Keep protocol correct on a fork after a subprocess. Fixes #264

src/debugpy/_vendored/pydevd/_pydev_bundle/pydev_monkey.py

@@ -8,6 +8,7 @@ from _pydevd_bundle.pydevd_constants import get_global_debugger, IS_WINDOWS, IS_
 from _pydev_bundle import pydev_log
 from contextlib import contextmanager
 from _pydevd_bundle import pydevd_constants
+from _pydevd_bundle.pydevd_defaults import PydevdCustomization
 
 try:
     xrange
@@ -676,9 +677,12 @@ def create_fork(original_name):
             frame = frame.f_back
         frame = None  # Just make sure we don't hold on to it.
 
+        protocol = pydevd_constants.get_protocol()
+
         child_process = getattr(os, original_name)()  # fork
         if not child_process:
             if is_new_python_process:
+                PydevdCustomization.DEFAULT_PROTOCOL = protocol
                 _on_forked_process(setup_tracing=apply_arg_patch and not is_subprocess_fork)
         else:
             if is_new_python_process:

src/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_net_command.py

@@ -129,7 +129,7 @@ class NetCommand(_BaseNetCommand):
 
             cls._showing_debug_info += 1
             try:
-                out_message = 'sending cmd --> '
+                out_message = 'sending cmd (%s) --> ' % (get_protocol(),)
                 out_message += "%20s" % ID_TO_MEANING.get(str(cmd_id), 'UNKNOWN')
                 out_message += ' '
                 out_message += text.replace('\n', ' ')

src/debugpy/_vendored/pydevd/tests_python/resources/_debugger_case_subprocess_and_fork.py

@@ -0,0 +1,28 @@
+import os
+import sys
+import subprocess
+
+
+def breaknow():
+    print('break here')
+
+
+if '--fork-in-subprocess' in sys.argv:
+    if sys.platform == 'win32':
+        popen = subprocess.Popen([sys.executable, __file__, '--forked'])
+        pid = popen.pid
+    else:
+        pid = os.fork()
+    print('currently in pid: %s, ppid: %s' % (os.getpid(), os.getppid()))
+    print('os.fork returned', pid)
+    breaknow()
+
+elif '--forked' in sys.argv:
+    print('currently in pid: %s, ppid: %s' % (os.getpid(), os.getppid()))
+    breaknow()
+
+elif '--fork-in-subprocess' not in sys.argv:
+    out = subprocess.check_output([sys.executable, __file__, '--fork-in-subprocess'])
+    breaknow()
+    print('\n\nin pid %s, output from subprocess.run:\n%s' % (os.getpid(), out.decode('utf-8')))
+    print('TEST SUCEEDED!')

src/debugpy/_vendored/pydevd/tests_python/test_debugger_json.py

@@ -4047,6 +4047,80 @@ def test_subprocess_pydevd_customization(case_setup_remote, command_line_args):
         writer.finished_ok = True
 
 
+@pytest.mark.skipif(IS_PY26, reason='Only Python 2.7 onwards.')
+def test_subprocess_then_fork(case_setup_multiprocessing):
+    import threading
+    from tests_python.debugger_unittest import AbstractWriterThread
+
+    with case_setup_multiprocessing.test_file('_debugger_case_subprocess_and_fork.py') as writer:
+        json_facade = JsonFacade(writer)
+        json_facade.write_launch(justMyCode=False)
+
+        break_line = writer.get_line_index_with_content('break here')
+        json_facade.write_set_breakpoints([break_line])
+
+        server_socket = writer.server_socket
+
+        class SecondaryProcessWriterThread(AbstractWriterThread):
+
+            TEST_FILE = writer.get_main_filename()
+            _sequence = -1
+
+        class SecondaryProcessThreadCommunication(threading.Thread):
+
+            def run(self):
+                from tests_python.debugger_unittest import ReaderThread
+
+                # Note that we accept 2 connections and then we proceed to receive the breakpoints.
+                json_facades = []
+                for i in range(2):
+                    server_socket.listen(1)
+                    self.server_socket = server_socket
+                    writer.log.append('  *** Multiprocess %s waiting on server_socket.accept()' % (i,))
+                    new_sock, addr = server_socket.accept()
+                    writer.log.append('  *** Multiprocess %s completed server_socket.accept()' % (i,))
+
+                    reader_thread = ReaderThread(new_sock)
+                    reader_thread.name = '  *** Multiprocess %s Reader Thread' % i
+                    reader_thread.start()
+                    writer.log.append('  *** Multiprocess %s started ReaderThread' % (i,))
+
+                    writer2 = SecondaryProcessWriterThread()
+                    writer2._WRITE_LOG_PREFIX = '  *** Multiprocess %s write: ' % i
+                    writer2.reader_thread = reader_thread
+                    writer2.sock = new_sock
+                    json_facade2 = JsonFacade(writer2, send_json_startup_messages=False)
+                    json_facade2.writer.write_multi_threads_single_notification(True)
+                    writer.log.append('  *** Multiprocess %s write attachThread' % (i,))
+                    json_facade2.write_attach(justMyCode=False)
+
+                    writer.log.append('  *** Multiprocess %s write set breakpoints' % (i,))
+                    json_facade2.write_set_breakpoints([break_line])
+                    writer.log.append('  *** Multiprocess %s write make initial run' % (i,))
+                    json_facade2.write_make_initial_run()
+                    json_facades.append(json_facade2)
+
+                for i, json_facade3 in enumerate(json_facades):
+                    writer.log.append('  *** Multiprocess %s wait for thread stopped' % (i,))
+                    json_facade3.wait_for_thread_stopped(line=break_line)
+                    writer.log.append('  *** Multiprocess %s continue' % (i,))
+                    json_facade3.write_continue()
+
+        secondary_process_thread_communication = SecondaryProcessThreadCommunication()
+        secondary_process_thread_communication.start()
+        time.sleep(.1)
+        json_facade.write_make_initial_run()
+
+        secondary_process_thread_communication.join(20)
+        if secondary_process_thread_communication.is_alive():
+            raise AssertionError('The SecondaryProcessThreadCommunication did not finish')
+
+        json_facade.wait_for_thread_stopped(line=break_line)
+        json_facade.write_continue()
+
+        writer.finished_ok = True
+
+
 @pytest.mark.parametrize('apply_multiprocessing_patch', [True, False])
 def test_no_subprocess_patching(case_setup_multiprocessing, apply_multiprocessing_patch):
     import threading