Search $PATH for a binary rather than shelling out to which

[tenderlove]

I'm trying to speed up startup time for rake environment (on rails). Creating subshells came up on my list, so I'm trying to eliminate them.

This patch changes Bundler to search the PATH environment variable rather than shelling out to which. The function isn't 100% perfect as it doesn't handle "./sudo" the same way the shell does, but our input for this function is known so I don't think it matters.

[sferik]

Looks good. Thanks for your continued work on Rails performance improvements.

[wycats]

@tenderlove - just curious... did you benchmark the difference (i.e. is the newer code actually faster than shelling out)?

[sferik]

@fxn addressed your nitpick in 26fa77a.

[fxn]

@sferik that was fast :).

[tenderlove]

@wycats

require 'rubygems'
require 'benchmark/ips'

def sand_which cmd
  `which #{cmd}`
end

def blair_which cmd
  if File.executable? cmd
    cmd
  else
    path = ENV['PATH'].split(File::PATH_SEPARATOR).find { |path|
      File.executable? File.join(path, cmd)
    }
    path && File.expand_path(cmd, path)
  end
end

Benchmark.ips do |x|
  x.report("sand") { sand_which 'sudo' }
  x.report("blair") { blair_which 'sudo' }
end

[aaron@higgins git]$ ruby lol.rb 
                sand      251.0 (±4.8%) i/s -       1265 in   5.051489s (cycle=23)
               blair     3222.0 (±8.2%) i/s -      16218 in   5.076616s (cycle=306)
[aaron@higgins git]$

It's over 10x faster. Probably because the one that shells out has to shell out.

[sleeper]

That's a pitty: I proposed the same change on 2011-11-03 (#1516)... Today, nobody even had a look at it :(
Happy to see it merged by another channel, but kind of puzzled with the way mine has been handled ... Definitively not a way to encourage people to participate.