Explictly return which Qt gui has been enabled.

IPython/terminal/pt_inputhooks/__init__.py

@@ -1,132 +1,136 b''
 import importlib
 import os
 
 aliases = {
     'qt4': 'qt',
     'gtk2': 'gtk',
 }
 
 backends = [
     "qt",
     "qt5",
     "qt6",
     "gtk",
     "gtk2",
     "gtk3",
     "gtk4",
     "tk",
     "wx",
     "pyglet",
     "glut",
     "osx",
     "asyncio",
 ]
 
 registered = {}
 
 def register(name, inputhook):
     """Register the function *inputhook* as an event loop integration."""
     registered[name] = inputhook
 
 
 class UnknownBackend(KeyError):
     def __init__(self, name):
         self.name = name
 
     def __str__(self):
         return ("No event loop integration for {!r}. "
                 "Supported event loops are: {}").format(self.name,
                                     ', '.join(backends + sorted(registered)))
 
 
 def set_qt_api(gui):
     """Sets the `QT_API` environment variable if it isn't already set."""
 
     qt_api = os.environ.get("QT_API", None)
 
     from IPython.external.qt_loaders import (
         QT_API_PYQT,
         QT_API_PYQT5,
         QT_API_PYQT6,
         QT_API_PYSIDE,
         QT_API_PYSIDE2,
         QT_API_PYSIDE6,
         QT_API_PYQTv1,
         loaded_api,
     )
 
     loaded = loaded_api()
 
     qt_env2gui = {
         QT_API_PYSIDE: "qt4",
         QT_API_PYQTv1: "qt4",
         QT_API_PYQT: "qt4",
         QT_API_PYSIDE2: "qt5",
         QT_API_PYQT5: "qt5",
         QT_API_PYSIDE6: "qt6",
         QT_API_PYQT6: "qt6",
     }
     if loaded is not None and gui != "qt":
         if qt_env2gui[loaded] != gui:
             print(
                 f"Cannot switch Qt versions for this session; will use {qt_env2gui[loaded]}."
             )
-            return
+            return qt_env2gui[loaded]
 
     if qt_api is not None and gui != "qt":
         if qt_env2gui[qt_api] != gui:
             print(
                 f'Request for "{gui}" will be ignored because `QT_API` '
                 f'environment variable is set to "{qt_api}"'
             )
+            return qt_env2gui[qt_api]
     else:
         if gui == "qt5":
             try:
                 import PyQt5  # noqa
 
                 os.environ["QT_API"] = "pyqt5"
             except ImportError:
                 try:
                     import PySide2  # noqa
 
                     os.environ["QT_API"] = "pyside2"
                 except ImportError:
                     os.environ["QT_API"] = "pyqt5"
         elif gui == "qt6":
             try:
                 import PyQt6  # noqa
 
                 os.environ["QT_API"] = "pyqt6"
             except ImportError:
                 try:
                     import PySide6  # noqa
 
                     os.environ["QT_API"] = "pyside6"
                 except ImportError:
                     os.environ["QT_API"] = "pyqt6"
         elif gui == "qt":
             # Don't set QT_API; let IPython logic choose the version.
             if "QT_API" in os.environ.keys():
                 del os.environ["QT_API"]
         else:
             print(f'Unrecognized Qt version: {gui}. Should be "qt5", "qt6", or "qt".')
-            return
+            return None
+        # Import it now so we can figure out which version it is.
+        from IPython.external.qt_for_kernel import QT_API
+        return qt_env2gui[QT_API]
 
 
 def get_inputhook_name_and_func(gui):
     if gui in registered:
         return gui, registered[gui]
 
     if gui not in backends:
         raise UnknownBackend(gui)
 
     if gui in aliases:
         return get_inputhook_name_and_func(aliases[gui])
 
     gui_mod = gui
     if gui.startswith("qt"):
-        set_qt_api(gui)
+        gui = set_qt_api(gui)
         gui_mod = "qt"
 
     mod = importlib.import_module("IPython.terminal.pt_inputhooks." + gui_mod)
     return gui, mod.inputhook