Add an utils.Unreachable exception

16 files changed, 37 insertions, 24 deletions

diff --git a/.coveragerc b/.coveragerc
index 18fb85ba4..9ba8e8a5e 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -12,6 +12,7 @@ exclude_lines =
     def __repr__
     raise AssertionError
     raise NotImplementedError
+    raise utils\.Unreachable
     if __name__ == ["']__main__["']:
 
 [xml]
diff --git a/qutebrowser/browser/browsertab.py b/qutebrowser/browser/browsertab.py
index 57a3f6ba7..eb0e55c4b 100644
--- a/qutebrowser/browser/browsertab.py
+++ b/qutebrowser/browser/browsertab.py
@@ -706,8 +706,8 @@ class AbstractTab(QWidget):
         # This only gives us some mild protection against re-using events, but
         # it's certainly better than a segfault.
         if getattr(evt, 'posted', False):
-            raise AssertionError("Can't re-use an event which was already "
-                                 "posted!")
+            raise utils.Unreachable("Can't re-use an event which was already "
+                                    "posted!")
         recipient = self.event_target()
         evt.posted = True
         QApplication.postEvent(recipient, evt)
diff --git a/qutebrowser/browser/shared.py b/qutebrowser/browser/shared.py
index ab1b6ad9f..b6bfefe7b 100644
--- a/qutebrowser/browser/shared.py
+++ b/qutebrowser/browser/shared.py
@@ -22,7 +22,7 @@
 import html
 
 from qutebrowser.config import config
-from qutebrowser.utils import usertypes, message, log, objreg, jinja
+from qutebrowser.utils import usertypes, message, log, objreg, jinja, utils
 from qutebrowser.mainwindow import mainwindow
 
 
@@ -182,7 +182,7 @@ def ignore_certificate_errors(url, errors, abort_on):
         return False
     else:
         raise ValueError("Invalid ssl_strict value {!r}".format(ssl_strict))
-    raise AssertionError("Not reached")
+    raise utils.Unreachable
 
 
 def feature_permission(url, option, msg, yes_action, no_action, abort_on):
diff --git a/qutebrowser/completion/completer.py b/qutebrowser/completion/completer.py
index 6eb8b51c4..2e5b75f2d 100644
--- a/qutebrowser/completion/completer.py
+++ b/qutebrowser/completion/completer.py
@@ -153,8 +153,7 @@ class Completer(QObject):
                     "partitioned: {} '{}' {}".format(prefix, center, postfix))
                 return prefix, center, postfix
 
-        # We should always return above
-        assert False, parts
+        raise utils.Unreachable("Not all parts consumed: {}".format(parts))
 
     @pyqtSlot(str)
     def on_selection_changed(self, text):
diff --git a/qutebrowser/completion/completionwidget.py b/qutebrowser/completion/completionwidget.py
index f1be785e1..29f4f6653 100644
--- a/qutebrowser/completion/completionwidget.py
+++ b/qutebrowser/completion/completionwidget.py
@@ -180,6 +180,7 @@ class CompletionView(QTreeView):
                 return self.model().last_item()
             else:
                 return self.model().first_item()
+
         while True:
             idx = self.indexAbove(idx) if upwards else self.indexBelow(idx)
             # wrap around if we arrived at beginning/end
@@ -193,6 +194,8 @@ class CompletionView(QTreeView):
                 # Item is a real item, not a category header -> success
                 return idx
 
+        raise utils.Unreachable
+
     def _next_category_idx(self, upwards):
         """Get the index of the previous/next category.
 
@@ -222,6 +225,8 @@ class CompletionView(QTreeView):
                 self.scrollTo(idx)
                 return idx.child(0, 0)
 
