Additional type hints for client REST servlets (part 4) (#10728)

9 files changed, 145 insertions, 100 deletions

diff --git a/changelog.d/10728.misc b/changelog.d/10728.misc
new file mode 100644
index 0000000000..39a37b90b1
--- /dev/null
+++ b/changelog.d/10728.misc
@@ -0,0 +1 @@
+Add missing type hints to REST servlets.
diff --git a/synapse/rest/client/account.py b/synapse/rest/client/account.py
index fb5ad2906e..aefaaa8ae8 100644
--- a/synapse/rest/client/account.py
+++ b/synapse/rest/client/account.py
@@ -16,9 +16,11 @@
 import logging
 import random
 from http import HTTPStatus
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Optional, Tuple
 from urllib.parse import urlparse
 
+from twisted.web.server import Request
+
 from synapse.api.constants import LoginType
 from synapse.api.errors import (
     Codes,
@@ -28,15 +30,17 @@ from synapse.api.errors import (
 )
 from synapse.config.emailconfig import ThreepidBehaviour
 from synapse.handlers.ui_auth import UIAuthSessionDataConstants
-from synapse.http.server import finish_request, respond_with_html
+from synapse.http.server import HttpServer, finish_request, respond_with_html
 from synapse.http.servlet import (
     RestServlet,
     assert_params_in_dict,
     parse_json_object_from_request,
     parse_string,
 )
+from synapse.http.site import SynapseRequest
 from synapse.metrics import threepid_send_requests
 from synapse.push.mailer import Mailer
+from synapse.types import JsonDict
 from synapse.util.msisdn import phone_number_to_msisdn
 from synapse.util.stringutils import assert_valid_client_secret, random_string
 from synapse.util.threepids import check_3pid_allowed, validate_email
@@ -68,7 +72,7 @@ class EmailPasswordRequestTokenRestServlet(RestServlet):
                 template_text=self.config.email_password_reset_template_text,
             )
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         if self.config.threepid_behaviour_email == ThreepidBehaviour.OFF:
             if self.config.local_threepid_handling_disabled_due_to_email_config:
                 logger.warning(
@@ -159,7 +163,7 @@ class EmailPasswordRequestTokenRestServlet(RestServlet):
 class PasswordRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/password$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.auth = hs.get_auth()
@@ -169,7 +173,7 @@ class PasswordRestServlet(RestServlet):
         self._set_password_handler = hs.get_set_password_handler()
 
     @interactive_auth_handler
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         body = parse_json_object_from_request(request)
 
         # we do basic sanity checks here because the auth layer will store these
@@ -190,6 +194,7 @@ class PasswordRestServlet(RestServlet):
         #
         # In the second case, we require a password to confirm their identity.
 
+        requester = None
         if self.auth.has_access_token(request):
             requester = await self.auth.get_user_by_req(request)
             try:
@@ -206,16 +211,15 @@ class PasswordRestServlet(RestServlet):
                 # If a password is available now, hash the provided password and
                 # store it for later.
                 if new_password:
-                    password_hash = await self.auth_handler.hash(new_password)
+                    new_password_hash = await self.auth_handler.hash(new_password)
                     await self.auth_handler.set_session_data(
                         e.session_id,
                         UIAuthSessionDataConstants.PASSWORD_HASH,
-                        password_hash,
+                        new_password_hash,
                     )
                 raise
             user_id = requester.user.to_string()
         else:
-            requester = None
             try:
                 result, params, session_id = await self.auth_handler.check_ui_auth(
                     [[LoginType.EMAIL_IDENTITY]],
@@ -230,11 +234,11 @@ class PasswordRestServlet(RestServlet):
                 # If a password is available now, hash the provided password and
                 # store it for later.
                 if new_password:
-                    password_hash = await self.auth_handler.hash(new_password)
+                    new_password_hash = await self.auth_handler.hash(new_password)
                     await self.auth_handler.set_session_data(
                         e.session_id,
                         UIAuthSessionDataConstants.PASSWORD_HASH,
-                        password_hash,
+                        new_password_hash,
                     )
                 raise
 
