topic_list: Add empty state placeholder for channels with no topics

khanak0509 · gnprice · commit 0347abea628a · 2025-12-16T12:58:21.000-08:00
Fixes: #2003
diff --git a/assets/l10n/app_en.arb b/assets/l10n/app_en.arb
@@ -1492,5 +1492,9 @@
   "zulipAppTitle": "Zulip",
   "@zulipAppTitle": {
     "description": "The name of Zulip. This should be either 'Zulip' or a transliteration."
+  },
+  "topicListEmptyPlaceholderHeader": "There are no topics here yet.",
+  "@topicListEmptyPlaceholderHeader": {
+    "description": "Header text shown when a channel has no topics."
   }
 }
diff --git a/lib/generated/l10n/zulip_localizations.dart b/lib/generated/l10n/zulip_localizations.dart
@@ -2162,6 +2162,12 @@ abstract class ZulipLocalizations {
   /// In en, this message translates to:
   /// **'Zulip'**
   String get zulipAppTitle;
+
+  /// Header text shown when a channel has no topics.
+  ///
+  /// In en, this message translates to:
+  /// **'There are no topics here yet.'**
+  String get topicListEmptyPlaceholderHeader;
 }
 
 class _ZulipLocalizationsDelegate
diff --git a/lib/generated/l10n/zulip_localizations_ar.dart b/lib/generated/l10n/zulip_localizations_ar.dart
@@ -1245,4 +1245,7 @@ class ZulipLocalizationsAr extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_de.dart b/lib/generated/l10n/zulip_localizations_de.dart
@@ -1271,4 +1271,7 @@ class ZulipLocalizationsDe extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_el.dart b/lib/generated/l10n/zulip_localizations_el.dart
@@ -1245,4 +1245,7 @@ class ZulipLocalizationsEl extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_en.dart b/lib/generated/l10n/zulip_localizations_en.dart
@@ -1245,6 +1245,9 @@ class ZulipLocalizationsEn extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
 
 /// The translations for English, as used in the United Kingdom (`en_GB`).
diff --git a/lib/generated/l10n/zulip_localizations_es.dart b/lib/generated/l10n/zulip_localizations_es.dart
@@ -1245,4 +1245,7 @@ class ZulipLocalizationsEs extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_fr.dart b/lib/generated/l10n/zulip_localizations_fr.dart
@@ -1261,4 +1261,7 @@ class ZulipLocalizationsFr extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_he.dart b/lib/generated/l10n/zulip_localizations_he.dart
@@ -1245,4 +1245,7 @@ class ZulipLocalizationsHe extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_hu.dart b/lib/generated/l10n/zulip_localizations_hu.dart
@@ -1245,4 +1245,7 @@ class ZulipLocalizationsHu extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_it.dart b/lib/generated/l10n/zulip_localizations_it.dart
@@ -1265,4 +1265,7 @@ class ZulipLocalizationsIt extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_ja.dart b/lib/generated/l10n/zulip_localizations_ja.dart
@@ -1219,4 +1219,7 @@ class ZulipLocalizationsJa extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_nb.dart b/lib/generated/l10n/zulip_localizations_nb.dart
@@ -1245,4 +1245,7 @@ class ZulipLocalizationsNb extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_pl.dart b/lib/generated/l10n/zulip_localizations_pl.dart
@@ -1264,4 +1264,7 @@ class ZulipLocalizationsPl extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_ru.dart b/lib/generated/l10n/zulip_localizations_ru.dart
@@ -1277,4 +1277,7 @@ class ZulipLocalizationsRu extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_sk.dart b/lib/generated/l10n/zulip_localizations_sk.dart
@@ -1247,4 +1247,7 @@ class ZulipLocalizationsSk extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_sl.dart b/lib/generated/l10n/zulip_localizations_sl.dart
@@ -1286,4 +1286,7 @@ class ZulipLocalizationsSl extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_uk.dart b/lib/generated/l10n/zulip_localizations_uk.dart
@@ -1266,4 +1266,7 @@ class ZulipLocalizationsUk extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
diff --git a/lib/generated/l10n/zulip_localizations_zh.dart b/lib/generated/l10n/zulip_localizations_zh.dart
@@ -1245,6 +1245,9 @@ class ZulipLocalizationsZh extends ZulipLocalizations {
 
