Add Bundler.with_clean_env for blocks of ruby without a bundled env

e.g. if you are in a bundled Rakefile but need to shell out to
something on your system that uses ruby like Homebrew

Fixes #225

2 files changed, 25 insertions, 0 deletions

diff --git a/lib/bundler.rb b/lib/bundler.rb
index 9d6ea3b4bd..38f28b9a63 100644
--- a/lib/bundler.rb
+++ b/lib/bundler.rb
@@ -3,8 +3,10 @@ require 'pathname'
 require 'yaml'
 require 'bundler/rubygems_ext'
 
+
 module Bundler
   VERSION = "0.9.13"
+  ORIGINAL_ENV = ENV.to_hash
 
   autoload :Definition,          'bundler/definition'
   autoload :Dependency,          'bundler/dependency'
@@ -109,6 +111,14 @@ module Bundler
       @settings ||= Settings.new(root)
     end
 
+    def with_clean_env
+      bundled_env = ENV.to_hash
+      ENV.replace(ORIGINAL_ENV)
+      yield
+    ensure
+      ENV.replace(bundled_env.to_hash)
+    end
+
   private
 
     def default_gemfile
diff --git a/spec/runtime/with_clean_env_spec.rb b/spec/runtime/with_clean_env_spec.rb
new file mode 100644
index 0000000000..3894e414a9
--- /dev/null
+++ b/spec/runtime/with_clean_env_spec.rb
@@ -0,0 +1,15 @@
+require File.expand_path('../../spec_helper', __FILE__)
+
+describe "Bundler.with_clean_env" do
+
+  it "should reset and restore the environment" do
+    gem_path = ENV['GEM_PATH']
+
+    Bundler.with_clean_env do
+      `echo $GEM_PATH`.strip.should_not == gem_path
+    end
+
+    ENV['GEM_PATH'].should == gem_path
+  end
+
+end
\ No newline at end of file