@@ -264,7 +268,7 @@ class PasswordRestServlet(RestServlet):
         # If we have a password in this request, prefer it. Otherwise, use the
         # password hash from an earlier request.
         if new_password:
-            password_hash = await self.auth_handler.hash(new_password)
+            password_hash: Optional[str] = await self.auth_handler.hash(new_password)
         elif session_id is not None:
             password_hash = await self.auth_handler.get_session_data(
                 session_id, UIAuthSessionDataConstants.PASSWORD_HASH, None
@@ -288,7 +292,7 @@ class PasswordRestServlet(RestServlet):
 class DeactivateAccountRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/deactivate$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.auth = hs.get_auth()
@@ -296,7 +300,7 @@ class DeactivateAccountRestServlet(RestServlet):
         self._deactivate_account_handler = hs.get_deactivate_account_handler()
 
     @interactive_auth_handler
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         body = parse_json_object_from_request(request)
         erase = body.get("erase", False)
         if not isinstance(erase, bool):
@@ -338,7 +342,7 @@ class DeactivateAccountRestServlet(RestServlet):
 class EmailThreepidRequestTokenRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/3pid/email/requestToken$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.config = hs.config
@@ -353,7 +357,7 @@ class EmailThreepidRequestTokenRestServlet(RestServlet):
                 template_text=self.config.email_add_threepid_template_text,
             )
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         if self.config.threepid_behaviour_email == ThreepidBehaviour.OFF:
             if self.config.local_threepid_handling_disabled_due_to_email_config:
                 logger.warning(
@@ -449,7 +453,7 @@ class MsisdnThreepidRequestTokenRestServlet(RestServlet):
         self.store = self.hs.get_datastore()
         self.identity_handler = hs.get_identity_handler()
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         body = parse_json_object_from_request(request)
         assert_params_in_dict(
             body, ["client_secret", "country", "phone_number", "send_attempt"]
@@ -525,11 +529,7 @@ class AddThreepidEmailSubmitTokenServlet(RestServlet):
         "/add_threepid/email/submit_token$", releases=(), unstable=True
     )
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.config = hs.config
         self.clock = hs.get_clock()
@@ -539,7 +539,7 @@ class AddThreepidEmailSubmitTokenServlet(RestServlet):
                 self.config.email_add_threepid_template_failure_html
             )
 
-    async def on_GET(self, request):
+    async def on_GET(self, request: Request) -> None:
         if self.config.threepid_behaviour_email == ThreepidBehaviour.OFF:
             if self.config.local_threepid_handling_disabled_due_to_email_config:
                 logger.warning(
@@ -596,18 +596,14 @@ class AddThreepidMsisdnSubmitTokenServlet(RestServlet):
         "/add_threepid/msisdn/submit_token$", releases=(), unstable=True
     )
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.config = hs.config
         self.clock = hs.get_clock()
         self.store = hs.get_datastore()
         self.identity_handler = hs.get_identity_handler()
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: Request) -> Tuple[int, JsonDict]:
         if not self.config.account_threepid_delegate_msisdn:
             raise SynapseError(
                 400,
@@ -632,7 +628,7 @@ class AddThreepidMsisdnSubmitTokenServlet(RestServlet):
 class ThreepidRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/3pid$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.identity_handler = hs.get_identity_handler()
@@ -640,14 +636,14 @@ class ThreepidRestServlet(RestServlet):
         self.auth_handler = hs.get_auth_handler()
         self.datastore = self.hs.get_datastore()
 
-    async def on_GET(self, request):
+    async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
 
         threepids = await self.datastore.user_get_threepids(requester.user.to_string())
 
         return 200, {"threepids": threepids}
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         if not self.hs.config.enable_3pid_changes:
             raise SynapseError(
                 400, "3PID changes are disabled on this server", Codes.FORBIDDEN
@@ -688,7 +684,7 @@ class ThreepidRestServlet(RestServlet):
 class ThreepidAddRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/3pid/add$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.identity_handler = hs.get_identity_handler()
@@ -696,7 +692,7 @@ class ThreepidAddRestServlet(RestServlet):
         self.auth_handler = hs.get_auth_handler()
 
