Assert for valid application names. [#3556 status:resolved]

railties/lib/rails/generators/rails/app/app_generator.rb

@@ -53,8 +53,9 @@ module Rails::Generators
 
     def create_root
       self.destination_root = File.expand_path(app_path, destination_root)
-      empty_directory '.'
+      valid_app_const?
 
+      empty_directory '.'
       set_default_accessors!
       FileUtils.cd(destination_root)
     end
@@ -193,7 +194,14 @@ module Rails::Generators
       end
 
       def app_const
-        @app_const ||= "#{app_name.classify}::Application"
+        @app_const ||= "#{app_name.gsub(/\W/, '_').squeeze('_').classify}::Application"
+      end
+
+      def valid_app_const?
+        case app_const
+        when /^\d/
+          raise Error, "Invalid application name #{app_name}. Please give a name which does not start with numbers."
+        end
       end
 
       def app_secret

railties/test/generators/app_generator_test.rb

@@ -53,6 +53,16 @@ class AppGeneratorTest < GeneratorsTestCase
     assert_match /Invalid value for \-\-database option/, content
   end
 
+  def test_invalid_application_name_raises_an_error
+    content = capture(:stderr){ Rails::Generators::AppGenerator.start [File.join(destination_root, "43-things")] }
+    assert_equal "Invalid application name 43-things. Please give a name which does not start with numbers.\n", content
+  end
+
+  def test_invalid_application_name_is_fixed
+    silence(:stdout){ Rails::Generators::AppGenerator.start [File.join(destination_root, "things-43")] }
+    assert_file "things-43/config/environment.rb", /Things43::Application/
+  end
+
   def test_config_database_is_added_by_default
     run_generator
     assert_file "config/database.yml", /sqlite3/