Make it possible to use dmypy (#9692)

Running `dmypy run` will do a `mypy` check while spinning up a daemon
that makes rerunning `dmypy run` a lot faster.

`dmypy` doesn't support `follow_imports = silent` and has
`local_partial_types` enabled, so this PR enables those options and
fixes the issues that were newly raised. Note that `local_partial_types`
will be enabled by default in upcoming mypy releases.

11 files changed, 30 insertions, 6 deletions

diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index e10e33fd23..7d9930ae7b 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -558,6 +558,9 @@ class Auth:
         Returns:
             bool: False if no access_token was given, True otherwise.
         """
+        # This will always be set by the time Twisted calls us.
+        assert request.args is not None
+
         query_params = request.args.get(b"access_token")
         auth_headers = request.requestHeaders.getRawHeaders(b"Authorization")
         return bool(query_params) or bool(auth_headers)
@@ -574,6 +577,8 @@ class Auth:
             MissingClientTokenError: If there isn't a single access_token in the
                 request
         """
+        # This will always be set by the time Twisted calls us.
+        assert request.args is not None
 
         auth_headers = request.requestHeaders.getRawHeaders(b"Authorization")
         query_params = request.args.get(b"access_token")
diff --git a/synapse/config/cache.py b/synapse/config/cache.py
index 8e03f14005..4e8abbf88a 100644
--- a/synapse/config/cache.py
+++ b/synapse/config/cache.py
@@ -24,7 +24,7 @@ from ._base import Config, ConfigError
 _CACHE_PREFIX = "SYNAPSE_CACHE_FACTOR"
 
 # Map from canonicalised cache name to cache.
-_CACHES = {}
+_CACHES = {}  # type: Dict[str, Callable[[float], None]]
 
 # a lock on the contents of _CACHES
 _CACHES_LOCK = threading.Lock()
@@ -59,7 +59,9 @@ def _canonicalise_cache_name(cache_name: str) -> str:
     return cache_name.lower()
 
 
-def add_resizable_cache(cache_name: str, cache_resize_callback: Callable):
+def add_resizable_cache(
+    cache_name: str, cache_resize_callback: Callable[[float], None]
+):
     """Register a cache that's size can dynamically change
 
     Args:
diff --git a/synapse/handlers/oidc_handler.py b/synapse/handlers/oidc_handler.py
index bc3630e9e9..6624212d6f 100644
--- a/synapse/handlers/oidc_handler.py
+++ b/synapse/handlers/oidc_handler.py
@@ -149,6 +149,9 @@ class OidcHandler:
         Args:
             request: the incoming request from the browser.
         """
+        # This will always be set by the time Twisted calls us.
+        assert request.args is not None
+
         # The provider might redirect with an error.
         # In that case, just display it as-is.
         if b"error" in request.args:
diff --git a/synapse/logging/opentracing.py b/synapse/logging/opentracing.py
index 10bd4a1461..c6e6335740 100644
--- a/synapse/logging/opentracing.py
+++ b/synapse/logging/opentracing.py
@@ -262,7 +262,7 @@ logger = logging.getLogger(__name__)
 # Block everything by default
 # A regex which matches the server_names to expose traces for.
 # None means 'block everything'.
-_homeserver_whitelist = None
+_homeserver_whitelist = None  # type: Optional[re.Pattern[str]]
 
 # Util methods
 
diff --git a/synapse/replication/tcp/protocol.py b/synapse/replication/tcp/protocol.py
index 825900f64c..e829add257 100644
--- a/synapse/replication/tcp/protocol.py
+++ b/synapse/replication/tcp/protocol.py
@@ -104,7 +104,7 @@ tcp_outbound_commands_counter = Counter(
 
