Rewrite Gitlab::Utils.which function

lib/gitlab/utils.rb

@@ -120,18 +120,14 @@ module Gitlab
       Random.rand(Float::MAX.to_i).to_s(36)
     end
 
-    # See: http://stackoverflow.com/questions/2108727/which-in-ruby-checking-if-program-exists-in-path-from-ruby
-    # Cross-platform way of finding an executable in the $PATH.
+    # Behaves like `which` on Linux machines: given PATH, try to resolve the given
+    # executable name to an absolute path, or return nil.
     #
     #   which('ruby') #=> /usr/bin/ruby
-    def which(cmd, env = ENV)
-      exts = env['PATHEXT'] ? env['PATHEXT'].split(';') : ['']
-
-      env['PATH'].split(File::PATH_SEPARATOR).each do |path|
-        exts.each do |ext|
-          exe = File.join(path, "#{cmd}#{ext}")
-          return exe if File.executable?(exe) && !File.directory?(exe)
-        end
+    def which(filename)
+      ENV['PATH']&.split(File::PATH_SEPARATOR)&.each do |path|
+        full_path = File.join(path, filename)
+        return full_path if File.executable?(full_path)
       end
 
       nil

spec/lib/gitlab/utils_spec.rb

@@ -249,10 +249,16 @@ RSpec.describe Gitlab::Utils do
   end
 
   describe '.which' do
-    it 'finds the full path to an executable binary' do
-      expect(File).to receive(:executable?).with('/bin/sh').and_return(true)
+    before do
+      stub_env('PATH', '/sbin:/usr/bin:/home/joe/bin')
+    end
+
+    it 'finds the full path to an executable binary in order of appearance' do
+      expect(File).to receive(:executable?).with('/sbin/tool').ordered.and_return(false)
+      expect(File).to receive(:executable?).with('/usr/bin/tool').ordered.and_return(true)
+      expect(File).not_to receive(:executable?).with('/home/joe/bin/tool')
 
-      expect(which('sh', 'PATH' => '/bin')).to eq('/bin/sh')
+      expect(which('tool')).to eq('/usr/bin/tool')
     end
   end