narrow_filter: Pass message/flags to narrow_filter.

We no longer pass in a big opaque event to narrow_filter
(which is inside build_narrow_filter). We instead explicitly
pass in message and flags. This leads to a bit more type
safety, and it's also more flexible. There's no reason to
build an entire event just to see if a message belongs to
a narrow.

The changes to the test work around the fact that the fixtures
are sloppy with types. I plan a subsequent commit to clean
up those tests significantly.

zerver/lib/narrow.py

@@ -9,7 +9,6 @@ from typing import (
     Generic,
     Iterable,
     List,
-    Mapping,
     Optional,
     Sequence,
     Set,
@@ -23,6 +22,7 @@ from django.conf import settings
 from django.core.exceptions import ValidationError
 from django.db import connection
 from django.utils.translation import gettext as _
+from mypy_extensions import NamedArg
 from sqlalchemy.dialects import postgresql
 from sqlalchemy.engine import Connection, Row
 from sqlalchemy.sql import (
@@ -132,14 +132,14 @@ def is_web_public_narrow(narrow: Optional[Iterable[Dict[str, Any]]]) -> bool:
     )
 
 
-def build_narrow_filter(narrow: Collection[Sequence[str]]) -> Callable[[Mapping[str, Any]], bool]:
+def build_narrow_filter(
+    narrow: Collection[Sequence[str]],
+) -> Callable[[NamedArg(Dict[str, Any], "message"), NamedArg(List[str], "flags")], bool]:
     """Changes to this function should come with corresponding changes to
     NarrowLibraryTest."""
     check_supported_events_narrow_filter(narrow)
 
-    def narrow_filter(event: Mapping[str, Any]) -> bool:
-        message = event["message"]
-        flags = event["flags"]
+    def narrow_filter(*, message: Dict[str, Any], flags: List[str]) -> bool:
         for element in narrow:
             operator = element[0]
             operand = element[1]

zerver/tests/test_message_fetch.py

@@ -603,9 +603,21 @@ class NarrowLibraryTest(ZulipTestCase):
             reject_events = scenario["reject_events"]
             narrow_filter = build_narrow_filter(narrow)
             for e in accept_events:
-                self.assertTrue(narrow_filter(e))
+                message = e["message"]
+                flags = e["flags"]
+                if message is None:
+                    message = {}
+                if flags is None:
+                    flags = []
+                self.assertTrue(narrow_filter(message=message, flags=flags))
             for e in reject_events:
-                self.assertFalse(narrow_filter(e))
+                message = e["message"]
+                flags = e["flags"]
+                if message is None:
+                    message = {}
+                if flags is None:
+                    flags = []
+                self.assertFalse(narrow_filter(message=message, flags=flags))
 
     def test_build_narrow_filter_invalid(self) -> None:
         with self.assertRaises(JsonableError):

zerver/tornado/event_queue.py

@@ -226,7 +226,7 @@ class ClientDescriptor:
                 # older servers that don't support user_topic.
                 return False
         if event["type"] == "message":
-            return self.narrow_filter(event)
+            return self.narrow_filter(message=event["message"], flags=event["flags"])
         if event["type"] == "typing" and "stream_id" in event:
             # Typing notifications for stream messages are only
             # delivered if the stream_typing_notifications