Rails migrations which automatically put the new filename in your paste buffer

migration.rb

# this monkey-patches code defined in railties-3.1.0.rc1/lib/rails/generators/migration.rb
# (obviously, this might differ very slightly in the latest release candidate)

module Rails
  module Generators
    module Migration
      module ClassMethods
      # differs from the "real" version by only one line
      def migration_template(source, destination=nil, config={})
        destination = File.expand_path(destination || source, self.destination_root)

        migration_dir = File.dirname(destination)
        @migration_number     = self.class.next_migration_number(migration_dir)
        @migration_file_name  = File.basename(destination).sub(/\.rb$/, '')
        @migration_class_name = @migration_file_name.camelize

        destination = self.class.migration_exists?(migration_dir, @migration_file_name)

        if !(destination && options[:skip]) && behavior == :invoke
          if destination && options.force?
            remove_file(destination)
          elsif destination
            raise Error, "Another migration is already named #{@migration_file_name}: #{destination}"
          end
          destination = File.join(migration_dir, "#{@migration_number}_#{@migration_file_name}.rb")

          system("printf #{destination} | pbcopy") # this is that one line
        end

        template(source, destination, config)
      end
    end
  end
end

# note that if you change the line above, reversing the order of migration_number and
# migration_file_name, you can also get migration filenames which are not, from the perspective
# of experienced Unix users, completely fucking insane in their incomprehensible disregard
# for the incredible usefulness of tab completion (a baffling flaw also shared by Rails's
# config.ru default rackup file name).

# HOWEVER, making that change very likely breaks rake db:migrate, so I'm not going to advocate that
# unless I find time to make sure it works. :-)

yeah, it needs some actual tests at this point, but first I just want to be able to install it and get the base use case happening.

I didn't get this part:

You can get around that by using method added. While it generated the file correctly, when I ran the migrations, it did not run.

does that mean you got around it with method added, or you just tried? curious.

Actually, it looks like in Rails 3.1, the original file loads, then the init.rb loads and the monkeypatch happens as expected.

However, I was using Rails 3.0.7 which seems to load in the reverse order, so I had to use the self.method_added so I could redefine the method after the original was loaded. I think I have all the working parts for 3.0.7 and 3.1 (no tests, but the base case of swapping the name/version) but its all junk right now and I'm working to clean it up, then fork your project and send a pull request.

If you want to wait for tomorrow or Saturday, I can do that. If you'd rather hack on it now, here's the other monkey patches that I found to be needed:

module Rails
  module Generators
    module Migration
      module ClassMethods
        def migration_exists?(dirname, file_name) #:nodoc:
          migration_lookup_at(dirname).grep(/#{file_name}_\d+.rb$/).first
        end
        def migration_lookup_at(dirname) #:nodoc:
           Dir.glob("#{dirname}/*_[0-9]*.rb")
        end

(then back out of the ends) ....

Your migration_template method needed to swap the name and number.

module ActiveRecord
  class Migrator
    def migrations
      @migrations ||= begin
        files = Dir["#{@migrations_path}/*_[0-9]*.rb"] #swapped order of search pattern

        migrations = files.inject([]) do |klasses, file|
          name, version = file.scan(/([_a-z0-9]*)_([0-9]+).rb/).first #swapped order of search pattern

          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 }
        down? ? migrations.reverse : migrations
      end
    end

... and back out of the ends.

I think that's it.

I'll take a look tomorrow. It looks pretty straight forward but I'm pretty tired.

Forked (the project, not the gist =)) and sent you a pull request. Let me know what you think, how it can be improved, etc.

merged. before I forget: I think the method_added comment got copy/pasted to a file which doesn't actually use method_added. I'll take that out later tonight or on the weekend, and then see if I have any other tweaks.

Oops. Yeah, I just figured since the other places needed it, it'd be needed there. In fact it's not, so nice catch.