 # A list of all connected protocols. This allows us to send metrics about the
 # connections.
-connected_connections = []
+connected_connections = []  # type: List[BaseReplicationStreamProtocol]
 
 
 logger = logging.getLogger(__name__)
diff --git a/synapse/rest/admin/rooms.py b/synapse/rest/admin/rooms.py
index 263d8ec076..cfe1bebb91 100644
--- a/synapse/rest/admin/rooms.py
+++ b/synapse/rest/admin/rooms.py
@@ -390,6 +390,9 @@ class JoinRoomAliasServlet(ResolveRoomIdMixin, RestServlet):
     async def on_POST(
         self, request: SynapseRequest, room_identifier: str
     ) -> Tuple[int, JsonDict]:
+        # This will always be set by the time Twisted calls us.
+        assert request.args is not None
+
         requester = await self.auth.get_user_by_req(request)
         await assert_user_is_admin(self.auth, requester.user)
 
diff --git a/synapse/rest/admin/users.py b/synapse/rest/admin/users.py
index aaa56a7024..309bd2771b 100644
--- a/synapse/rest/admin/users.py
+++ b/synapse/rest/admin/users.py
@@ -833,6 +833,9 @@ class UserMediaRestServlet(RestServlet):
     async def on_GET(
         self, request: SynapseRequest, user_id: str
     ) -> Tuple[int, JsonDict]:
+        # This will always be set by the time Twisted calls us.
+        assert request.args is not None
+
         await assert_requester_is_admin(self.auth, request)
 
         if not self.is_mine(UserID.from_string(user_id)):
diff --git a/synapse/rest/client/v2_alpha/sync.py b/synapse/rest/client/v2_alpha/sync.py
index a0db0a054b..3481770c83 100644
--- a/synapse/rest/client/v2_alpha/sync.py
+++ b/synapse/rest/client/v2_alpha/sync.py
@@ -91,6 +91,9 @@ class SyncRestServlet(RestServlet):
         self._event_serializer = hs.get_event_client_serializer()
 
     async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
+        # This will always be set by the time Twisted calls us.
+        assert request.args is not None
+
         if b"from" in request.args:
             # /events used to use 'from', but /sync uses 'since'.
             # Lets be helpful and whine if we see a 'from'.
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index e590a0deab..c4ed9dfdb4 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -187,6 +187,8 @@ class PreviewUrlResource(DirectServeJsonResource):
         respond_with_json(request, 200, {}, send_cors=True)
 
     async def _async_render_GET(self, request: SynapseRequest) -> None:
+        # This will always be set by the time Twisted calls us.
+        assert request.args is not None
 
         # XXX: if get_user_by_req fails, what should we do in an async render?
         requester = await self.auth.get_user_by_req(request)
diff --git a/synapse/rest/synapse/client/pick_username.py b/synapse/rest/synapse/client/pick_username.py
index 51acaa9a92..d9ffe84489 100644
--- a/synapse/rest/synapse/client/pick_username.py
+++ b/synapse/rest/synapse/client/pick_username.py
@@ -104,6 +104,9 @@ class AccountDetailsResource(DirectServeHtmlResource):
         respond_with_html(request, 200, html)
 
     async def _async_render_POST(self, request: SynapseRequest):
+        # This will always be set by the time Twisted calls us.
+        assert request.args is not None
+
         try:
             session_id = get_username_mapping_session_cookie_from_request(request)
         except SynapseError as e:
diff --git a/synapse/util/caches/__init__.py b/synapse/util/caches/__init__.py
index f968706334..48f64eeb38 100644
--- a/synapse/util/caches/__init__.py
+++ b/synapse/util/caches/__init__.py
@@ -25,8 +25,8 @@ from synapse.config.cache import add_resizable_cache
 
 logger = logging.getLogger(__name__)
 
-caches_by_name = {}
-collectors_by_name = {}  # type: Dict
+caches_by_name = {}  # type: Dict[str, Sized]
+collectors_by_name = {}  # type: Dict[str, CacheMetric]
 
 cache_size = Gauge("synapse_util_caches_cache:size", "", ["name"])
 cache_hits = Gauge("synapse_util_caches_cache:hits", "", ["name"])