BF: clear environment variable on error

If the requested Qt version can't be loaded.

IPython/external/qt_loaders.py

@@ -1,405 +1,410 b''
 """
 This module contains factory functions that attempt
 to return Qt submodules from the various python Qt bindings.
 
 It also protects against double-importing Qt with different
 bindings, which is unstable and likely to crash
 
 This is used primarily by qt and qt_for_kernel, and shouldn't
 be accessed directly from the outside
 """
 import importlib.abc
 import sys
+import os
 import types
 from functools import partial, lru_cache
 import operator
 
 # ### Available APIs.
 # Qt6
 QT_API_PYQT6 = "pyqt6"
 QT_API_PYSIDE6 = "pyside6"
 
 # Qt5
 QT_API_PYQT5 = 'pyqt5'
 QT_API_PYSIDE2 = 'pyside2'
 
 # Qt4
 # NOTE: Here for legacy matplotlib compatibility, but not really supported on the IPython side.
 QT_API_PYQT = "pyqt"  # Force version 2
 QT_API_PYQTv1 = "pyqtv1"  # Force version 2
 QT_API_PYSIDE = "pyside"
 
 QT_API_PYQT_DEFAULT = "pyqtdefault"  # use system default for version 1 vs. 2
 
 api_to_module = {
     # Qt6
     QT_API_PYQT6: "PyQt6",
     QT_API_PYSIDE6: "PySide6",
     # Qt5
     QT_API_PYQT5: "PyQt5",
     QT_API_PYSIDE2: "PySide2",
     # Qt4
     QT_API_PYSIDE: "PySide",
     QT_API_PYQT: "PyQt4",
     QT_API_PYQTv1: "PyQt4",
     # default
     QT_API_PYQT_DEFAULT: "PyQt6",
 }
 
 
 class ImportDenier(importlib.abc.MetaPathFinder):
     """Import Hook that will guard against bad Qt imports
     once IPython commits to a specific binding
     """
 
     def __init__(self):
         self.__forbidden = set()
 
     def forbid(self, module_name):
         sys.modules.pop(module_name, None)
         self.__forbidden.add(module_name)
 
     def find_spec(self, fullname, path, target=None):
         if path:
             return
         if fullname in self.__forbidden:
             raise ImportError(
                 """
     Importing %s disabled by IPython, which has
     already imported an Incompatible QT Binding: %s
     """
                 % (fullname, loaded_api())
             )
 
 
 ID = ImportDenier()
 sys.meta_path.insert(0, ID)
 
 
 def commit_api(api):
     """Commit to a particular API, and trigger ImportErrors on subsequent
     dangerous imports"""
     modules = set(api_to_module.values())
 
     modules.remove(api_to_module[api])
     for mod in modules:
         ID.forbid(mod)
 
 
 def loaded_api():
     """Return which API is loaded, if any
 
     If this returns anything besides None,
     importing any other Qt binding is unsafe.
 
     Returns
     -------
     None, 'pyside6', 'pyqt6', 'pyside2', 'pyside', 'pyqt', 'pyqt5', 'pyqtv1'
     """
     if sys.modules.get("PyQt6.QtCore"):
         return QT_API_PYQT6
     elif sys.modules.get("PySide6.QtCore"):
         return QT_API_PYSIDE6
     elif sys.modules.get("PyQt5.QtCore"):
         return QT_API_PYQT5
     elif sys.modules.get("PySide2.QtCore"):
         return QT_API_PYSIDE2
     elif sys.modules.get("PyQt4.QtCore"):
         if qtapi_version() == 2:
             return QT_API_PYQT
         else:
             return QT_API_PYQTv1
     elif sys.modules.get("PySide.QtCore"):
         return QT_API_PYSIDE
 
     return None
 
 
 def has_binding(api):
     """Safely check for PyQt4/5, PySide or PySide2, without importing submodules
 
     Parameters
     ----------
     api : str [ 'pyqtv1' | 'pyqt' | 'pyqt5' | 'pyside' | 'pyside2' | 'pyqtdefault']
         Which module to check for
 
