Generate `cable.js` file if does not exist when generating channel

- Before this, while generating a channel, we were not creating
  `cable.js` if it does not already exist.
- We have similar code for application mailer here -
  https://github.com/rails/rails/commit/0b3ae023d27197417541932632055cd6be4810c4.
- Based on the comment -
  https://github.com/rails/rails/issues/24418#issuecomment-205421995.

1 files changed, 8 insertions, 0 deletions

diff --git a/railties/test/generators/channel_generator_test.rb b/railties/test/generators/channel_generator_test.rb
index cda9e8b910..23d0c7b4a4 100644
--- a/railties/test/generators/channel_generator_test.rb
+++ b/railties/test/generators/channel_generator_test.rb
@@ -38,4 +38,12 @@ class ChannelGeneratorTest < Rails::Generators::TestCase
 
     assert_no_file "app/assets/javascripts/channels/chat.coffee"
   end
+
+  def test_cable_js_is_created_if_not_present_already
+    run_generator ['chat']
+    FileUtils.rm("#{destination_root}/app/assets/javascripts/cable.js")
+    run_generator ['camp']
+
+    assert_file "app/assets/javascripts/cable.js"
+  end
 end