event_schema: Extract check_delete_message.

There is a legacy format where we send
singular "message_id" instead of plural
"message_ids".

Then there are different fields for "private"
and "stream" message types.

zerver/lib/event_schema.py

@@ -218,6 +218,55 @@ default_streams_event = event_dict_type(
 )
 check_default_streams = make_checker(default_streams_event)
 
+delete_message_event = event_dict_type(
+    required_keys=[
+        # force vertical
+        ("type", Equals("delete_message")),
+        ("message_type", EnumType(["private", "stream"])),
+    ],
+    optional_keys=[
+        ("message_id", int),
+        ("message_ids", ListType(int)),
+        ("stream_id", int),
+        ("topic", str),
+        ("recipient_id", int),
+        ("sender_id", int),
+    ],
+)
+_check_delete_message = make_checker(delete_message_event)
+
+
+def check_delete_message(
+    var_name: str,
+    event: Dict[str, object],
+    message_type: str,
+    num_message_ids: int,
+    is_legacy: bool,
+) -> None:
+    _check_delete_message(var_name, event)
+
+    keys = {"id", "type", "message_type"}
+
+    assert event["message_type"] == message_type
+
+    if message_type == "stream":
+        keys |= {"stream_id", "topic"}
+    elif message_type == "private":
+        keys |= {"recipient_id", "sender_id"}
+    else:
+        raise AssertionError("unexpected message_type")
+
+    if is_legacy:
+        assert num_message_ids == 1
+        keys.add("message_id")
+    else:
+        assert isinstance(event["message_ids"], list)
+        assert num_message_ids == len(event["message_ids"])
+        keys.add("message_ids")
+
+    assert set(event.keys()) == keys
+
+
 _hotspot = DictType(
     required_keys=[
         # force vertical

zerver/tests/test_events.py

@@ -97,6 +97,7 @@ from zerver.lib.event_schema import (
     check_custom_profile_fields,
     check_default_stream_groups,
     check_default_streams,
+    check_delete_message,
     check_events_dict,
     check_hotspots,
     check_invites_changed,
@@ -147,14 +148,7 @@ from zerver.lib.test_helpers import (
     stdout_suppressed,
 )
 from zerver.lib.topic import TOPIC_NAME
-from zerver.lib.validator import (
+from zerver.lib.validator import check_bool, check_dict_only, check_int, check_string, equals
-    check_bool,
-    check_dict_only,
-    check_int,
-    check_list,
-    check_string,
-    equals,
-)
 from zerver.models import (
     Attachment,
     Message,
@@ -1566,13 +1560,6 @@ class NormalActionsTest(BaseAction):
         check_subscription_peer_add('events[1]', events[1])
 
     def test_do_delete_message_stream(self) -> None:
-        schema_checker = check_events_dict([
-            ('type', equals('delete_message')),
-            ('message_ids', check_list(check_int, 2)),
-            ('message_type', equals("stream")),
-            ('stream_id', check_int),
-            ('topic', check_string),
-        ])
         hamlet = self.example_user('hamlet')
         msg_id = self.send_stream_message(hamlet, "Verona")
         msg_id_2 = self.send_stream_message(hamlet, "Verona")
@@ -1584,20 +1571,19 @@ class NormalActionsTest(BaseAction):
             lambda: do_delete_messages(self.user_profile.realm, messages),
             state_change_expected=True,
         )
-        schema_checker('events[0]', events[0])
+        check_delete_message(
+            "events[0]",
+            events[0],
+            message_type="stream",
+            num_message_ids=2,
+            is_legacy=False,
+        )
 
     def test_do_delete_message_stream_legacy(self) -> None:
         """
         Test for legacy method of deleting messages which
         sends an event per message to delete to the client.
         """
-        schema_checker = check_events_dict([
-            ('type', equals('delete_message')),
-            ('message_id', check_int),
-            ('message_type', equals("stream")),
-            ('stream_id', check_int),
-            ('topic', check_string),
-        ])
         hamlet = self.example_user('hamlet')
         msg_id = self.send_stream_message(hamlet, "Verona")
         msg_id_2 = self.send_stream_message(hamlet, "Verona")
@@ -1610,16 +1596,15 @@ class NormalActionsTest(BaseAction):
             state_change_expected=True, bulk_message_deletion=False,
             num_events=2
         )
-        schema_checker('events[0]', events[0])
+        check_delete_message(
+            "events[0]",
+            events[0],
+            message_type="stream",
+            num_message_ids=1,
+            is_legacy=True,
+        )
 
     def test_do_delete_message_personal(self) -> None:
-        schema_checker = check_events_dict([
-            ('type', equals('delete_message')),
-            ('message_ids', check_list(check_int, 1)),
-            ('sender_id', check_int),
-            ('message_type', equals("private")),
-            ('recipient_id', check_int),
-        ])
         msg_id = self.send_personal_message(
             self.example_user("cordelia"),
             self.user_profile,
@@ -1630,16 +1615,15 @@ class NormalActionsTest(BaseAction):
             lambda: do_delete_messages(self.user_profile.realm, [message]),
             state_change_expected=True,
         )
-        schema_checker('events[0]', events[0])
+        check_delete_message(
+            "events[0]",
+            events[0],
+            message_type="private",
+            num_message_ids=1,
+            is_legacy=False,
+        )
 
     def test_do_delete_message_personal_legacy(self) -> None:
-        schema_checker = check_events_dict([
-            ('type', equals('delete_message')),
-            ('message_id', check_int),
-            ('sender_id', check_int),
-            ('message_type', equals("private")),
-            ('recipient_id', check_int),
-        ])
         msg_id = self.send_personal_message(
             self.example_user("cordelia"),
             self.user_profile,
@@ -1650,7 +1634,13 @@ class NormalActionsTest(BaseAction):
             lambda: do_delete_messages(self.user_profile.realm, [message]),
             state_change_expected=True, bulk_message_deletion=False
         )
-        schema_checker('events[0]', events[0])
+        check_delete_message(
+            "events[0]",
+            events[0],
+            message_type="private",
+            num_message_ids=1,
+            is_legacy=True,
+        )
 
     def test_do_delete_message_no_max_id(self) -> None:
         user_profile = self.example_user('aaron')