Fix additional type hints. (#9543)

Type hint fixes due to Twisted 21.2.0 adding type hints.

5 files changed, 12 insertions, 6 deletions

diff --git a/synapse/config/logger.py b/synapse/config/logger.py
index e56cf846f5..999aecce5c 100644
--- a/synapse/config/logger.py
+++ b/synapse/config/logger.py
@@ -21,8 +21,10 @@ import threading
 from string import Template
 
 import yaml
+from zope.interface import implementer
 
 from twisted.logger import (
+    ILogObserver,
     LogBeginner,
     STDLibLogObserver,
     eventAsText,
@@ -227,7 +229,8 @@ def _setup_stdlib_logging(config, log_config_path, logBeginner: LogBeginner) ->
 
     threadlocal = threading.local()
 
-    def _log(event):
+    @implementer(ILogObserver)
+    def _log(event: dict) -> None:
         if "log_text" in event:
             if event["log_text"].startswith("DNSDatagramProtocol starting on "):
                 return
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 7657697bfa..ffc735ba25 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -361,7 +361,7 @@ class FederationServer(FederationBase):
                             logger.error(
                                 "Failed to handle PDU %s",
                                 event_id,
-                                exc_info=(f.type, f.value, f.getTracebackObject()),
+                                exc_info=(f.type, f.value, f.getTracebackObject()),  # type: ignore
                             )
 
         await concurrently_execute(
diff --git a/synapse/handlers/pagination.py b/synapse/handlers/pagination.py
index 059064a4eb..66dc886c81 100644
--- a/synapse/handlers/pagination.py
+++ b/synapse/handlers/pagination.py
@@ -285,7 +285,7 @@ class PaginationHandler:
         except Exception:
             f = Failure()
             logger.error(
-                "[purge] failed", exc_info=(f.type, f.value, f.getTracebackObject())
+                "[purge] failed", exc_info=(f.type, f.value, f.getTracebackObject())  # type: ignore
             )
             self._purges_by_id[purge_id].status = PurgeStatus.STATUS_FAILED
         finally:
diff --git a/synapse/http/federation/well_known_resolver.py b/synapse/http/federation/well_known_resolver.py
index 4def7d7633..ecd63e6596 100644
--- a/synapse/http/federation/well_known_resolver.py
+++ b/synapse/http/federation/well_known_resolver.py
@@ -322,7 +322,8 @@ def _cache_period_from_headers(
 
 def _parse_cache_control(headers: Headers) -> Dict[bytes, Optional[bytes]]:
     cache_controls = {}
-    for hdr in headers.getRawHeaders(b"cache-control", []):
+    cache_control_headers = headers.getRawHeaders(b"cache-control") or []
+    for hdr in cache_control_headers:
         for directive in hdr.split(b","):
             splits = [x.strip() for x in directive.split(b"=", 1)]
             k = splits[0].lower()
diff --git a/synapse/logging/context.py b/synapse/logging/context.py
index 78e27bfb00..1a7ea4fa96 100644
--- a/synapse/logging/context.py
+++ b/synapse/logging/context.py
@@ -669,7 +669,7 @@ def preserve_fn(f):
     return g
 
 
-def run_in_background(f, *args, **kwargs):
+def run_in_background(f, *args, **kwargs) -> defer.Deferred:
     """Calls a function, ensuring that the current context is restored after
     return from the function, and that the sentinel context is set once the
     deferred returned by the function completes.
@@ -697,8 +697,10 @@ def run_in_background(f, *args, **kwargs):
     if isinstance(res, types.CoroutineType):
         res = defer.ensureDeferred(res)
 
+    # At this point we should have a Deferred, if not then f was a synchronous
+    # function, wrap it in a Deferred for consistency.
     if not isinstance(res, defer.Deferred):
-        return res
+        return defer.succeed(res)
 
     if res.called and not res.paused:
         # The function should have maintained the logcontext, so we can