compose: Handle hint texts when topic is empty

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

lib/widgets/compose_box.dart

@@ -593,7 +593,8 @@ class _StreamContentInputState extends State<_StreamContentInput> {
     if (store.realmMandatoryTopics && widget.controller.topic.isTopicVacuous) {
       topicDisplayName = null;
     } else {
-      topicDisplayName = topic.displayName;
+      // ignore: dead_null_aware_expression // null topic names soon to be enabled
+      topicDisplayName = topic.displayName ?? store.realmEmptyTopicDisplayName;
     }
 
     return _ContentInput(
@@ -662,7 +663,8 @@ class _FixedDestinationContentInput extends StatelessWidget {
         final streamName = store.streams[streamId]?.name
           ?? zulipLocalizations.unknownChannelName;
         return zulipLocalizations.composeBoxChannelTopicContentHint(
-          '#$streamName > ${topic.displayName}');
+          // ignore: dead_null_aware_expression // null topic names soon to be enabled
+          '#$streamName > ${topic.displayName ?? store.realmEmptyTopicDisplayName}');
 
       case DmNarrow(otherRecipientIds: []): // The self-1:1 thread.
         return zulipLocalizations.composeBoxSelfDmContentHint;

test/widgets/compose_box_test.dart

@@ -47,15 +47,18 @@ void main() {
     List<User> otherUsers = const [],
     List<ZulipStream> streams = const [],
     bool? mandatoryTopics,
+    int? zulipFeatureLevel,
   }) async {
     if (narrow case ChannelNarrow(:var streamId) || TopicNarrow(: var streamId)) {
       assert(streams.any((stream) => stream.streamId == streamId),
         'Add a channel with "streamId" the same as of $narrow.streamId to the store.');
     }
     addTearDown(testBinding.reset);
     selfUser ??= eg.selfUser;
-    final selfAccount = eg.account(user: selfUser);
+    zulipFeatureLevel ??= eg.futureZulipFeatureLevel;
+    final selfAccount = eg.account(user: selfUser, zulipFeatureLevel: zulipFeatureLevel);
     await testBinding.globalStore.add(selfAccount, eg.initialSnapshot(
+      zulipFeatureLevel: zulipFeatureLevel,
       realmMandatoryTopics: mandatoryTopics,
     ));
 
@@ -327,12 +330,14 @@ void main() {
     Future<void> prepare(WidgetTester tester, {
       required Narrow narrow,
       bool? mandatoryTopics,
+      int? zulipFeatureLevel,
     }) async {
       await prepareComposeBox(tester,
         narrow: narrow,
         otherUsers: [eg.otherUser, eg.thirdUser],
         streams: [channel],
-        mandatoryTopics: mandatoryTopics);
+        mandatoryTopics: mandatoryTopics,
+        zulipFeatureLevel: zulipFeatureLevel);
     }
 
     /// This checks the input's configured hint text without regard to whether
@@ -355,8 +360,18 @@ void main() {
 
     group('to ChannelNarrow, topics not mandatory', () {
       testWidgets('with empty topic', (tester) async {
+        final narrow = ChannelNarrow(channel.streamId);
+        await prepare(tester, narrow: narrow, mandatoryTopics: false);
+        await tester.pump();
+        checkComposeBoxHintTexts(tester,
+          topicHintText: 'Topic',
+          contentHintText: 'Message #${channel.name} > ${eg.defaultRealmEmptyTopicDisplayName}');
+      }, skip: true); // null topic names soon to be enabled
+
+      testWidgets('legacy: with empty topic', (tester) async {
         await prepare(tester, narrow: ChannelNarrow(channel.streamId),
-          mandatoryTopics: false);
+          mandatoryTopics: false,
+          zulipFeatureLevel: 333);
         checkComposeBoxHintTexts(tester,
           topicHintText: 'Topic',
           contentHintText: 'Message #${channel.name} > (no topic)');
@@ -381,6 +396,15 @@ void main() {
         checkComposeBoxHintTexts(tester,
           topicHintText: 'Topic',
           contentHintText: 'Message #${channel.name}');
+      }, skip: true); // null topic names soon to be enabled
+
+      testWidgets('legacy: with empty topic', (tester) async {
+        await prepare(tester, narrow: ChannelNarrow(channel.streamId),
+          mandatoryTopics: true,
+          zulipFeatureLevel: 333);
+        checkComposeBoxHintTexts(tester,
+          topicHintText: 'Topic',
+          contentHintText: 'Message #${channel.name}');
       });
 
       testWidgets('with non-empty topic', (tester) async {
@@ -395,13 +419,22 @@ void main() {
       });
     });
 
-    testWidgets('to TopicNarrow', (tester) async {
+    testWidgets('to TopicNarrow with non-empty topic', (tester) async {
       await prepare(tester,
-        narrow: TopicNarrow(channel.streamId, TopicName('topic')));
+        narrow: TopicNarrow(channel.streamId, TopicName('topic')),
+        mandatoryTopics: false);
       checkComposeBoxHintTexts(tester,
         contentHintText: 'Message #${channel.name} > topic');
     });
 
+    testWidgets('to TopicNarrow with empty topic', (tester) async {
+      await prepare(tester,
+        narrow: TopicNarrow(channel.streamId, TopicName('')),
+        mandatoryTopics: false);
+      checkComposeBoxHintTexts(tester, contentHintText:
+        'Message #${channel.name} > ${eg.defaultRealmEmptyTopicDisplayName}');
+    }, skip: true); // null topic names soon to be enabled
+
     testWidgets('to DmNarrow with self', (tester) async {
       await prepare(tester, narrow: DmNarrow.withUser(
         eg.selfUser.userId, selfUserId: eg.selfUser.userId));