Fix additional type hints from Twisted 21.2.0. (#9591)

synapse/logging/_remote.py

@@ -32,8 +32,9 @@ from twisted.internet.endpoints import (
     TCP4ClientEndpoint,
     TCP6ClientEndpoint,
 )
-from twisted.internet.interfaces import IPushProducer, IStreamClientEndpoint, ITransport
+from twisted.internet.interfaces import IPushProducer, IStreamClientEndpoint
 from twisted.internet.protocol import Factory, Protocol
+from twisted.internet.tcp import Connection
 from twisted.python.failure import Failure
 
 logger = logging.getLogger(__name__)
@@ -52,7 +53,9 @@ class LogProducer:
         format: A callable to format the log record to a string.
     """
 
-    transport = attr.ib(type=ITransport)
+    # This is essentially ITCPTransport, but that is missing certain fields
+    # (connected and registerProducer) which are part of the implementation.
+    transport = attr.ib(type=Connection)
     _format = attr.ib(type=Callable[[logging.LogRecord], str])
     _buffer = attr.ib(type=deque)
     _paused = attr.ib(default=False, type=bool, init=False)
@@ -149,8 +152,6 @@ class RemoteHandler(logging.Handler):
         if self._connection_waiter:
             return
 
-        self._connection_waiter = self._service.whenConnected(failAfterFailures=1)
-
         def fail(failure: Failure) -> None:
             # If the Deferred was cancelled (e.g. during shutdown) do not try to
             # reconnect (this will cause an infinite loop of errors).
@@ -163,9 +164,13 @@ class RemoteHandler(logging.Handler):
             self._connect()
 
         def writer(result: Protocol) -> None:
+            # Force recognising transport as a Connection and not the more
+            # generic ITransport.
+            transport = result.transport  # type: Connection  # type: ignore
+
             # We have a connection. If we already have a producer, and its
             # transport is the same, just trigger a resumeProducing.
-            if self._producer and result.transport is self._producer.transport:
+            if self._producer and transport is self._producer.transport:
                 self._producer.resumeProducing()
                 self._connection_waiter = None
                 return
@@ -177,14 +182,16 @@ class RemoteHandler(logging.Handler):
             # Make a new producer and start it.
             self._producer = LogProducer(
                 buffer=self._buffer,
-                transport=result.transport,
+                transport=transport,
                 format=self.format,
             )
-            result.transport.registerProducer(self._producer, True)
+            transport.registerProducer(self._producer, True)
             self._producer.resumeProducing()
             self._connection_waiter = None
 
-        self._connection_waiter.addCallbacks(writer, fail)
+        deferred = self._service.whenConnected(failAfterFailures=1)  # type: Deferred
+        deferred.addCallbacks(writer, fail)
+        self._connection_waiter = deferred
 
     def _handle_pressure(self) -> None:
         """