Add which support for Windows

lib/execjs.rb

@@ -1,3 +1,5 @@
+require "rbconfig"
+
 module ExecJS
   class Error < ::StandardError; end
   class RuntimeError    < Error; end
@@ -23,4 +25,8 @@ module ExecJS
   def self.root
     @root ||= File.expand_path("../execjs", __FILE__)
   end
+
+  def self.windows?
+    @windows ||= RbConfig::CONFIG["host_os"] =~ /mswin|mingw/
+  end
 end

lib/execjs/external_runtime.rb

@@ -29,8 +29,7 @@ module ExecJS
 
     protected
       def locate_binary
-        @command = @command.join(" ") if @command.is_a?(Array)
-        if binary = `which #{@command}`.split("\n").first
+        if binary = which(@command)
           if @test_args
             output = `#{binary} #{@test_args} 2>&1`
             binary if output.match(@test_match)
@@ -40,6 +39,17 @@ module ExecJS
         end
       end
 
+      def which(command)
+        Array(command).find do |name|
+          result = if ExecJS.windows?
+            `#{ExecJS.root}/support/which.bat #{name}`
+          else
+            `which #{name} 2>&1`
+          end
+          result.strip.split("\n").first
+        end
+      end
+
       def compile(source)
         runner_source.sub('#{source}', source)
       end

lib/execjs/support/which.bat

@@ -0,0 +1,2 @@
+@rem Taken from http://blogs.msdn.com/b/oldnewthing/archive/2005/01/20/357225.aspx
+@for %%e in (%PATHEXT%) do @for %%i in (%1%%e) do @if NOT "%%~$PATH:i"=="" @echo %%~$PATH:i