typing: Avoid redefinition of incompatible QuerySets.

The pattern of using the same variable to apply filters
or alter the `QuerySet` in other ways might produce `QuerySet`s
with incompatible types. This behavior is not allowed by mypy.

Signed-off-by: Zixuan James Li <p359101898@gmail.com>

zerver/lib/cache.py

@@ -571,8 +571,9 @@ def delete_user_profile_caches(user_profiles: Iterable["UserProfile"]) -> None:
 def delete_display_recipient_cache(user_profile: "UserProfile") -> None:
     from zerver.models import Subscription  # We need to import here to avoid cyclic dependency.
 
-    recipient_ids = Subscription.objects.filter(user_profile=user_profile)
-    recipient_ids = recipient_ids.values_list("recipient_id", flat=True)
+    recipient_ids = Subscription.objects.filter(user_profile=user_profile).values_list(
+        "recipient_id", flat=True
+    )
     keys = [display_recipient_cache_key(rid) for rid in recipient_ids]
     keys.append(display_recipient_bulk_get_users_by_id_cache_key(user_profile.id))
     cache_delete_many(keys)

zerver/lib/email_notifications.py

@@ -560,10 +560,8 @@ def handle_missedmessage_emails(
         usermessage__user_profile_id=user_profile,
         id__in=message_ids,
         usermessage__flags=~UserMessage.flags.read,
-    )
-
-    # Cancel missed-message emails for deleted messages
-    messages = [um for um in messages if um.content != "(deleted)"]
+        # Cancel missed-message emails for deleted messages
+    ).exclude(content="(deleted)")
 
     if not messages:
         return

zerver/lib/events.py

@@ -164,7 +164,7 @@ def fetch_initial_state_data(
         # `max_message_id` is primarily used for generating `local_id`
         # values that are higher than this.  We likely can eventually
         # remove this parameter from the API.
-        user_messages = []
+        user_messages = None
         if user_profile is not None:
             user_messages = (
                 UserMessage.objects.filter(user_profile=user_profile)

zerver/lib/export.py

@@ -1245,8 +1245,8 @@ def export_partial_message_files(
             user_profile_id__in=consented_user_ids
         ).values_list("recipient_id", flat=True)
 
-        recipient_ids = set(public_stream_recipient_ids) | set(consented_recipient_ids)
-        recipient_ids_for_us = get_ids(response["zerver_recipient"]) & recipient_ids
+        recipient_ids_set = set(public_stream_recipient_ids) | set(consented_recipient_ids)
+        recipient_ids_for_us = get_ids(response["zerver_recipient"]) & recipient_ids_set
     else:
         recipient_ids_for_us = get_ids(response["zerver_recipient"])
         # For a full export, we have implicit consent for all users in the export.

zerver/lib/management.py

@@ -140,10 +140,7 @@ server via `ps -ef` or reading bash history. Prefer
         if options["users"] is None:
             return []
         emails = {email.strip() for email in options["users"].split(",")}
-        user_profiles = []
-        for email in emails:
-            user_profiles.append(self.get_user(email, realm))
-        return user_profiles
+        return [self.get_user(email, realm) for email in emails]
 
     def get_user(self, email: str, realm: Optional[Realm]) -> UserProfile:
 

zerver/lib/presence.py

@@ -177,12 +177,12 @@ def get_status_dict_by_realm(
         # a realm with 0 active users.
         return {}
 
-    mobile_query = query_for_ids(
+    mobile_query_ids = query_for_ids(
         query=mobile_query,
         user_ids=user_profile_ids,
         field="user_id",
     )
-    mobile_user_ids = set(mobile_query)
+    mobile_user_ids = set(mobile_query_ids)
 
     return get_status_dicts_for_rows(presence_rows, mobile_user_ids, slim_presence)
 

zerver/lib/user_topics.py

@@ -121,11 +121,9 @@ def exclude_topic_mutes(
         # by not considering topic mutes outside the stream.
         query = query.filter(stream_id=stream_id)
 
-    rows = list(
-        query.values(
-            "recipient_id",
-            "topic_name",
-        )
+    rows = query.values(
+        "recipient_id",
+        "topic_name",
     )
 
     if not rows:
@@ -153,7 +151,6 @@ def build_topic_mute_checker(user_profile: UserProfile) -> Callable[[int, str],
         "recipient_id",
         "topic_name",
     )
-    rows = list(rows)
 
     tups = set()
     for row in rows: