Handle QApplication.aboutToQuit signal to fix RuntimeError "wrapped C…

…/C++ object of has been deleted"

src/tribler-gui/tribler_gui/core_manager.py

@@ -46,6 +46,13 @@ def __init__(self, root_state_dir, api_port, api_key, error_handler):
         self.last_core_stderr_output: str = ''
 
         connect(self.events_manager.tribler_started, self.on_core_connected)
+        app = QApplication.instance()
+        if app is not None:
+            # app can be None in tests where Qt application is not created
+            connect(app.aboutToQuit, self.on_about_to_quit)
+
+    def on_about_to_quit(self):
+        self.quitting_app = True
 
     def on_core_connected(self, _):
         if not self.core_finished:
@@ -101,24 +108,32 @@ def on_core_started(self):
         self.core_running = True
 
     def on_core_stdout_read_ready(self):
+        if self.quitting_app:
+            # Reading at this stage can lead to the error "wrapped C/C++ object of type QProcess has been deleted"
+            return
+
         raw_output = bytes(self.core_process.readAllStandardOutput())
         self.last_core_stdout_output = raw_output.decode("utf-8").strip()
+
         try:
             print(self.last_core_stdout_output)  # print core output # noqa: T001
         except OSError:
             # Possible reason - cannot write to stdout as it was already closed during the application shutdown
-            if not self.quitting_app:
-                raise
+            pass
 
     def on_core_stderr_read_ready(self):
+        if self.quitting_app:
+            # Reading at this stage can lead to the error "wrapped C/C++ object of type QProcess has been deleted"
+            return
+
         raw_output = bytes(self.core_process.readAllStandardError())
         self.last_core_stderr_output = raw_output.decode("utf-8").strip()
+
         try:
             print(self.last_core_stderr_output, file=sys.stderr)  # print core output # noqa: T001
         except OSError:
             # Possible reason - cannot write to stdout as it was already closed during the application shutdown
-            if not self.quitting_app:
-                raise
+            pass
 
     def stop(self, quit_app_on_core_finished=True):
         if quit_app_on_core_finished:

src/tribler-gui/tribler_gui/tests/test_core_manager.py

@@ -61,13 +61,6 @@ def test_on_core_stdout_stderr_read_ready_os_error():
     core_manager = CoreManager(MagicMock(), MagicMock(), MagicMock(), MagicMock())
     core_manager.core_process = MagicMock(read_all=MagicMock(return_value=''))
 
-    with pytest.raises(OSError):
-        core_manager.on_core_stdout_read_ready()
-
-    with pytest.raises(OSError):
-        core_manager.on_core_stderr_read_ready()
-
-    core_manager.quitting_app = True
-    # no exception during shutting down
+    # check that OSError exception is suppressed when writing to stdout and stderr
     core_manager.on_core_stdout_read_ready()
     core_manager.on_core_stderr_read_ready()