     @interactive_auth_handler
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         if not self.hs.config.enable_3pid_changes:
             raise SynapseError(
                 400, "3PID changes are disabled on this server", Codes.FORBIDDEN
@@ -738,13 +734,13 @@ class ThreepidAddRestServlet(RestServlet):
 class ThreepidBindRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/3pid/bind$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.identity_handler = hs.get_identity_handler()
         self.auth = hs.get_auth()
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         body = parse_json_object_from_request(request)
 
         assert_params_in_dict(body, ["id_server", "sid", "client_secret"])
@@ -767,14 +763,14 @@ class ThreepidBindRestServlet(RestServlet):
 class ThreepidUnbindRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/3pid/unbind$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.identity_handler = hs.get_identity_handler()
         self.auth = hs.get_auth()
         self.datastore = self.hs.get_datastore()
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         """Unbind the given 3pid from a specific identity server, or identity servers that are
         known to have this 3pid bound
         """
@@ -798,13 +794,13 @@ class ThreepidUnbindRestServlet(RestServlet):
 class ThreepidDeleteRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/3pid/delete$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.auth = hs.get_auth()
         self.auth_handler = hs.get_auth_handler()
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         if not self.hs.config.enable_3pid_changes:
             raise SynapseError(
                 400, "3PID changes are disabled on this server", Codes.FORBIDDEN
@@ -835,7 +831,7 @@ class ThreepidDeleteRestServlet(RestServlet):
         return 200, {"id_server_unbind_result": id_server_unbind_result}
 
 
-def assert_valid_next_link(hs: "HomeServer", next_link: str):
+def assert_valid_next_link(hs: "HomeServer", next_link: str) -> None:
     """
     Raises a SynapseError if a given next_link value is invalid
 
@@ -877,11 +873,11 @@ def assert_valid_next_link(hs: "HomeServer", next_link: str):
 class WhoamiRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/whoami$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.auth = hs.get_auth()
 
-    async def on_GET(self, request):
+    async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
 
         response = {"user_id": requester.user.to_string()}
@@ -894,7 +890,7 @@ class WhoamiRestServlet(RestServlet):
         return 200, response
 
 
-def register_servlets(hs, http_server):
+def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     EmailPasswordRequestTokenRestServlet(hs).register(http_server)
     PasswordRestServlet(hs).register(http_server)
     DeactivateAccountRestServlet(hs).register(http_server)
diff --git a/synapse/rest/client/knock.py b/synapse/rest/client/knock.py
index 68fb08d0ba..0152a0c66a 100644
--- a/synapse/rest/client/knock.py
+++ b/synapse/rest/client/knock.py
@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-from typing import TYPE_CHECKING, Dict, List, Optional, Tuple
+from typing import TYPE_CHECKING, Awaitable, Dict, List, Optional, Tuple
 
 from twisted.web.server import Request
 
@@ -96,7 +96,9 @@ class KnockRoomAliasServlet(RestServlet):
 
         return 200, {"room_id": room_id}
 
-    def on_PUT(self, request: Request, room_identifier: str, txn_id: str):
+    def on_PUT(
+        self, request: Request, room_identifier: str, txn_id: str
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         set_tag("txn_id", txn_id)
 
         return self.txns.fetch_or_execute_request(
diff --git a/synapse/rest/client/register.py b/synapse/rest/client/register.py
index a28acd4041..8f3dd2a101 100644
--- a/synapse/rest/client/register.py
+++ b/synapse/rest/client/register.py
@@ -375,11 +375,7 @@ class RegistrationTokenValidityRestServlet(RestServlet):
         unstable=True,
     )
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.store = hs.get_datastore()
@@ -390,7 +386,7 @@ class RegistrationTokenValidityRestServlet(RestServlet):
             burst_count=hs.config.ratelimiting.rc_registration_token_validity.burst_count,
         )
 
-    async def on_GET(self, request):
+    async def on_GET(self, request: Request) -> Tuple[int, JsonDict]:
         await self.ratelimiter.ratelimit(None, (request.getClientIP(),))
 
         if not self.hs.config.enable_registration:
@@ -730,7 +726,11 @@ class RegisterRestServlet(RestServlet):
         return 200, return_dict
 
     async def _do_appservice_registration(
-        self, username, as_token, body, should_issue_refresh_token: bool = False
+        self,
+        username: str,
+        as_token: str,
+        body: JsonDict,
+        should_issue_refresh_token: bool = False,
     ) -> JsonDict:
         user_id = await self.registration_handler.appservice_register(
             username, as_token
diff --git a/synapse/rest/client/report_event.py b/synapse/rest/client/report_event.py
index 07ea39a8a3..d4a4adb50c 100644
--- a/synapse/rest/client/report_event.py
+++ b/synapse/rest/client/report_event.py
@@ -14,26 +14,35 @@
 
 import logging
 from http import HTTPStatus
+from typing import TYPE_CHECKING, Tuple
 
 from synapse.api.errors import Codes, SynapseError
+from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
+from synapse.http.site import SynapseRequest
+from synapse.types import JsonDict
 
 from ._base import client_patterns
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
 class ReportEventRestServlet(RestServlet):
     PATTERNS = client_patterns("/rooms/(?P<room_id>[^/]*)/report/(?P<event_id>[^/]*)$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.auth = hs.get_auth()
         self.clock = hs.get_clock()
         self.store = hs.get_datastore()
 
