push_notifications: Show EMPTY_TOPIC_FALLBACK_NAME for topic="".

This commit adds support to display `Message.EMPTY_TOPIC_FALLBACK_NAME`
value (translated) in the push notifications for topics having the
actual value of empty string.

Fixes part of #32996.

zerver/lib/push_notifications.py

@@ -47,6 +47,7 @@ from zerver.lib.remote_server import (
 from zerver.lib.soft_deactivation import soft_reactivate_if_personal_notification
 from zerver.lib.tex import change_katex_to_raw_latex
 from zerver.lib.timestamp import datetime_to_timestamp
+from zerver.lib.topic import get_topic_display_name
 from zerver.lib.url_decoding import is_same_server_message_link
 from zerver.lib.users import check_can_access_user
 from zerver.models import (
@@ -992,7 +993,7 @@ def get_message_payload(
         data["recipient_type"] = "stream"
         data["stream"] = get_message_stream_name_from_database(message)
         data["stream_id"] = message.recipient.type_id
-        data["topic"] = message.topic_name()
+        data["topic"] = get_topic_display_name(message.topic_name(), user_profile.default_language)
     elif message.recipient.type == Recipient.DIRECT_MESSAGE_GROUP:
         data["recipient_type"] = "private"
         data["pm_users"] = direct_message_group_users(message.recipient.id)
@@ -1002,7 +1003,7 @@ def get_message_payload(
     return data
 
 
-def get_apns_alert_title(message: Message) -> str:
+def get_apns_alert_title(message: Message, language: str) -> str:
     """
     On an iOS notification, this is the first bolded line.
     """
@@ -1012,7 +1013,8 @@ def get_apns_alert_title(message: Message) -> str:
         return ", ".join(sorted(r["full_name"] for r in recipients))
     elif message.is_stream_message():
         stream_name = get_message_stream_name_from_database(message)
-        return f"#{stream_name} > {message.topic_name()}"
+        topic_display_name = get_topic_display_name(message.topic_name(), language)
+        return f"#{stream_name} > {topic_display_name}"
     # For 1:1 direct messages, we just show the sender name.
     return message.sender.full_name
 
@@ -1105,7 +1107,7 @@ def get_message_payload_apns(
         content, _ = truncate_content(get_mobile_push_content(message.rendered_content))
         apns_data = {
             "alert": {
-                "title": get_apns_alert_title(message),
+                "title": get_apns_alert_title(message, user_profile.default_language),
                 "subtitle": get_apns_alert_subtitle(
                     message, trigger, user_profile, mentioned_user_group_name, can_access_sender
                 ),

zerver/tests/test_push_notifications.py

@@ -4196,13 +4196,21 @@ class TestGetAPNsPayload(PushNotificationTest):
         self.assertDictEqual(payload, expected)
         mock_push_notifications.assert_called()
 
-    def _test_get_message_payload_apns_stream_message(self, trigger: str) -> None:
+    def _test_get_message_payload_apns_stream_message(
+        self, trigger: str, empty_string_topic: bool = False
+    ) -> None:
         stream = Stream.objects.filter(name="Verona").get()
         message = self.get_message(Recipient.STREAM, stream.id, stream.realm_id)
+        topic_display_name = message.topic_name()
+        if empty_string_topic:
+            message.set_topic_name("")
+            message.save()
+            topic_display_name = Message.EMPTY_TOPIC_FALLBACK_NAME
+
         payload = get_message_payload_apns(self.sender, message, trigger)
         expected = {
             "alert": {
-                "title": "#Verona > Test topic",
+                "title": f"#Verona > {topic_display_name}",
                 "subtitle": "King Hamlet:",
                 "body": message.content,
             },
@@ -4216,7 +4224,7 @@ class TestGetAPNsPayload(PushNotificationTest):
                     "sender_id": self.sender.id,
                     "stream": stream.name,
                     "stream_id": stream.id,
-                    "topic": message.topic_name(),
+                    "topic": topic_display_name,
                     "server": settings.EXTERNAL_HOST,
                     "realm_id": self.sender.realm.id,
                     "realm_name": self.sender.realm.name,
@@ -4235,6 +4243,11 @@ class TestGetAPNsPayload(PushNotificationTest):
     def test_get_message_payload_apns_followed_topic_message(self) -> None:
         self._test_get_message_payload_apns_stream_message(NotificationTriggers.FOLLOWED_TOPIC_PUSH)
 
+    def test_get_message_payload_apns_empty_string_topic(self) -> None:
+        self._test_get_message_payload_apns_stream_message(
+            NotificationTriggers.STREAM_PUSH, empty_string_topic=True
+        )
+
     def test_get_message_payload_apns_stream_mention(self) -> None:
         user_profile = self.example_user("othello")
         stream = Stream.objects.filter(name="Verona").get()
@@ -4469,9 +4482,11 @@ class TestGetGCMPayload(PushNotificationTest):
         truncate_content: bool = False,
         mentioned_user_group_id: int | None = None,
         mentioned_user_group_name: str | None = None,
+        empty_string_topic: bool = False,
     ) -> None:
         stream = Stream.objects.filter(name="Verona").get()
         message = self.get_message(Recipient.STREAM, stream.id, stream.realm_id)
+
         content = message.content
         if truncate_content:
             message.content = "a" * 210
@@ -4479,6 +4494,12 @@ class TestGetGCMPayload(PushNotificationTest):
             message.save()
             content = "a" * 200 + "…"
 
+        topic_display_name = message.topic_name()
+        if empty_string_topic:
+            message.set_topic_name("")
+            message.save()
+            topic_display_name = Message.EMPTY_TOPIC_FALLBACK_NAME
+
         hamlet = self.example_user("hamlet")
         payload, gcm_options = get_message_payload_gcm(
             hamlet, message, mentioned_user_group_id, mentioned_user_group_name
@@ -4502,7 +4523,7 @@ class TestGetGCMPayload(PushNotificationTest):
             "recipient_type": "stream",
             "stream": stream.name,
             "stream_id": stream.id,
-            "topic": message.topic_name(),
+            "topic": topic_display_name,
         }
 
         if mentioned_user_group_id is not None:
@@ -4533,6 +4554,9 @@ class TestGetGCMPayload(PushNotificationTest):
             mentioned_user_group_name="mobile_team",
         )
 
+    def test_get_message_payload_gcm_empty_string_topic(self) -> None:
+        self._test_get_message_payload_gcm_stream_message(empty_string_topic=True)
+
     def test_get_message_payload_gcm_direct_message(self) -> None:
         message = self.get_message(
             Recipient.PERSONAL,