Save old socket for IPC

At least on Windows with Qt 5.8, we get readyRead notifications *after*
disconnect...

qutebrowser/misc/ipc.py

@@ -27,7 +27,7 @@ import getpass
 import binascii
 import hashlib
 
-from PyQt5.QtCore import pyqtSignal, pyqtSlot, QObject, Qt, QTimer
+from PyQt5.QtCore import pyqtSignal, pyqtSlot, QObject, Qt
 from PyQt5.QtNetwork import QLocalSocket, QLocalServer, QAbstractSocket
 
 import qutebrowser
@@ -182,6 +182,7 @@ class IPCServer(QObject):
         self._server.newConnection.connect(self.handle_connection)
 
         self._socket = None
+        self._old_socket = None
         self._socketopts_ok = os.name == 'nt'
         if self._socketopts_ok:  # pragma: no cover
             # If we use setSocketOptions on Unix with Qt < 5.4, we get a
@@ -278,14 +279,7 @@ class IPCServer(QObject):
         log.ipc.debug("Client disconnected from socket 0x{:x}.".format(
             id(self._socket)))
         self._timer.stop()
-        if self._socket is None:
-            log.ipc.debug("In on_disconnected with None socket!")
-        else:
-            # For some reason Qt can still get delayed canReadNotifications
-            # internally, so if we call deleteLater() right away and then call
-            # QApplication::processEvents() somewhere in the code, we can get a
-            # segfault.
-            QTimer.singleShot(500, self._socket.deleteLater)
+        self._old_socket = self._socket
         self._socket = None
         # Maybe another connection is waiting.
         self.handle_connection()
@@ -349,17 +343,23 @@ class IPCServer(QObject):
     @pyqtSlot()
     def on_ready_read(self):
         """Read json data from the client."""
-        if self._socket is None:
+        if self._socket is None:  # pragma: no cover
             # This happens when doing a connection while another one is already
             # active for some reason.
-            log.ipc.warning("In on_ready_read with None socket!")
+            if self._old_socket is None:
+                log.ipc.warning("In on_ready_read with None socket and "
+                                "old_socket!")
                 return
+            log.ipc.debug("In on_ready_read with None socket!")
+            socket = self._old_socket
+        else:
+            socket = self._socket
         self._timer.stop()
-        while self._socket is not None and self._socket.canReadLine():
-            data = bytes(self._socket.readLine())
+        while socket is not None and socket.canReadLine():
+            data = bytes(socket.readLine())
             self.got_raw.emit(data)
             log.ipc.debug("Read from socket 0x{:x}: {!r}".format(
-                id(self._socket), data))
+                id(socket), data))
             self._handle_data(data)
         self._timer.start()
 

tests/unit/misc/test_ipc.py

@@ -587,22 +587,20 @@ def test_timeout(qtbot, caplog, qlocalsocket, ipc_server):
     assert caplog.records[-1].message.startswith("IPC connection timed out")
 
 
-@pytest.mark.parametrize('method, args, is_warning', [
-    pytest.mark.posix(('on_error', [0], False)),
-    ('on_disconnected', [], False),
-    ('on_ready_read', [], True),
-])
-def test_ipcserver_socket_none(ipc_server, caplog, method, args, is_warning):
-    func = getattr(ipc_server, method)
+def test_ipcserver_socket_none_readyread(ipc_server, caplog):
     assert ipc_server._socket is None
-
-    if is_warning:
+    assert ipc_server._old_socket is None
     with caplog.at_level(logging.WARNING):
-            func(*args)
-    else:
-        func(*args)
+        ipc_server.on_ready_read()
+    msg = "In on_ready_read with None socket and old_socket!"
+    assert msg in [r.message for r in caplog.records]
 
-    msg = "In {} with None socket!".format(method)
+
+@pytest.mark.posix
+def test_ipcserver_socket_none_error(ipc_server, caplog):
+    assert ipc_server._socket is None
+    ipc_server.on_error(0)
+    msg = "In on_error with None socket!"
     assert msg in [r.message for r in caplog.records]