add a more restricted codepath for templates fixes #13390

railties/lib/rails/generators/app_base.rb

@@ -14,6 +14,7 @@ module Rails
       DATABASES.concat(JDBC_DATABASES)
 
       attr_accessor :rails_template
+      attr_accessor :app_template
       add_shebang_option!
 
       argument :app_path, type: :string
@@ -26,6 +27,9 @@ module Rails
         class_option :template,           type: :string, aliases: '-m',
                                           desc: "Path to some #{name} template (can be a filesystem path or URL)"
 
+        class_option :app_template,       type: :string, aliases: '-n',
+                                          desc: "Path to some #{name} template (can be a filesystem path or URL)"
+
         class_option :skip_gemfile,       type: :boolean, default: false,
                                           desc: "Don't create a Gemfile"
 
@@ -122,6 +126,10 @@ module Rails
         }.curry[@gem_filter]
       end
 
+      def remove_gem(name)
+        add_gem_entry_filter { |gem| gem.name != name }
+      end
+
       def builder
         @builder ||= begin
           builder_class = get_builder_class
@@ -162,6 +170,10 @@ module Rails
           @target.send :add_gem_entry_filter, *args, &block
         end
 
+        def remove_gem(*args, &block)
+          @target.send :remove_gem, *args, &block
+        end
+
         def method_missing(name, *args, &block)
           @commands << [name, args, block]
         end
@@ -180,7 +192,8 @@ module Rails
       def apply_rails_template
         @recorder = TemplateRecorder.new self
 
-        apply(rails_template, target: @recorder) if rails_template
+        apply(rails_template, target: self) if rails_template
+        apply(app_template, target: @recorder) if app_template
       rescue Thor::Error, LoadError, Errno::ENOENT => e
         raise Error, "The template [#{rails_template}] could not be loaded. Error: #{e}"
       end
@@ -210,13 +223,18 @@ module Rails
 
       def set_default_accessors!
         self.destination_root = File.expand_path(app_path, destination_root)
-        self.rails_template = case options[:template]
-          when /^https?:\/\//
-            options[:template]
-          when String
-            File.expand_path(options[:template], Dir.pwd)
-          else
-            options[:template]
+        self.rails_template = expand_template options[:template]
+        self.app_template = expand_template options[:app_template]
+      end
+
+      def expand_template(name)
+        case name
+        when /^https?:\/\//
+          name
+        when String
+          File.expand_path(name, Dir.pwd)
+        else
+          name
         end
       end
 

railties/test/generators/app_generator_test.rb

@@ -163,12 +163,21 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_arbitrary_code
+    output = Tempfile.open('my_template') do |template|
+      template.puts 'puts "You are using Rails version #{Rails::VERSION::STRING}."'
+      template.close
+      run_generator([destination_root, "-m", template.path])
+    end
+    assert_match 'You are using', output
+  end
+
   def test_add_gemfile_entry
     Tempfile.open('my_template') do |template|
       template.puts 'gemfile_entry "tenderlove"'
       template.flush
       template.close
-      run_generator([destination_root, "-m", template.path])
+      run_generator([destination_root, "-n", template.path])
       assert_file "Gemfile", /tenderlove/
     end
   end
@@ -176,9 +185,21 @@ class AppGeneratorTest < Rails::Generators::TestCase
   def test_add_skip_entry
     Tempfile.open 'my_template' do |template|
       template.puts 'add_gem_entry_filter { |gem| gem.name != "jbuilder" }'
-      template.flush
+      template.close
 
-      run_generator([destination_root, "-m", template.path])
+      run_generator([destination_root, "-n", template.path])
+      assert_file "Gemfile" do |contents|
+        assert_no_match 'jbuilder', contents
+      end
+    end
+  end
+
+  def test_remove_gem
+    Tempfile.open 'my_template' do |template|
+      template.puts 'remove_gem "jbuilder"'
+      template.close
+
+      run_generator([destination_root, "-n", template.path])
       assert_file "Gemfile" do |contents|
         assert_no_match 'jbuilder', contents
       end
@@ -190,7 +211,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
       template.puts 'add_gem_entry_filter { |gem| gem.name != "turbolinks" }'
       template.flush
 
-      run_generator([destination_root, "-m", template.path])
+      run_generator([destination_root, "-n", template.path])
       assert_file "Gemfile" do |contents|
         assert_no_match 'turbolinks', contents
       end