+        raise utils.Unreachable
+
     @cmdutils.register(instance='completion',
                        modes=[usertypes.KeyMode.command], scope='window')
     @cmdutils.argument('which', choices=['next', 'prev', 'next-category',
diff --git a/qutebrowser/config/configdata.py b/qutebrowser/config/configdata.py
index 143cbd49a..b265ab8fc 100644
--- a/qutebrowser/config/configdata.py
+++ b/qutebrowser/config/configdata.py
@@ -174,6 +174,7 @@ def _parse_yaml_backends(name, node):
     elif isinstance(node, dict):
         return _parse_yaml_backends_dict(name, node)
     _raise_invalid_node(name, 'backends', node)
+    raise utils.Unreachable
 
 
 def _read_yaml(yaml_data):
diff --git a/qutebrowser/keyinput/basekeyparser.py b/qutebrowser/keyinput/basekeyparser.py
index 658b52d2d..b435ac52c 100644
--- a/qutebrowser/keyinput/basekeyparser.py
+++ b/qutebrowser/keyinput/basekeyparser.py
@@ -214,7 +214,7 @@ class BaseKeyParser(QObject):
         elif match == self.Match.other:
             pass
         else:
-            raise AssertionError("Invalid match value {!r}".format(match))
+            raise utils.Unreachable("Invalid match value {!r}".format(match))
         return match
 
     def _match_key(self, cmd_input):
diff --git a/qutebrowser/mainwindow/statusbar/command.py b/qutebrowser/mainwindow/statusbar/command.py
index 3e0a339a3..ab8ac7b5d 100644
--- a/qutebrowser/mainwindow/statusbar/command.py
+++ b/qutebrowser/mainwindow/statusbar/command.py
@@ -26,7 +26,7 @@ from qutebrowser.keyinput import modeman, modeparsers
 from qutebrowser.commands import cmdexc, cmdutils
 from qutebrowser.misc import cmdhistory, editor
 from qutebrowser.misc import miscwidgets as misc
-from qutebrowser.utils import usertypes, log, objreg, message
+from qutebrowser.utils import usertypes, log, objreg, message, utils
 from qutebrowser.config import config
 
 
@@ -221,8 +221,8 @@ class Command(misc.MinimalLineEditMixin, misc.CommandLineEdit):
         elif text[0] in modeparsers.STARTCHARS:
             super().set_prompt(text[0])
         else:
-            raise AssertionError("setText got called with invalid text "
-                                 "'{}'!".format(text))
+            raise utils.Unreachable("setText got called with invalid text "
+                                    "'{}'!".format(text))
         super().setText(text)
 
     def keyPressEvent(self, e):
diff --git a/qutebrowser/misc/backendproblem.py b/qutebrowser/misc/backendproblem.py
index 8a51d50ce..8cc5b71b2 100644
--- a/qutebrowser/misc/backendproblem.py
+++ b/qutebrowser/misc/backendproblem.py
@@ -152,7 +152,7 @@ def _show_dialog(*args, **kwargs):
     elif status == _Result.restart:
         quitter.restart()
     else:
-        assert False, status
+        raise utils.Unreachable(status)
 
     sys.exit(usertypes.Exit.err_init)
 
@@ -199,8 +199,7 @@ def _handle_nouveau_graphics():
         buttons=[button],
     )
 
-    # Should never be reached
-    assert False
+    raise utils.Unreachable
 
 
 def _handle_wayland():
@@ -239,8 +238,7 @@ def _handle_wayland():
                  "(based on Chromium). "
         )
 
-    # Should never be reached
-    assert False
+    raise utils.Unreachable
 
 
 @attr.s
@@ -359,8 +357,7 @@ def _check_backend_modules():
                 html.escape(imports.webengine_error))
         )
 
-    # Should never be reached
-    assert False
+    raise utils.Unreachable
 
 
 def init():
diff --git a/qutebrowser/misc/miscwidgets.py b/qutebrowser/misc/miscwidgets.py
index f398feb4c..5d3e9b5ca 100644
--- a/qutebrowser/misc/miscwidgets.py
+++ b/qutebrowser/misc/miscwidgets.py
@@ -241,7 +241,7 @@ class WrapperLayout(QLayout):
         self._widget = None
 
     def addItem(self, _widget):
-        raise AssertionError("Should never be called!")
+        raise utils.Unreachable
 
     def sizeHint(self):
         return self._widget.sizeHint()
@@ -250,7 +250,7 @@ class WrapperLayout(QLayout):
         return None
 
     def takeAt(self, _index):
-        raise AssertionError("Should never be called!")
+        raise utils.Unreachable
 
