Display error message when config validation failed

qutebrowser/app.py

@@ -44,7 +44,7 @@ else:
 import qutebrowser.utils.harfbuzz as harfbuzz
 harfbuzz.fix()
 
-from PyQt5.QtWidgets import QApplication, QDialog
+from PyQt5.QtWidgets import QApplication, QDialog, QMessageBox
 from PyQt5.QtCore import pyqtSlot, QTimer, QEventLoop
 
 import qutebrowser
@@ -61,6 +61,7 @@ from qutebrowser.browser.hints import HintKeyParser
 from qutebrowser.utils.appdirs import AppDirs
 from qutebrowser.utils.misc import dotted_getattr
 from qutebrowser.utils.debug import set_trace  # pylint: disable=unused-import
+from qutebrowser.config.conftypes import ValidationError
 
 
 class QuteBrowser(QApplication):
@@ -105,7 +106,17 @@ class QuteBrowser(QApplication):
             confdir = None
         else:
             confdir = self._args.confdir
-        config.init(confdir)
+        try:
+            config.init(confdir)
+        except ValidationError as e:
+            msgbox = QMessageBox(
+                QMessageBox.Critical,
+                "Error while reading config!",
+                "Error while reading config:\n\n{} -> {}:\n{}".format(
+                    e.section, e.option, e))
+            msgbox.exec_()
+            # We didn't really initialize much so far, so we just quit hard.
+            sys.exit(1)
         self.config = config.instance
         websettings.init()
 

qutebrowser/config/config.py

@@ -205,7 +205,12 @@ class Config(QObject):
             if secname not in cp:
                 continue
             for k, v in cp[secname].items():
-                self.set('conf', secname, k, v)
+                try:
+                    self.set('conf', secname, k, v)
+                except ValidationError as e:
+                    e.section = secname
+                    e.option = k
+                    raise
 
     def has_option(self, section, option):
         """Check if option exists in section.

qutebrowser/config/conftypes.py

@@ -22,7 +22,16 @@ from PyQt5.QtGui import QColor
 
 class ValidationError(ValueError):
 
-    """Exception raised when a value for a config type was invalid."""
+    """Exception raised when a value for a config type was invalid.
+
+    Class attributes:
+        section: Section in which the error occured (added when catching and
+                 re-raising the exception).
+        option: Option in which the error occured.
+    """
+
+    section = None
+    option = None
 
     def __init__(self, value, msg):
         super().__init__('Invalid value "{}" - {}'.format(value, msg))