Always try to keep original GEM_PATH

This fixes a problem which occures when you want to run `bundle` command
inside code that already loads `Gemfile`. When you start a command with
`bundle exec` it sets `RUBYOPT` to
`-I$PATH_TO_BUNDLER -r"bundler/setup"`. Because of that, when you run
the actual command it already requires bundler, which is fine, but since
`GEM_PATH` was cleared on the first run `ORIGINAL_ENV` will include
empty `GEM_PATH`. Now when you run `Bundler.with_clean_env`, you will
not have any bundler specific env variables, but you will also not have
original gem path, which will make it impossible to run any gem.

To fix this I try to always keep a reference to original gem path, so
it's not emptied along the way.

3 files changed, 24 insertions, 0 deletions

diff --git a/lib/bundler.rb b/lib/bundler.rb
index 8c325dac93..833b110c29 100644
--- a/lib/bundler.rb
+++ b/lib/bundler.rb
@@ -1,12 +1,14 @@
 require 'rbconfig'
 require 'fileutils'
 require 'pathname'
+require 'bundler/gem_path_manipulation'
 require 'bundler/psyched_yaml'
 require 'bundler/rubygems_ext'
 require 'bundler/rubygems_integration'
 require 'bundler/version'
 
 module Bundler
+  preserve_gem_path
   ORIGINAL_ENV = ENV.to_hash
 
   autoload :Definition,            'bundler/definition'
diff --git a/lib/bundler/gem_path_manipulation.rb b/lib/bundler/gem_path_manipulation.rb
new file mode 100644
index 0000000000..628d954c35
--- /dev/null
+++ b/lib/bundler/gem_path_manipulation.rb
@@ -0,0 +1,8 @@
+module Bundler
+  def self.preserve_gem_path
+    original_gem_path = ENV["_ORIGINAL_GEM_PATH"]
+    gem_path          = ENV["GEM_PATH"]
+    ENV["_ORIGINAL_GEM_PATH"] = gem_path          if original_gem_path.nil? || original_gem_path == ""
+    ENV["GEM_PATH"]           = original_gem_path if gem_path.nil? || gem_path == ""
+  end
+end
diff --git a/spec/runtime/with_clean_env_spec.rb b/spec/runtime/with_clean_env_spec.rb
index d317ad5eaf..c325fe85dc 100644
--- a/spec/runtime/with_clean_env_spec.rb
+++ b/spec/runtime/with_clean_env_spec.rb
@@ -25,6 +25,20 @@ describe "Bundler.with_env helpers" do
 
     it_should_behave_like "Bundler.with_*_env"
 
+    it "should keep the original GEM_PATH even in sub processes" do
+      gemfile ""
+      bundle "install --path vendor/bundle"
+
+      gem_path = ENV['GEM_PATH']
+
+      code = "Bundler.with_clean_env do;" +
+             "  print ENV['GEM_PATH'] != '';" +
+             "end"
+
+      result = bundle "exec ruby -e #{code.inspect}"
+      result.should == "true"
+    end
+
     it "should not pass any bundler environment variables" do
       Bundler.with_clean_env do
         `echo $BUNDLE_PATH`.strip.should_not == './Gemfile'