1 files changed, 35 insertions, 5 deletions
diff --git a/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb b/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
index 1509e34473..a3c274d9b9 100644
--- a/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
+++ b/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
@@ -7,19 +7,49 @@ module ActiveRecord
 
       def create_migration_file
         set_local_assigns!
+        validate_file_name!
         migration_template "migration.rb", "db/migrate/#{file_name}.rb"
       end
 
       protected
-        attr_reader :migration_action
+      attr_reader :migration_action, :join_tables
 
-        def set_local_assigns!
-          if file_name =~ /^(add|remove)_.*_(?:to|from)_(.*)/
-            @migration_action = $1
-            @table_name       = $2.pluralize
+      def set_local_assigns!
+        case file_name
+        when /^(add|remove)_.*_(?:to|from)_(.*)/
+          @migration_action = $1
+          @table_name       = $2.pluralize
+        when /join_table/
+          if attributes.length == 2
+            @migration_action = 'join'
+            @join_tables      = attributes.map(&:plural_name)
+
+            set_index_names
           end
         end
+      end
+
+      def set_index_names
+        attributes.each_with_index do |attr, i|
+          attr.index_name = [attr, attributes[i - 1]].map{ |a| index_name_for(a) }
+        end
+      end
 
+      def index_name_for(attribute)
+        if attribute.foreign_key?
+          attribute.name
+        else
+          attribute.name.singularize.foreign_key
+        end.to_sym
+      end
+      
+      private
+
+        def validate_file_name!
+          unless file_name =~ /^[_a-z0-9]+$/
+            raise IllegalMigrationNameError.new(file_name)
+          end
+        end
     end
   end
 end