bpo-36888: Add multiprocessing.parent_process() (GH-13247)

Lib/test/_test_multiprocessing.py

@@ -269,6 +269,64 @@ class _TestProcess(BaseTestCase):
             q.put(bytes(current.authkey))
             q.put(current.pid)
 
+    def test_parent_process_attributes(self):
+        if self.TYPE == "threads":
+            self.skipTest('test not appropriate for {}'.format(self.TYPE))
+
+        self.assertIsNone(self.parent_process())
+
+        rconn, wconn = self.Pipe(duplex=False)
+        p = self.Process(target=self._test_send_parent_process, args=(wconn,))
+        p.start()
+        p.join()
+        parent_pid, parent_name = rconn.recv()
+        self.assertEqual(parent_pid, self.current_process().pid)
+        self.assertEqual(parent_pid, os.getpid())
+        self.assertEqual(parent_name, self.current_process().name)
+
+    @classmethod
+    def _test_send_parent_process(cls, wconn):
+        from multiprocessing.process import parent_process
+        wconn.send([parent_process().pid, parent_process().name])
+
+    def test_parent_process(self):
+        if self.TYPE == "threads":
+            self.skipTest('test not appropriate for {}'.format(self.TYPE))
+
+        # Launch a child process. Make it launch a grandchild process. Kill the
+        # child process and make sure that the grandchild notices the death of
+        # its parent (a.k.a the child process).
+        rconn, wconn = self.Pipe(duplex=False)
+        p = self.Process(
+            target=self._test_create_grandchild_process, args=(wconn, ))
+        p.start()
+
+        if not rconn.poll(timeout=5):
+            raise AssertionError("Could not communicate with child process")
+        parent_process_status = rconn.recv()
+        self.assertEqual(parent_process_status, "alive")
+
+        p.terminate()
+        p.join()
+
+        if not rconn.poll(timeout=5):
+            raise AssertionError("Could not communicate with child process")
+        parent_process_status = rconn.recv()
+        self.assertEqual(parent_process_status, "not alive")
+
+    @classmethod
+    def _test_create_grandchild_process(cls, wconn):
+        p = cls.Process(target=cls._test_report_parent_status, args=(wconn, ))
+        p.start()
+        time.sleep(100)
+
+    @classmethod
+    def _test_report_parent_status(cls, wconn):
+        from multiprocessing.process import parent_process
+        wconn.send("alive" if parent_process().is_alive() else "not alive")
+        parent_process().join(timeout=5)
+        wconn.send("alive" if parent_process().is_alive() else "not alive")
+
     def test_process(self):
         q = self.Queue(1)
         e = self.Event()
@@ -5398,6 +5456,7 @@ class ProcessesMixin(BaseMixin):
     Process = multiprocessing.Process
     connection = multiprocessing.connection
     current_process = staticmethod(multiprocessing.current_process)
+    parent_process = staticmethod(multiprocessing.parent_process)
     active_children = staticmethod(multiprocessing.active_children)
     Pool = staticmethod(multiprocessing.Pool)
     Pipe = staticmethod(multiprocessing.Pipe)