Use EventLoop which raises an Exception on double exec_()

qutebrowser/utils/misc.py

@@ -32,7 +32,7 @@ from urllib.parse import urljoin, urlencode
 from functools import reduce
 from distutils.version import StrictVersion as Version
 
-from PyQt5.QtCore import QCoreApplication, QStandardPaths, qVersion
+from PyQt5.QtCore import QCoreApplication, QStandardPaths, QEventLoop, qVersion
 from PyQt5.QtGui import QColor
 from pkg_resources import resource_string
 
@@ -384,3 +384,21 @@ def format_size(size, base=1024, suffix=''):
             return '{:.02f}{}{}'.format(size, p, suffix)
         size /= base
     return '{:.02f}{}{}'.format(size, prefixes[-1], suffix)
+
+
+class EventLoop(QEventLoop):
+
+    """A thin wrapper around QEventLoop which raises an exception when doing
+    exec_() multiple times.
+    """
+
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self._executing = False
+
+    def exec_(self, flags=QEventLoop.AllEvents):
+        if self._executing:
+            raise AssertionError("Eventloop is already running!")
+        self._executing = True
+        super().exec_(flags)
+        self._executing = False

qutebrowser/widgets/statusbar/prompt.py

@@ -17,7 +17,7 @@
 
 """Prompt shown in the statusbar."""
 
-from PyQt5.QtCore import pyqtSignal, pyqtSlot, QEventLoop
+from PyQt5.QtCore import pyqtSignal, pyqtSlot
 from PyQt5.QtWidgets import QHBoxLayout, QWidget, QLineEdit
 
 import qutebrowser.keyinput.modeman as modeman
@@ -25,6 +25,7 @@ import qutebrowser.commands.utils as cmdutils
 from qutebrowser.widgets.statusbar.textbase import TextBase
 from qutebrowser.widgets.misc import MinimalLineEdit
 from qutebrowser.utils.usertypes import PromptMode, Question
+from qutebrowser.utils.misc import EventLoop
 
 
 class Prompt(QWidget):
@@ -33,7 +34,7 @@ class Prompt(QWidget):
 
     Attributes:
         question: A Question object with the question to be asked to the user.
-        loop: A local QEventLoop to spin in exec_.
+        loop: A local EventLoop to spin in exec_.
         _hbox: The QHBoxLayout used to display the text and prompt.
         _txt: The TextBase instance (QLabel) used to display the prompt text.
         _input: The MinimalLineEdit instance (QLineEdit) used for the input.
@@ -50,7 +51,7 @@ class Prompt(QWidget):
         super().__init__(parent)
 
         self.question = None
-        self.loop = QEventLoop()
+        self.loop = EventLoop()
 
         self._hbox = QHBoxLayout(self)
         self._hbox.setContentsMargins(0, 0, 0, 0)