Use casts for reactors (instead of ignoring or asserting).

synapse/app/_base.py

@@ -33,12 +33,13 @@ from typing import (
     List,
     NoReturn,
     Tuple,
+    cast,
 )
 
 from cryptography.utils import CryptographyDeprecationWarning
 
 import twisted
-from twisted.internet import defer, error, reactor
+from twisted.internet import defer, error, reactor as _reactor
 from twisted.internet.interfaces import IOpenSSLContextFactory, IReactorSSL, IReactorTCP
 from twisted.internet.protocol import ServerFactory
 from twisted.internet.tcp import Port
@@ -61,6 +62,7 @@ from synapse.logging.context import PreserveLoggingContext
 from synapse.metrics import register_threadpool
 from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.metrics.jemalloc import setup_jemalloc_stats
+from synapse.types import ISynapseReactor
 from synapse.util.caches.lrucache import setup_expire_lru_cache_entries
 from synapse.util.daemonize import daemonize_process
 from synapse.util.gai_resolver import GAIResolver
@@ -70,6 +72,11 @@ from synapse.util.versionstring import get_version_string
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
+# Twisted injects the global reactor to make it easier to import, this confuses
+# mypy which thinks it is a module. Tell it that it a more proper type.
+reactor = cast(ISynapseReactor, _reactor)
+
+
 logger = logging.getLogger(__name__)
 
 # list of tuples of function, args list, kwargs dict
@@ -92,8 +99,7 @@ def register_sighup(func: Callable[..., None], *args: Any, **kwargs: Any) -> Non
 def start_worker_reactor(
     appname: str,
     config: HomeServerConfig,
-    # mypy can't figure out what the default reactor is.
-    run_command: Callable[[], None] = reactor.run,  # type: ignore[attr-defined]
+    run_command: Callable[[], None] = reactor.run,
 ) -> None:
     """Run the reactor in the main process
 
@@ -128,8 +134,7 @@ def start_reactor(
     daemonize: bool,
     print_pidfile: bool,
     logger: logging.Logger,
-    # mypy can't figure out what the default reactor is.
-    run_command: Callable[[], None] = reactor.run,  # type: ignore[attr-defined]
+    run_command: Callable[[], None] = reactor.run,
 ) -> None:
     """Run the reactor in the main process
 
@@ -242,8 +247,7 @@ def register_start(cb: Callable[..., Awaitable], *args: Any, **kwargs: Any) -> N
             # on as normal.
             os._exit(1)
 
-    # mypy can't figure out what the default reactor is.
-    reactor.callWhenRunning(lambda: defer.ensureDeferred(wrapper()))  # type: ignore[attr-defined]
+    reactor.callWhenRunning(lambda: defer.ensureDeferred(wrapper()))
 
 
 def listen_metrics(bind_addresses: Iterable[str], port: int) -> None:
@@ -285,8 +289,7 @@ def listen_tcp(
     bind_addresses: Collection[str],
     port: int,
     factory: ServerFactory,
-    # mypy can't figure out what the default reactor is.
-    reactor: IReactorTCP = reactor,  # type: ignore[assignment]
+    reactor: IReactorTCP = reactor,
     backlog: int = 50,
 ) -> List[Port]:
     """
@@ -312,8 +315,7 @@ def listen_ssl(
     port: int,
     factory: ServerFactory,
     context_factory: IOpenSSLContextFactory,
-    # mypy can't figure out what the default reactor is.
-    reactor: IReactorSSL = reactor,  # type: ignore[assignment]
+    reactor: IReactorSSL = reactor,
     backlog: int = 50,
 ) -> List[Port]:
     """

synapse/logging/handlers.py

@@ -3,7 +3,7 @@ import time
 from logging import Handler, LogRecord
 from logging.handlers import MemoryHandler
 from threading import Thread
-from typing import Optional
+from typing import Optional, cast
 
 from twisted.internet.interfaces import IReactorCore
 
@@ -56,7 +56,7 @@ class PeriodicallyFlushingMemoryHandler(MemoryHandler):
         if reactor is None:
             from twisted.internet import reactor as global_reactor
 
-            reactor_to_use = global_reactor  # type: ignore[assignment]
+            reactor_to_use = cast(IReactorCore, global_reactor)
         else:
             reactor_to_use = reactor
 

synapse/util/async_helpers.py

@@ -31,13 +31,13 @@ from typing import (
     Set,
     TypeVar,
     Union,
+    cast,
 )
 
 import attr
 from typing_extensions import ContextManager
 
 from twisted.internet import defer
-from twisted.internet.base import ReactorBase
 from twisted.internet.defer import CancelledError
 from twisted.internet.interfaces import IReactorTime
 from twisted.python import failure
@@ -271,8 +271,7 @@ class Linearizer:
         if not clock:
             from twisted.internet import reactor
 
-            assert isinstance(reactor, ReactorBase)
-            clock = Clock(reactor)
+            clock = Clock(cast(IReactorTime, reactor))
         self._clock = clock
         self.max_count = max_count