-    async def on_POST(self, request, room_id, event_id):
+    async def on_POST(
+        self, request: SynapseRequest, room_id: str, event_id: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         user_id = requester.user.to_string()
 
@@ -64,5 +73,5 @@ class ReportEventRestServlet(RestServlet):
         return 200, {}
 
 
-def register_servlets(hs, http_server):
+def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     ReportEventRestServlet(hs).register(http_server)
diff --git a/synapse/rest/client/room_batch.py b/synapse/rest/client/room_batch.py
index 3172aba605..ed96978448 100644
--- a/synapse/rest/client/room_batch.py
+++ b/synapse/rest/client/room_batch.py
@@ -14,10 +14,14 @@
 
 import logging
 import re
+from typing import TYPE_CHECKING, Awaitable, List, Tuple
+
+from twisted.web.server import Request
 
 from synapse.api.constants import EventContentFields, EventTypes
 from synapse.api.errors import AuthError, Codes, SynapseError
 from synapse.appservice import ApplicationService
+from synapse.http.server import HttpServer
 from synapse.http.servlet import (
     RestServlet,
     assert_params_in_dict,
@@ -25,10 +29,14 @@ from synapse.http.servlet import (
     parse_string,
     parse_strings_from_args,
 )
+from synapse.http.site import SynapseRequest
 from synapse.rest.client.transactions import HttpTransactionCache
-from synapse.types import Requester, UserID, create_requester
+from synapse.types import JsonDict, Requester, UserID, create_requester
 from synapse.util.stringutils import random_string
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
@@ -66,7 +74,7 @@ class RoomBatchSendEventRestServlet(RestServlet):
         ),
     )
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.store = hs.get_datastore()
@@ -76,7 +84,7 @@ class RoomBatchSendEventRestServlet(RestServlet):
         self.auth = hs.get_auth()
         self.txns = HttpTransactionCache(hs)
 
-    async def _inherit_depth_from_prev_ids(self, prev_event_ids) -> int:
+    async def _inherit_depth_from_prev_ids(self, prev_event_ids: List[str]) -> int:
         (
             most_recent_prev_event_id,
             most_recent_prev_event_depth,
@@ -118,7 +126,7 @@ class RoomBatchSendEventRestServlet(RestServlet):
 
     def _create_insertion_event_dict(
         self, sender: str, room_id: str, origin_server_ts: int
-    ):
+    ) -> JsonDict:
         """Creates an event dict for an "insertion" event with the proper fields
         and a random chunk ID.
 
@@ -128,7 +136,7 @@ class RoomBatchSendEventRestServlet(RestServlet):
             origin_server_ts: Timestamp when the event was sent
 
         Returns:
-            Tuple of event ID and stream ordering position
+            The new event dictionary to insert.
         """
 
         next_chunk_id = random_string(8)
@@ -164,7 +172,9 @@ class RoomBatchSendEventRestServlet(RestServlet):
 
         return create_requester(user_id, app_service=app_service)
 
-    async def on_POST(self, request, room_id):
+    async def on_POST(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=False)
 
         if not requester.app_service:
@@ -176,6 +186,7 @@ class RoomBatchSendEventRestServlet(RestServlet):
         body = parse_json_object_from_request(request)
         assert_params_in_dict(body, ["state_events_at_start", "events"])
 
+        assert request.args is not None
         prev_events_from_query = parse_strings_from_args(request.args, "prev_event")
         chunk_id_from_query = parse_string(request, "chunk_id")
 
@@ -425,16 +436,18 @@ class RoomBatchSendEventRestServlet(RestServlet):
             ],
         }
 
-    def on_GET(self, request, room_id):
+    def on_GET(self, request: Request, room_id: str) -> Tuple[int, str]:
         return 501, "Not implemented"
 