     Returns
     -------
     True if the relevant module appears to be importable
     """
     module_name = api_to_module[api]
     from importlib.util import find_spec
 
     required = ['QtCore', 'QtGui', 'QtSvg']
     if api in (QT_API_PYQT5, QT_API_PYSIDE2, QT_API_PYQT6, QT_API_PYSIDE6):
         # QT5 requires QtWidgets too
         required.append('QtWidgets')
 
     for submod in required:
         try:
             spec = find_spec('%s.%s' % (module_name, submod))
         except ImportError:
             # Package (e.g. PyQt5) not found
             return False
         else:
             if spec is None:
                 # Submodule (e.g. PyQt5.QtCore) not found
                 return False
 
     if api == QT_API_PYSIDE:
         # We can also safely check PySide version
         import PySide
 
         return PySide.__version_info__ >= (1, 0, 3)
 
     return True
 
 
 def qtapi_version():
     """Return which QString API has been set, if any
 
     Returns
     -------
     The QString API version (1 or 2), or None if not set
     """
     try:
         import sip
     except ImportError:
         # as of PyQt5 5.11, sip is no longer available as a top-level
         # module and needs to be imported from the PyQt5 namespace
         try:
             from PyQt5 import sip
         except ImportError:
             return
     try:
         return sip.getapi('QString')
     except ValueError:
         return
 
 
 def can_import(api):
     """Safely query whether an API is importable, without importing it"""
     if not has_binding(api):
         return False
 
     current = loaded_api()
     if api == QT_API_PYQT_DEFAULT:
         return current in [QT_API_PYQT6, None]
     else:
         return current in [api, None]
 
 
 def import_pyqt4(version=2):
     """
     Import PyQt4
 
     Parameters
     ----------
     version : 1, 2, or None
         Which QString/QVariant API to use. Set to None to use the system
         default
     ImportErrors raised within this function are non-recoverable
     """
     # The new-style string API (version=2) automatically
     # converts QStrings to Unicode Python strings. Also, automatically unpacks
     # QVariants to their underlying objects.
     import sip
 
     if version is not None:
         sip.setapi('QString', version)
         sip.setapi('QVariant', version)
 
     from PyQt4 import QtGui, QtCore, QtSvg
 
     if QtCore.PYQT_VERSION < 0x040700:
         raise ImportError("IPython requires PyQt4 >= 4.7, found %s" %
                           QtCore.PYQT_VERSION_STR)
 
     # Alias PyQt-specific functions for PySide compatibility.
     QtCore.Signal = QtCore.pyqtSignal
     QtCore.Slot = QtCore.pyqtSlot
 
     # query for the API version (in case version == None)
     version = sip.getapi('QString')
     api = QT_API_PYQTv1 if version == 1 else QT_API_PYQT
     return QtCore, QtGui, QtSvg, api
 
 
 def import_pyqt5():
     """
     Import PyQt5
 
     ImportErrors raised within this function are non-recoverable
     """
 
     from PyQt5 import QtCore, QtSvg, QtWidgets, QtGui
 
     # Alias PyQt-specific functions for PySide compatibility.
     QtCore.Signal = QtCore.pyqtSignal
     QtCore.Slot = QtCore.pyqtSlot
 
     # Join QtGui and QtWidgets for Qt4 compatibility.
     QtGuiCompat = types.ModuleType('QtGuiCompat')
     QtGuiCompat.__dict__.update(QtGui.__dict__)
     QtGuiCompat.__dict__.update(QtWidgets.__dict__)
 
     api = QT_API_PYQT5
     return QtCore, QtGuiCompat, QtSvg, api
 
 
 def import_pyqt6():
     """
     Import PyQt6
 
     ImportErrors raised within this function are non-recoverable
     """
 
     from PyQt6 import QtCore, QtSvg, QtWidgets, QtGui
 
     # Alias PyQt-specific functions for PySide compatibility.
     QtCore.Signal = QtCore.pyqtSignal
     QtCore.Slot = QtCore.pyqtSlot
 
     # Join QtGui and QtWidgets for Qt4 compatibility.
     QtGuiCompat = types.ModuleType("QtGuiCompat")
     QtGuiCompat.__dict__.update(QtGui.__dict__)
     QtGuiCompat.__dict__.update(QtWidgets.__dict__)
 
     api = QT_API_PYQT6
     return QtCore, QtGuiCompat, QtSvg, api
 
 
 def import_pyside():
     """
     Import PySide
 
     ImportErrors raised within this function are non-recoverable
     """
     from PySide import QtGui, QtCore, QtSvg
     return QtCore, QtGui, QtSvg, QT_API_PYSIDE
 
 def import_pyside2():
     """
     Import PySide2
 
     ImportErrors raised within this function are non-recoverable
     """
     from PySide2 import QtGui, QtCore, QtSvg, QtWidgets, QtPrintSupport
 
