Enable mypy checking for unreachable code and fix instances. (#8432)

4 files changed, 10 insertions, 18 deletions

diff --git a/synapse/storage/databases/main/censor_events.py b/synapse/storage/databases/main/censor_events.py
index f211ddbaf8..4bb2b9c28c 100644
--- a/synapse/storage/databases/main/censor_events.py
+++ b/synapse/storage/databases/main/censor_events.py
@@ -21,8 +21,8 @@ from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.database import DatabasePool
 from synapse.storage.databases.main.cache import CacheInvalidationWorkerStore
-from synapse.storage.databases.main.events import encode_json
 from synapse.storage.databases.main.events_worker import EventsWorkerStore
+from synapse.util.frozenutils import frozendict_json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
@@ -105,7 +105,7 @@ class CensorEventsStore(EventsWorkerStore, CacheInvalidationWorkerStore, SQLBase
                 and original_event.internal_metadata.is_redacted()
             ):
                 # Redaction was allowed
-                pruned_json = encode_json(
+                pruned_json = frozendict_json_encoder.encode(
                     prune_event_dict(
                         original_event.room_version, original_event.get_dict()
                     )
@@ -171,7 +171,7 @@ class CensorEventsStore(EventsWorkerStore, CacheInvalidationWorkerStore, SQLBase
                 return
 
             # Prune the event's dict then convert it to JSON.
-            pruned_json = encode_json(
+            pruned_json = frozendict_json_encoder.encode(
                 prune_event_dict(event.room_version, event.get_dict())
             )
 
diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index 18def01f50..78e645592f 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -52,16 +52,6 @@ event_counter = Counter(
 )
 
 
-def encode_json(json_object):
-    """
-    Encode a Python object as JSON and return it in a Unicode string.
-    """
-    out = frozendict_json_encoder.encode(json_object)
-    if isinstance(out, bytes):
-        out = out.decode("utf8")
-    return out
-
-
 _EventCacheEntry = namedtuple("_EventCacheEntry", ("event", "redacted_event"))
 
 
@@ -743,7 +733,9 @@ class PersistEventsStore:
                     logger.exception("")
                     raise
 
-                metadata_json = encode_json(event.internal_metadata.get_dict())
+                metadata_json = frozendict_json_encoder.encode(
+                    event.internal_metadata.get_dict()
+                )
 
                 sql = "UPDATE event_json SET internal_metadata = ? WHERE event_id = ?"
                 txn.execute(sql, (metadata_json, event.event_id))
@@ -797,10 +789,10 @@ class PersistEventsStore:
                 {
                     "event_id": event.event_id,
                     "room_id": event.room_id,
-                    "internal_metadata": encode_json(
+                    "internal_metadata": frozendict_json_encoder.encode(
                         event.internal_metadata.get_dict()
                     ),
-                    "json": encode_json(event_dict(event)),
+                    "json": frozendict_json_encoder.encode(event_dict(event)),
                     "format_version": event.format_version,
                 }
                 for event, _ in events_and_contexts
diff --git a/synapse/storage/databases/main/stream.py b/synapse/storage/databases/main/stream.py
index 37249f1e3f..1d27439536 100644
--- a/synapse/storage/databases/main/stream.py
+++ b/synapse/storage/databases/main/stream.py
@@ -546,7 +546,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore, metaclass=abc.ABCMeta):
 
     async def get_room_event_before_stream_ordering(
         self, room_id: str, stream_ordering: int
-    ) -> Tuple[int, int, str]:
+    ) -> Optional[Tuple[int, int, str]]:
         """Gets details of the first event in a room at or before a stream ordering
 
         Args:
diff --git a/synapse/storage/util/id_generators.py b/synapse/storage/util/id_generators.py
index 02fbb656e8..ec356b2e4f 100644
--- a/synapse/storage/util/id_generators.py
+++ b/synapse/storage/util/id_generators.py
@@ -421,7 +421,7 @@ class MultiWriterIdGenerator:
             self._unfinished_ids.discard(next_id)
             self._finished_ids.add(next_id)
 
-            new_cur = None
+            new_cur = None  # type: Optional[int]
 
             if self._unfinished_ids:
                 # If there are unfinished IDs then the new position will be the