people", "description"
+  end
+end

activerecord/test/migrations/valid_with_timestamps/20100101010101_people_have_last_names.rb

@@ -0,0 +1,9 @@
+class PeopleHaveLastNames < ActiveRecord::Migration
+  def self.up
+    add_column "people", "last_name", :string
+  end
+
+  def self.down
+    remove_column "people", "last_name"
+  end
+end

activerecord/test/migrations/valid_with_timestamps/20100201010101_we_need_reminders.rb

@@ -0,0 +1,12 @@
+class WeNeedReminders < ActiveRecord::Migration
+  def self.up
+    create_table("reminders") do |t|
+      t.column :content, :text
+      t.column :remind_at, :datetime
+    end
+  end
+
+  def self.down
+    drop_table "reminders"
+  end
+end

activerecord/test/migrations/valid_with_timestamps/20100301010101_innocent_jointable.rb

@@ -0,0 +1,12 @@
+class InnocentJointable < ActiveRecord::Migration
+  def self.up
+    create_table("people_reminders", :id => false) do |t|
+      t.column :reminder_id, :integer
+      t.column :person_id, :integer
+    end
+  end
+
+  def self.down
+    drop_table "people_reminders"
+  end
+end