-    def on_PUT(self, request, room_id):
+    def on_PUT(
+        self, request: SynapseRequest, room_id: str
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         return self.txns.fetch_or_execute_request(
             request, self.on_POST, request, room_id
         )
 
 
-def register_servlets(hs, http_server):
+def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     msc2716_enabled = hs.config.experimental.msc2716_enabled
 
     if msc2716_enabled:
diff --git a/synapse/rest/client/room_keys.py b/synapse/rest/client/room_keys.py
index 263596be86..37e39570f6 100644
--- a/synapse/rest/client/room_keys.py
+++ b/synapse/rest/client/room_keys.py
@@ -13,16 +13,23 @@
 # limitations under the License.
 
 import logging
+from typing import TYPE_CHECKING, Optional, Tuple
 
 from synapse.api.errors import Codes, NotFoundError, SynapseError
+from synapse.http.server import HttpServer
 from synapse.http.servlet import (
     RestServlet,
     parse_json_object_from_request,
     parse_string,
 )
+from synapse.http.site import SynapseRequest
+from synapse.types import JsonDict
 
 from ._base import client_patterns
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
@@ -31,16 +38,14 @@ class RoomKeysServlet(RestServlet):
         "/room_keys/keys(/(?P<room_id>[^/]+))?(/(?P<session_id>[^/]+))?$"
     )
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.auth = hs.get_auth()
         self.e2e_room_keys_handler = hs.get_e2e_room_keys_handler()
 
-    async def on_PUT(self, request, room_id, session_id):
+    async def on_PUT(
+        self, request: SynapseRequest, room_id: Optional[str], session_id: Optional[str]
+    ) -> Tuple[int, JsonDict]:
         """
         Uploads one or more encrypted E2E room keys for backup purposes.
         room_id: the ID of the room the keys are for (optional)
@@ -133,7 +138,9 @@ class RoomKeysServlet(RestServlet):
         ret = await self.e2e_room_keys_handler.upload_room_keys(user_id, version, body)
         return 200, ret
 
-    async def on_GET(self, request, room_id, session_id):
+    async def on_GET(
+        self, request: SynapseRequest, room_id: Optional[str], session_id: Optional[str]
+    ) -> Tuple[int, JsonDict]:
         """
         Retrieves one or more encrypted E2E room keys for backup purposes.
         Symmetric with the PUT version of the API.
@@ -215,7 +222,9 @@ class RoomKeysServlet(RestServlet):
 
         return 200, room_keys
 
-    async def on_DELETE(self, request, room_id, session_id):
+    async def on_DELETE(
+        self, request: SynapseRequest, room_id: Optional[str], session_id: Optional[str]
+    ) -> Tuple[int, JsonDict]:
         """
         Deletes one or more encrypted E2E room keys for a user for backup purposes.
 
@@ -242,16 +251,12 @@ class RoomKeysServlet(RestServlet):
 class RoomKeysNewVersionServlet(RestServlet):
     PATTERNS = client_patterns("/room_keys/version$")
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.auth = hs.get_auth()
         self.e2e_room_keys_handler = hs.get_e2e_room_keys_handler()
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         """
         Create a new backup version for this user's room_keys with the given
         info.  The version is allocated by the server and returned to the user
@@ -295,16 +300,14 @@ class RoomKeysNewVersionServlet(RestServlet):
 class RoomKeysVersionServlet(RestServlet):
     PATTERNS = client_patterns("/room_keys/version(/(?P<version>[^/]+))?$")
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.auth = hs.get_auth()
         self.e2e_room_keys_handler = hs.get_e2e_room_keys_handler()
 
-    async def on_GET(self, request, version):
+    async def on_GET(
+        self, request: SynapseRequest, version: Optional[str]
+    ) -> Tuple[int, JsonDict]:
         """
         Retrieve the version information about a given version of the user's
         room_keys backup.  If the version part is missing, returns info about the
@@ -332,7 +335,9 @@ class RoomKeysVersionServlet(RestServlet):
                 raise SynapseError(404, "No backup found", Codes.NOT_FOUND)
         return 200, info
 
-    async def on_DELETE(self, request, version):
+    async def on_DELETE(
+        self, request: SynapseRequest, version: Optional[str]
+    ) -> Tuple[int, JsonDict]:
         """
         Delete the information about a given version of the user's
         room_keys backup.  If the version part is missing, deletes the most
@@ -351,7 +356,9 @@ class RoomKeysVersionServlet(RestServlet):
         await self.e2e_room_keys_handler.delete_version(user_id, version)
         return 200, {}
 
-    async def on_PUT(self, request, version):
+    async def on_PUT(
+        self, request: SynapseRequest, version: Optional[str]
+    ) -> Tuple[int, JsonDict]:
         """
         Update the information about a given version of the user's room_keys backup.
 
