ipc: Handle None-socket in slots correctly.

qutebrowser/misc/ipc.py

@@ -141,8 +141,8 @@ class IPCServer(QObject):
     def on_error(self, err):
         """Convenience method which calls _socket_error on an error."""
         if self._socket is None:
-            # Sometimes this gets called from stale sockets, especially in
-            # tests.
+            log.ipc.warn("In on_error with None socket!")
+            # Sometimes this gets called from stale sockets.
             return
         self._timer.stop()
         log.ipc.debug("Socket error {}: {}".format(
@@ -185,7 +185,9 @@ class IPCServer(QObject):
         """Clean up socket when the client disconnected."""
         log.ipc.debug("Client disconnected.")
         self._timer.stop()
-        if self._socket is not None:
+        if self._socket is None:
+            log.ipc.warn("In on_disconnected with None socket!")
+        else:
             self._socket.deleteLater()
             self._socket = None
         # Maybe another connection is waiting.
@@ -194,7 +196,7 @@ class IPCServer(QObject):
     @pyqtSlot()
     def on_ready_read(self):
         """Read json data from the client."""
-        if self._socket is None:  # pragma: no cover
+        if self._socket is None:
             # This happens when doing a connection while another one is already
             # active for some reason.
             log.ipc.warn("In on_ready_read with None socket!")

tests/unit/misc/test_ipc.py

@@ -368,3 +368,21 @@ def test_timeout(qtbot, caplog, qlocalsocket, ipc_server):
             pass
 
     assert caplog.records()[-1].message == "IPC connection timed out."
+
+
+@pytest.mark.parametrize('method, args', [
+    ('on_error', [0]),
+    ('on_disconnected', []),
+    ('on_ready_read', []),
+])
+def test_ipcserver_socket_none(ipc_server, caplog, method, args):
+    func = getattr(ipc_server, method)
+    assert ipc_server._socket is None
+
+    with caplog.atLevel(logging.WARNING):
+        func(*args)
+
+    records = caplog.records()
+    assert len(records) == 1
+    msg = "In {} with None socket!".format(method)
+    assert records[0].message == msg