Add support for running Rake task in a clean environment

Author: JonRowe

Changelog.md

@@ -11,6 +11,8 @@ Enhancements:
   outside of examples. (@obromios, #2601)
 * Add a minimalist quick fix style formatter, only outputs failures as
   `file:line:message`. (Romain Tartière, #2614)
+* Add support for running the Rake task in a clean environment.
+  (Jon Rowe, #2632)
 
 Bug Fixes:
 

lib/rspec/core/rake_task.rb

@@ -45,6 +45,9 @@ class RakeTask < ::Rake::TaskLib
       # A message to print to stderr when there are failures.
       attr_accessor :failure_message
 
+      # Run RSpec with a clean (empty) environment.
+      attr_accessor :with_clean_environment
+
       # Use verbose output. If this is set to true, the task will print the
       # executed spec command to stdout. Defaults to `true`.
       attr_accessor :verbose
@@ -76,7 +79,12 @@ def run_task(verbose)
         command = spec_command
         puts command if verbose
 
-        return if system(command)
+        if with_clean_environment
+          return if system({}, command, :unsetenv_others => true)
+        else
+          return if system(command)
+        end
+
         puts failure_message if failure_message
 
         return unless fail_on_error

spec/rspec/core/rake_task_spec.rb

@@ -148,6 +148,20 @@ def silence_output(&block)
       end
     end
 
+    context "with_clean_environment is set" do
+      it "removes the environment variables" do
+        with_env_vars 'MY_ENV' => 'ABC' do
+          expect {
+            task.with_clean_environment = true
+            task.ruby_opts = '-e "puts \"Environment: #{ENV.keys}\""'
+            task.run_task false
+          }.to avoid_outputting.to_stderr.and output(
+            /\["PWD"(?:, "SHLVL")?(?:, "_")?(?:, "__CF_USER_TEXT_ENCODING")?\]/
+          ).to_stdout_from_any_process
+        end
+      end
+    end
+
     def loaded_files
       args = Shellwords.split(spec_command)
       args -= [task.class::RUBY, "-S", task.rspec_path]