Backport PR #12842: Reclaim sys.excepthook for interactive shell in %gui qt

IPython/terminal/pt_inputhooks/qt.py

@@ -1,54 +1,68 b''
 import sys
 import os
 from IPython.external.qt_for_kernel import QtCore, QtGui
+from IPython import get_ipython
 
 # If we create a QApplication, keep a reference to it so that it doesn't get
 # garbage collected.
 _appref = None
 _already_warned = False
 
 
+def _reclaim_excepthook():
+    shell = get_ipython()
+    if shell is not None:
+        sys.excepthook = shell.excepthook
+
+
 def inputhook(context):
     global _appref
     app = QtCore.QCoreApplication.instance()
     if not app:
         if sys.platform == 'linux':
             if not os.environ.get('DISPLAY') \
                     and not os.environ.get('WAYLAND_DISPLAY'):
                 import warnings
                 global _already_warned
                 if not _already_warned:
                     _already_warned = True
                     warnings.warn(
                         'The DISPLAY or WAYLAND_DISPLAY environment variable is '
                         'not set or empty and Qt5 requires this environment '
                         'variable. Deactivate Qt5 code.'
                     )
                 return
         QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
         _appref = app = QtGui.QApplication([" "])
+
+        # "reclaim" IPython sys.excepthook after event loop starts
+        # without this, it defaults back to BaseIPythonApplication.excepthook
+        # and exceptions in the Qt event loop are rendered without traceback
+        # formatting and look like "bug in IPython".
+        QtCore.QTimer.singleShot(0, _reclaim_excepthook)
+
     event_loop = QtCore.QEventLoop(app)
 
     if sys.platform == 'win32':
         # The QSocketNotifier method doesn't appear to work on Windows.
         # Use polling instead.
         timer = QtCore.QTimer()
         timer.timeout.connect(event_loop.quit)
         while not context.input_is_ready():
             timer.start(50)  # 50 ms
             event_loop.exec_()
             timer.stop()
     else:
         # On POSIX platforms, we can use a file descriptor to quit the event
         # loop when there is input ready to read.
         notifier = QtCore.QSocketNotifier(context.fileno(),
                                           QtCore.QSocketNotifier.Read)
         try:
             # connect the callback we care about before we turn it on
             notifier.activated.connect(lambda: event_loop.exit())
             notifier.setEnabled(True)
             # only start the event loop we are not already flipped
             if not context.input_is_ready():
                 event_loop.exec_()
         finally:
             notifier.setEnabled(False)