@@ -385,7 +392,7 @@ class RoomKeysVersionServlet(RestServlet):
         return 200, {}
 
 
-def register_servlets(hs, http_server):
+def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     RoomKeysServlet(hs).register(http_server)
     RoomKeysVersionServlet(hs).register(http_server)
     RoomKeysNewVersionServlet(hs).register(http_server)
diff --git a/synapse/rest/client/sendtodevice.py b/synapse/rest/client/sendtodevice.py
index d537d811d8..3322c8ef48 100644
--- a/synapse/rest/client/sendtodevice.py
+++ b/synapse/rest/client/sendtodevice.py
@@ -13,15 +13,21 @@
 # limitations under the License.
 
 import logging
-from typing import Tuple
+from typing import TYPE_CHECKING, Awaitable, Tuple
 
 from synapse.http import servlet
+from synapse.http.server import HttpServer
 from synapse.http.servlet import assert_params_in_dict, parse_json_object_from_request
+from synapse.http.site import SynapseRequest
 from synapse.logging.opentracing import set_tag, trace
 from synapse.rest.client.transactions import HttpTransactionCache
+from synapse.types import JsonDict
 
 from ._base import client_patterns
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
@@ -30,11 +36,7 @@ class SendToDeviceRestServlet(servlet.RestServlet):
         "/sendToDevice/(?P<message_type>[^/]*)/(?P<txn_id>[^/]*)$"
     )
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.auth = hs.get_auth()
@@ -42,14 +44,18 @@ class SendToDeviceRestServlet(servlet.RestServlet):
         self.device_message_handler = hs.get_device_message_handler()
 
     @trace(opname="sendToDevice")
-    def on_PUT(self, request, message_type, txn_id):
+    def on_PUT(
+        self, request: SynapseRequest, message_type: str, txn_id: str
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         set_tag("message_type", message_type)
         set_tag("txn_id", txn_id)
         return self.txns.fetch_or_execute_request(
             request, self._put, request, message_type, txn_id
         )
 
-    async def _put(self, request, message_type, txn_id):
+    async def _put(
+        self, request: SynapseRequest, message_type: str, txn_id: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
         content = parse_json_object_from_request(request)
@@ -59,9 +65,8 @@ class SendToDeviceRestServlet(servlet.RestServlet):
             requester, message_type, content["messages"]
         )
 
-        response: Tuple[int, dict] = (200, {})
-        return response
+        return 200, {}
 
 
-def register_servlets(hs, http_server):
+def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     SendToDeviceRestServlet(hs).register(http_server)
diff --git a/synapse/rest/client/sync.py b/synapse/rest/client/sync.py
index 65c37be3e9..1259058b9b 100644
--- a/synapse/rest/client/sync.py
+++ b/synapse/rest/client/sync.py
@@ -14,12 +14,24 @@
 import itertools
 import logging
 from collections import defaultdict
-from typing import TYPE_CHECKING, Any, Callable, Dict, List, Optional, Tuple, Union
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Awaitable,
+    Callable,
+    Dict,
+    Iterable,
+    List,
+    Optional,
+    Tuple,
+    Union,
+)
 
 from synapse.api.constants import Membership, PresenceState
 from synapse.api.errors import Codes, StoreError, SynapseError
 from synapse.api.filtering import DEFAULT_FILTER_COLLECTION, FilterCollection
 from synapse.api.presence import UserPresenceState
+from synapse.events import EventBase
 from synapse.events.utils import (
     format_event_for_client_v2_without_room_id,
     format_event_raw,
@@ -504,7 +516,7 @@ class SyncRestServlet(RestServlet):
             The room, encoded in our response format
         """
 
-        def serialize(events):
+        def serialize(events: Iterable[EventBase]) -> Awaitable[List[JsonDict]]:
             return self._event_serializer.serialize_events(
                 events,
                 time_now=time_now,