Avoid unnecessary process in queue mode

[3v0k4]

Story

Ticket

#system executes the passed command into a subshell. It pretty much executes fork, exec, and wait.

#exec replaces the current process avoiding a fork/wait.

Also, using exec delegates the exit/error handling to the replacing process making the code introduced in https://github.com/KnapsackPro/knapsack_pro-ruby/commit/7862c5e6 unneeded:

      exitstatus = $?.exitstatus
      if exitstatus.nil?
        puts 'Something went wrong. Most likely, the process has been killed. Knapsack Pro has been terminated.'
        Kernel.exit(1)
      else
        Kernel.exit(exitstatus)
      end

Also the following form seems to work:

Kernel.exec({ "RAILS_ENV" => "test", "RACK_ENV" => "test" }, "#{$PROGRAM_NAME} 'knapsack_pro:queue:rspec_go[#{args[:rspec_args]}]'")

See the #spawn docs for more on that.

Reference:

• Definition of metacharacter
• Subshell vs subprocess
• https://github.com/KnapsackPro/knapsack_pro-ruby/pull/199

Checklist reminder

• [x] You added the changes to the UNRELEASED section of the CHANGELOG.md, including the needed bump (ie, patch, minor, major)
• [x] More testing (including bin/knapsack_pro_all)
• [x] You follow the architecture outlined below for RSpec in Queue Mode, which is a work in progress (feel free to propose changes):
  • Pure: lib/knapsack_pro/pure/queue/rspec_pure.rb contains pure functions that are unit tested.
  • Extension: lib/knapsack_pro/extensions/rspec_extension.rb encapsulates calls to RSpec internals and is integration and e2e tested.
  • Runner: lib/knapsack_pro/runners/queue/rspec_runner.rb invokes the pure code and the extension to produce side effects, which are integration and e2e tested.

Manual Tests

namespace :knapsack_pro do
  namespace :queue do
    task :rspec, [:rspec_args] do |_, args|
      Kernel.exec("RAILS_ENV=test RACK_ENV=test RAILS_X=something #{$PROGRAM_NAME} 'knapsack_pro:queue:rspec_go[#{args[:rspec_args]}]'")
      raise "err"
    end

    task :rspec_go, [:rspec_args] do |_, args|
      puts ENV.filter { |k, v| k.include?("RAILS_") }
      exit 10
    end
  end
end

$ bin/knapsack_pro_queue_rspec 1 2 20240601-01
{"RAILS_X"=>"something", "RAILS_ENV"=>"test"}

$ echo $?
10

namespace :knapsack_pro do
  namespace :queue do
    task :rspec, [:rspec_args] do |_, args|
      Kernel.exec("RAILS_ENV=test RACK_ENV=test RAILS_X=something #{$PROGRAM_NAME} 'knapsack_pro:queue:rspec_go[#{args[:rspec_args]}]'")
      raise "err"
    end

    task :rspec_go, [:rspec_args] do |_, args|
      puts ENV.filter { |k, v| k.include?("RAILS_") }
      raise StandardError
    end
  end
end

$ bin/knapsack_pro_queue_rspec 1 2 20240601-01
{"RAILS_X"=>"something", "RAILS_ENV"=>"test"}
rake aborted!
StandardError: StandardError (StandardError)
/Users/3v0k4/code/knapsack/knapsack_pro-ruby/lib/tasks/queue/rspec.rake:14:in `block (3 levels) in <top (required)>'
/Users/3v0k4/.rvm/gems/ruby-3.2.2/gems/rake-13.2.1/exe/rake:27:in `<top (required)>'
/Users/3v0k4/.rvm/gems/ruby-3.2.2/bin/ruby_executable_hooks:22:in `eval'
/Users/3v0k4/.rvm/gems/ruby-3.2.2/bin/ruby_executable_hooks:22:in `<main>'
Tasks: TOP => knapsack_pro:queue:rspec_go
(See full trace by running task with --trace)