     def setGeometry(self, rect):
         self._widget.setGeometry(rect)
diff --git a/qutebrowser/misc/split.py b/qutebrowser/misc/split.py
index bdde2b7ee..2ae8b3792 100644
--- a/qutebrowser/misc/split.py
+++ b/qutebrowser/misc/split.py
@@ -21,7 +21,7 @@
 
 import re
 
-from qutebrowser.utils import log
+from qutebrowser.utils import log, utils
 
 
 class ShellLexer:
@@ -117,7 +117,8 @@ class ShellLexer:
                 else:
                     self.token += nextchar
             else:
-                raise AssertionError("Invalid state {!r}!".format(self.state))
+                raise utils.Unreachable(
+                    "Invalid state {!r}!".format(self.state))
         if self.state in self.escape and not self.keep:
             self.token += self.state
         if self.token or self.quoted:
diff --git a/qutebrowser/utils/utils.py b/qutebrowser/utils/utils.py
index 8333c4132..b277ccb77 100644
--- a/qutebrowser/utils/utils.py
+++ b/qutebrowser/utils/utils.py
@@ -60,6 +60,11 @@ is_windows = sys.platform.startswith('win')
 is_posix = os.name == 'posix'
 
 
+class Unreachable(Exception):
+
+    """Raised when there was unreachable code."""
+
+
 class ClipboardError(Exception):
 
     """Raised if the clipboard contents are unavailable for some reason."""
diff --git a/tests/end2end/fixtures/testprocess.py b/tests/end2end/fixtures/testprocess.py
index 7836ab79a..ac220af58 100644
--- a/tests/end2end/fixtures/testprocess.py
+++ b/tests/end2end/fixtures/testprocess.py
@@ -404,6 +404,8 @@ class Process(QObject):
                     self._log("----> found it")
                 return match
 
+        raise quteutils.Unreachable
+
     def _wait_for_match(self, spy, kwargs):
         """Try matching the kwargs with the given QSignalSpy."""
         for args in spy:
diff --git a/tests/unit/browser/test_tab.py b/tests/unit/browser/test_tab.py
index a2a34d9ce..d67ee4c8f 100644
--- a/tests/unit/browser/test_tab.py
+++ b/tests/unit/browser/test_tab.py
@@ -20,6 +20,7 @@
 import pytest
 
 from qutebrowser.browser import browsertab
+from qutebrowser.utils import utils
 
 pytestmark = pytest.mark.usefixtures('redirect_webengine_data')
 
@@ -54,7 +55,7 @@ def tab(request, qtbot, tab_registry, cookiejar_and_cache, mode_manager):
             'qutebrowser.browser.webengine.webenginetab')
         tab_class = webenginetab.WebEngineTab
     else:
-        assert False
+        raise utils.Unreachable
 
     t = tab_class(win_id=0, mode_manager=mode_manager)
     qtbot.add_widget(t)
@@ -67,7 +68,7 @@ class Zoom(browsertab.AbstractZoom):
         pass
 
     def factor(self):
-        assert False
+        raise utils.Unreachable
 
 
 class Tab(browsertab.AbstractTab):
diff --git a/tests/unit/commands/test_userscripts.py b/tests/unit/commands/test_userscripts.py
index 32f9a1bb9..3b6a69710 100644
--- a/tests/unit/commands/test_userscripts.py
+++ b/tests/unit/commands/test_userscripts.py
@@ -64,6 +64,7 @@ def runner(request, runtime_tmpdir):
     if (not utils.is_posix and
             request.param is userscripts._POSIXUserscriptRunner):
         pytest.skip("Requires a POSIX os")
+        raise utils.Unreachable
     else:
         return request.param()
 
diff --git a/tests/unit/utils/test_version.py b/tests/unit/utils/test_version.py
index 3d01fcfb5..620e0688a 100644
--- a/tests/unit/utils/test_version.py
+++ b/tests/unit/utils/test_version.py
@@ -795,7 +795,7 @@ class FakeQSslSocket:
     def sslLibraryVersionString(self):
         """Fake for QSslSocket::sslLibraryVersionString()."""
         if self._version is None:
-            raise AssertionError("Got called with version None!")
+            raise utils.Unreachable("Got called with version None!")
         return self._version