Fix rails new and rails app:update hanging on master bug.

[rodrigovilina]

Summary

Filter PATH environment variable so script doesn't loop on itself.

Fixes: #38666
Related: #39619

When updating a rails application to the master branch, and running rails app:update, if you have bin in your PATH you would get thrown into an infinite loop.

This excludes bin from the PATH variable, so when bin/yarn is called, it does not loop on itself when calling exec "yarn".

Related Issue: #38666
Also briefly mentioned here: #39282 (comment)

Other Information

[rafaelfranca]

Can we do #39619 (comment)?

[rodrigovilina]

Actually, I tried and thought it didn't work, but on second try I got it; commiting changes.

[rodrigovilina]

@rafaelfranca Done 👌 .

[rodrigovilina]

Actually, I kept testing and I don't think it's working. If the first params to exec is both the path and the command (as in
"exec PATH='#{filtered_path}' yarn"), it thinks that that's the whole command and can't find it.

Isn't it an acceptable solution to assign the full path back once the call has been finished? I reckon that having the path that we are excluding (./bin) is neither required nor suggested to run rails, hence, it is not going to happen that that path is required afterwards.

[rafaelfranca]

This is more what we had in mind:

require 'pathname'

APP_ROOT = File.expand_path('..', __dir__)
Dir.chdir(APP_ROOT) do
  executable_path = ENV["PATH"].split(File::PATH_SEPARATOR).find do |path|
    normalized_path = File.expand_path(path)

    normalized_path != __dir__ && File.executable?(Pathname.new(normalized_path).join('yarn'))
  end

  exec File.expand_path(Pathname.new(executable_path).join('yarn')), *ARGV
rescue Errno::ENOENT
  $stderr.puts "Yarn executable was not detected in the system."
  $stderr.puts "Download Yarn at https://yarnpkg.com/en/docs/install"
  exit 1
end

Can you apply those changes?

[rodrigovilina]

I'll test locally and apply 👌

[rodrigovilina]

@rafaelfranca done 👌.

[schneems]

Thank you for your work here!