From 5d0d51b6badb1ce5d23bb4a2b9c2d7d9e7104e54 Mon Sep 17 00:00:00 2001
From: Sam Stephenson <sam@37signals.com>
Date: Sun, 6 Feb 2011 21:50:03 -0600
Subject: [PATCH] therubyracer gem installs an incompatible `v8` binary - make
 sure we don't use it

---
 lib/execjs/external_runtime.rb | 13 +++++++++++--
 lib/execjs/runtimes.rb         |  2 ++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/lib/execjs/external_runtime.rb b/lib/execjs/external_runtime.rb
index 50515ac..04ba042 100644
--- a/lib/execjs/external_runtime.rb
+++ b/lib/execjs/external_runtime.rb
@@ -6,6 +6,8 @@ module ExecJS
     def initialize(options)
       @command     = options[:command]
       @runner_path = options[:runner_path]
+      @test_args   = options[:test_args]
+      @test_match  = options[:test_match]
     end
 
     def eval(source)
@@ -22,8 +24,15 @@ module ExecJS
 
     def available?
       command = @command.split(/\s+/).first
-      `which #{command}`
-      $? == 0
+      binary = `which #{command}`
+      if $? == 0
+        if @test_args
+          output = "#{binary} #{@test_args} 2>&1"
+          output.match(@test_match)
+        else
+          true
+        end
+      end
     end
 
     protected
diff --git a/lib/execjs/runtimes.rb b/lib/execjs/runtimes.rb
index dae435c..b68cf2d 100644
--- a/lib/execjs/runtimes.rb
+++ b/lib/execjs/runtimes.rb
@@ -20,6 +20,8 @@ module ExecJS
 
     define_runtime :V8,
       :command => "v8",
+      :test_args => "--help",
+      :test_match => /--crankshaft/,
       :runner_path => runner_path("basic.js")
 
     define_runtime :Node,