Mysterious Rails Error: Missing Helper File

I encountered the error “Missing helper file helpers” in Rails. Here’s a memo of how I dealt with it.

Example of the error:

Rails 5 Missing helper file helpers/c:/pg/rails/tool/app/helpers/application_helper.rb_helper.rb

To explain the sequence of events, Rails suddenly started throwing an error. Suddenly. When accessing localhost, it throws an error.

After searching around, it seems that changing the app’s folder name could solve it. However, it’s not simple. When I try to change the folder name, I get an access denied error, so permission changes seem necessary. I tried running a command to change folder permissions in administrator PowerShell and tried again, but for some reason it didn’t work.

I tried restarting Windows. Didn’t work.

After restarting, I was able to change the file. After stopping the Ruby process that was somehow opening the file with the handle command, I was able to rename it. Although I could rename it, it still didn’t fix the issue.

In the end, I couldn’t fix it, so I decided to use Docker. However, I also got stuck with Docker, so I decided to use VirtualBox.

Although the setup was a bit troublesome, I was able to develop to a satisfactory level.

<> By the way, this bug is still being discussed as an unresolved issue on GitHub. I can’t provide a fundamental solution here, but as a second-best option for now, try deleting the above files first, and if you still can’t solve it like me, try recreating the environment with VirtualBox or a Linux machine. </>