fix double int without breaking stdin

CHANGELOG.md

@@ -8,6 +8,8 @@
 
 ### Fixed
 
+- Avoid double sending int while also not breaking debugging [#891](https://github.com/grosser/parallel_tests/pull/891)
+
 ## 4.1.0 - 2023-01-14
 
 ### Fixed

lib/parallel_tests/cli.rb

@@ -32,9 +32,23 @@ def handle_interrupt
       @graceful_shutdown_attempted ||= false
       Kernel.exit if @graceful_shutdown_attempted
 
-      # The Pid class's synchronize method can't be called directly from a trap
-      # Using Thread workaround https://github.com/ddollar/foreman/issues/332
-      Thread.new { ParallelTests.stop_all_processes }
+      # In a shell, all sub-processes also get an interrupt, so they shut themselves down.
+      # In a background process this does not happen and we need to do it ourselves.
+      # We cannot always send the interrupt since then the sub-processes would get interrupted twice when in foreground
+      # and that messes with interrupt handling.
+      #
+      # (can simulate detached with `(bundle exec parallel_rspec test/a_spec.rb -n 2 &)`)
+      # also the integration test "passes on int signal to child processes" is detached.
+      #
+      # On windows getpgid does not work so we resort to always killing which is the smaller bug.
+      #
+      # The ParallelTests::Pids `synchronize` method can't be called directly from a trap,
+      # using Thread workaround https://github.com/ddollar/foreman/issues/332
+      Thread.new do
+        if Gem.win_platform? || ((child_pid = ParallelTests.pids.all.first) && Process.getpgid(child_pid) != Process.pid)
+          ParallelTests.stop_all_processes
+        end
+      end
 
       @graceful_shutdown_attempted = true
     end

lib/parallel_tests/test/runner.rb

@@ -108,11 +108,10 @@ def print_command(command, env)
         end
 
         def execute_command_and_capture_output(env, cmd, options)
-          pid = nil
-
-          popen_options = { pgroup: true }
+          popen_options = {} # do not add `pgroup: true`, it will break `binding.irb` inside the test
           popen_options[:err] = [:child, :out] if options[:combine_stderr]
 
+          pid = nil
           output = IO.popen(env, cmd, popen_options) do |io|
             pid = io.pid
             ParallelTests.pids.add(pid)

spec/integration_spec.rb

@@ -667,7 +667,10 @@ class A < Spinach::FeatureSteps
     # Process.kill on Windows doesn't work as expected. It kills all process group instead of just one process.
     it "passes on int signal to child processes", unless: Gem.win_platform? do
       timeout = 2
-      write "spec/test_spec.rb", "sleep #{timeout}; describe { specify { 'Should not get here' }; specify { p 'Should not get here either'} }"
+      write(
+        "spec/test_spec.rb",
+        "sleep #{timeout}; describe { specify { p 'Should not get here' }; specify { p 'Should not get here either'} }"
+      )
       pid = nil
       Thread.new { sleep timeout - 0.5; Process.kill("INT", pid) }
       result = run_tests(["spec"], processes: 2, type: 'rspec', fail: true) { |io| pid = io.pid }