   @override
   String get zulipAppTitle => 'Zulip';
+
+  @override
+  String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';
 }
 
 /// The translations for Chinese, as used in China, using the Han script (`zh_Hans_CN`).
diff --git a/lib/widgets/topic_list.dart b/lib/widgets/topic_list.dart
@@ -169,7 +169,11 @@ class _TopicListState extends State<_TopicList> with PerAccountStoreAwareStateMi
       return const Center(child: CircularProgressIndicator());
     }
 
-    // TODO(design) handle the rare case when `lastFetchedTopics` is empty
+    if (lastFetchedTopics!.isEmpty) {
+      final zulipLocalizations = ZulipLocalizations.of(context);
+      return PageBodyEmptyContentPlaceholder(
+        header: zulipLocalizations.topicListEmptyPlaceholderHeader);
+    }
 
     // This is adapted from parts of the build method on [_InboxPageState].
     final topicItems = <_TopicItemData>[];
diff --git a/test/widgets/topic_list_test.dart b/test/widgets/topic_list_test.dart
@@ -124,6 +124,12 @@ void main() {
     check(find.byType(CircularProgressIndicator)).findsNothing();
   });
 
+  testWidgets('shows empty state when no topics', (tester) async {
+    final channel = eg.stream();
+    await prepare(tester, channel: channel, topics: [], messages: []);
+    check(find.text('There are no topics here yet.')).findsOne();
+  });
+
   testWidgets('fetch again when navigating away and back', (tester) async {
     addTearDown(testBinding.reset);
     await testBinding.globalStore.add(eg.selfAccount, eg.initialSnapshot());

Original file line number	Diff line number	Diff line change
`@@ -1492,5 +1492,9 @@`
`1492`	`1492`	`"zulipAppTitle": "Zulip",`
`1493`	`1493`	`"@zulipAppTitle": {`
`1494`	`1494`	`"description": "The name of Zulip. This should be either 'Zulip' or a transliteration."`
	`1495`	`+ },`
	`1496`	`+ "topicListEmptyPlaceholderHeader": "There are no topics here yet.",`
	`1497`	`+ "@topicListEmptyPlaceholderHeader": {`
	`1498`	`+ "description": "Header text shown when a channel has no topics."`
`1495`	`1499`	`}`
`1496`	`1500`	`}`
Original file line number	Diff line number	Diff line change
`@@ -1245,4 +1245,7 @@ class ZulipLocalizationsAr extends ZulipLocalizations {`
`1245`	`1245`
`1246`	`1246`	`@override`
`1247`	`1247`	`String get zulipAppTitle => 'Zulip';`
	`1248`	`+`
	`1249`	`+ @override`
	`1250`	`+ String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';`
`1248`	`1251`	`}`
Original file line number	Diff line number	Diff line change
`@@ -1271,4 +1271,7 @@ class ZulipLocalizationsDe extends ZulipLocalizations {`
`1271`	`1271`
`1272`	`1272`	`@override`
`1273`	`1273`	`String get zulipAppTitle => 'Zulip';`
	`1274`	`+`
	`1275`	`+ @override`
	`1276`	`+ String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';`
`1274`	`1277`	`}`
Original file line number	Diff line number	Diff line change
`@@ -1245,6 +1245,9 @@ class ZulipLocalizationsEn extends ZulipLocalizations {`
`1245`	`1245`
`1246`	`1246`	`@override`
`1247`	`1247`	`String get zulipAppTitle => 'Zulip';`
	`1248`	`+`
	`1249`	`+ @override`
	`1250`	`+ String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';`
`1248`	`1251`	`}`
`1249`	`1252`
`1250`	`1253`	/// The translations for English, as used in the United Kingdom (`en_GB`).
Original file line number	Diff line number	Diff line change
`@@ -1261,4 +1261,7 @@ class ZulipLocalizationsFr extends ZulipLocalizations {`
`1261`	`1261`
`1262`	`1262`	`@override`
`1263`	`1263`	`String get zulipAppTitle => 'Zulip';`
	`1264`	`+`
	`1265`	`+ @override`
	`1266`	`+ String get topicListEmptyPlaceholderHeader => 'There are no topics here yet.';`
`1264`	`1267`	`}`