     # Join QtGui and QtWidgets for Qt4 compatibility.
     QtGuiCompat = types.ModuleType('QtGuiCompat')
     QtGuiCompat.__dict__.update(QtGui.__dict__)
     QtGuiCompat.__dict__.update(QtWidgets.__dict__)
     QtGuiCompat.__dict__.update(QtPrintSupport.__dict__)
 
     return QtCore, QtGuiCompat, QtSvg, QT_API_PYSIDE2
 
 
 def import_pyside6():
     """
     Import PySide6
 
     ImportErrors raised within this function are non-recoverable
     """
     from PySide6 import QtGui, QtCore, QtSvg, QtWidgets, QtPrintSupport
 
     # Join QtGui and QtWidgets for Qt4 compatibility.
     QtGuiCompat = types.ModuleType("QtGuiCompat")
     QtGuiCompat.__dict__.update(QtGui.__dict__)
     QtGuiCompat.__dict__.update(QtWidgets.__dict__)
     QtGuiCompat.__dict__.update(QtPrintSupport.__dict__)
 
     return QtCore, QtGuiCompat, QtSvg, QT_API_PYSIDE6
 
 
 def load_qt(api_options):
     """
     Attempt to import Qt, given a preference list
     of permissible bindings
 
     It is safe to call this function multiple times.
 
     Parameters
     ----------
     api_options : List of strings
         The order of APIs to try. Valid items are 'pyside', 'pyside2',
         'pyqt', 'pyqt5', 'pyqtv1' and 'pyqtdefault'
 
     Returns
     -------
     A tuple of QtCore, QtGui, QtSvg, QT_API
     The first three are the Qt modules. The last is the
     string indicating which module was loaded.
 
     Raises
     ------
     ImportError, if it isn't possible to import any requested
     bindings (either because they aren't installed, or because
     an incompatible library has already been installed)
     """
     loaders = {
         # Qt6
         QT_API_PYQT6: import_pyqt6,
         QT_API_PYSIDE6: import_pyside6,
         # Qt5
         QT_API_PYQT5: import_pyqt5,
         QT_API_PYSIDE2: import_pyside2,
         # Qt4
         QT_API_PYSIDE: import_pyside,
         QT_API_PYQT: import_pyqt4,
         QT_API_PYQTv1: partial(import_pyqt4, version=1),
         # default
         QT_API_PYQT_DEFAULT: import_pyqt6,
     }
 
     for api in api_options:
 
         if api not in loaders:
             raise RuntimeError(
                 "Invalid Qt API %r, valid values are: %s" %
                 (api, ", ".join(["%r" % k for k in loaders.keys()])))
 
         if not can_import(api):
             continue
 
         #cannot safely recover from an ImportError during this
         result = loaders[api]()
         api = result[-1]  # changed if api = QT_API_PYQT_DEFAULT
         commit_api(api)
         return result
     else:
+        # Clear the environment variable since it doesn't work.
+        if "QT_API" in os.environ:
+            del os.environ["QT_API"]
+
         raise ImportError(
             """
     Could not load requested Qt binding. Please ensure that
     PyQt4 >= 4.7, PyQt5, PyQt6, PySide >= 1.0.3, PySide2, or
     PySide6 is available, and only one is imported per session.
 
     Currently-imported Qt library:                              %r
     PyQt5 available (requires QtCore, QtGui, QtSvg, QtWidgets): %s
     PyQt6 available (requires QtCore, QtGui, QtSvg, QtWidgets): %s
     PySide2 installed:                                          %s
     PySide6 installed:                                          %s
     Tried to load:                                              %r
     """
             % (
                 loaded_api(),
                 has_binding(QT_API_PYQT5),
                 has_binding(QT_API_PYQT6),
                 has_binding(QT_API_PYSIDE2),
                 has_binding(QT_API_PYSIDE6),
                 api_options,
             )
         )
 
 
 def enum_factory(QT_API, QtCore):
     """Construct an enum helper to account for PyQt5 <-> PyQt6 changes."""
 
     @lru_cache(None)
     def _enum(name):
         # foo.bar.Enum.Entry (PyQt6) <=> foo.bar.Entry (non-PyQt6).
         return operator.attrgetter(
             name if QT_API == QT_API_PYQT6 else name.rpartition(".")[0]
         )(sys.modules[QtCore.__package__])
 
     return _enum