config/spring.rb loaded after Spring.application_root_path is memoized

[petekinnecom]

Hi,

We have run into an issue with our usage of Spring (I believe it is the same issue that folks are running in to here: https://github.com/rails/spring/issues/323). In our case, we have engines inside of an application but we only use a single top-level Gemfile. This has exposed an issue with the order of events when loading of the config/spring.rb.

For us, our config/spring.rb loaded after Spring.application_root_path is memoized and so our config/spring.rb does not have the correct effect.

Here is the issue as I have been able to track it down:

Consider running the command:

bundle exec spring rails runner 'puts :ok'

Spring loads the client/ files and decides it needs to start a server. That eventually leads to spring/commands getting loaded, which loads the config/spring.rb: https://github.com/rails/spring/blob/1f44a267a2476658af86b0bc1afb94588a36ed04/lib/spring/commands.rb#L48

Spring then decides to spawn a server in the background:

https://github.com/rails/spring/blob/1f44a267a2476658af86b0bc1afb94588a36ed04/lib/spring/application_manager.rb#L96

This process spawns and loads this file (note it is in a new process, so it will again need to read the config/spring.rb):

https://github.com/rails/spring/blob/1f44a267a2476658af86b0bc1afb94588a36ed04/lib/spring/application/boot.rb

The app.run on line 19 will lead to the server getting loaded and leads to the spring/commands.rb getting loaded which loads the config/spring.rb See: https://github.com/rails/spring/blob/1f44a267a2476658af86b0bc1afb94588a36ed04/lib/spring/application/boot.rb#L19

BUT, here is the problem, line 15: https://github.com/rails/spring/blob/1f44a267a2476658af86b0bc1afb94588a36ed04/lib/spring/application/boot.rb#L15

This calls app.app_name which traces all the way down to the line:

https://github.com/rails/spring/blob/1f44a267a2476658af86b0bc1afb94588a36ed04/lib/spring/configuration.rb#L24

This method then hits the default behavior BEFORE Spring has loaded the config/spring.rb. This value is memoized, by the time the config/spring.rb is loaded, its changes to Spring.application_root have no effect.

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So, requiring spring/commands somewhere before hitting this line solves the issue: https://github.com/rails/spring/blob/1f44a267a2476658af86b0bc1afb94588a36ed04/lib/spring/application/boot.rb#L15

However, based on this line, it seems that we want that to be lazily required, so I'm not sure where exactly the best place to put it would be: https://github.com/rails/spring/blob/1f44a267a2476658af86b0bc1afb94588a36ed04/lib/spring/application.rb#L86

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For those looking for a workaround in the meantime, adding the following to config/spring.rb will fix the issue and make Spring respect your local config/spring.rb in engine dummy apps:

Spring.instance_variable_set(:@application_root_path, nil)