1 files changed, 69 insertions, 0 deletions
diff --git a/lib/bundler/environment_preserver.rb b/lib/bundler/environment_preserver.rb
new file mode 100644
index 0000000000..bf9478a299
--- /dev/null
+++ b/lib/bundler/environment_preserver.rb
@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+module Bundler
+  class EnvironmentPreserver
+    INTENTIONALLY_NIL = "BUNDLER_ENVIRONMENT_PRESERVER_INTENTIONALLY_NIL"
+    BUNDLER_KEYS = %w[
+      BUNDLE_BIN_PATH
+      BUNDLE_GEMFILE
+      BUNDLE_LOCKFILE
+      BUNDLER_VERSION
+      BUNDLER_SETUP
+      GEM_HOME
+      GEM_PATH
+      MANPATH
+      PATH
+      RB_USER_INSTALL
+      RUBYLIB
+      RUBYOPT
+    ].map(&:freeze).freeze
+    BUNDLER_PREFIX = "BUNDLER_ORIG_"
+
+    def self.from_env
+      new(ENV.to_hash, BUNDLER_KEYS)
+    end
+
+    # @param env [Hash]
+    # @param keys [Array<String>]
+    def initialize(env, keys)
+      @original = env
+      @keys = keys
+      @prefix = BUNDLER_PREFIX
+    end
+
+    # Replaces `ENV` with the bundler environment variables backed up
+    def replace_with_backup
+      ENV.replace(backup)
+    end
+
+    # @return [Hash]
+    def backup
+      env = @original.clone
+      @keys.each do |key|
+        value = env[key]
+        if !value.nil?
+          env[@prefix + key] ||= value
+        else
+          env[@prefix + key] ||= INTENTIONALLY_NIL
+        end
+      end
+      env
+    end
+
+    # @return [Hash]
+    def restore
+      env = @original.clone
+      @keys.each do |key|
+        value_original = env[@prefix + key]
+        next if value_original.nil?
+        if value_original == INTENTIONALLY_NIL
+          env.delete(key)
+        else
+          env[key] = value_original
+        end
+        env.delete(@prefix + key)
+      end
+      env
+    end
+  end
+end