content: Support the new class of channel wildcard mentions

For channel wildcard mentions, the class in the corresponding HTML used
to be the same as the user mentions (class="user-mention"), but now
there's an additional class added. Now it looks like the following:
class="user-mention channel-wildcard-mention".

Fixes: zulip#1064

Author: sm-sayedi

lib/model/content.dart

@@ -713,7 +713,7 @@ class UserMentionNode extends InlineContainerNode {
   // (e.g., silent mentions' text lacks a leading "@"),
   // and we show that text in the same style for all types of @-mention.
   // We'll need these for implementing the post-2023 Zulip design, though.
-  //   final UserMentionType mentionType; // TODO(#646)
+    // final UserMentionType mentionType; // TODO(#646)
   //   final bool isSilent; // TODO(#647)
 }
 
@@ -880,16 +880,28 @@ class _ZulipContentParser {
         || classes.contains('user-group-mention'));
     int i = 0;
 
+    if (i >= classes.length) return null;
+    bool isChannelWildcardClassIncluded = false;
+    if (classes[i] == 'channel-wildcard-mention') {
+      // A newly-added class for channel wildcard mentions.
+      // See: https://github.com/zulip/zulip/pull/31075
+      i++;
+      isChannelWildcardClassIncluded = true;
+    }
+
     if (i >= classes.length) return null;
     if (classes[i] == 'silent') {
       // A silent @-mention.  We ignore this flag; see [UserMentionNode].
       i++;
     }
 
     if (i >= classes.length) return null;
-    if (classes[i] == 'user-mention' || classes[i] == 'user-group-mention') {
+    if (classes[i] == 'user-mention' ||
+       (classes[i] == 'user-group-mention' && !isChannelWildcardClassIncluded)) {
       // The class we already knew we'd find before we called this function.
       // We ignore the distinction between these; see [UserMentionNode].
+      // Also, we don't expect "user-group-mention" and "channel-wildcard-mention"
+      // to be in the list at the same time.
       i++;
     }
 
@@ -923,6 +935,14 @@ class _ZulipContentParser {
   // as a member of the list.
   static final _userMentionClassNameRegexp = RegExp(
     r"(^| )" r"user(?:-group)?-mention" r"( |$)");
+  // static final _userMentionClassNameRegexp = () {
+  //   // This matches the classes `user-mention`, `user-group-mention`,
+  //   // or `user-mention channel-wildcard-mention`, plus an optional
+  //   // class `silent`, appearing in either order.
+  //   const mentionClass = r"user(?:-group)?-mention|"
+  //                         "(?:user-mention channel-wildcard-mention)";
+  //   return RegExp("^(?:$mentionClass)(?: silent)?|silent (?:$mentionClass)\$");
+  // }();
 
   static final _emojiClassNameRegexp = () {
     const specificEmoji = r"emoji(?:-[0-9a-f]+)+";

test/model/content_test.dart

@@ -139,6 +139,48 @@ class ContentExample {
     '<p><span class="silent user-group-mention" data-user-group-id="186">test-empty</span></p>',
     const UserMentionNode(nodes: [TextNode('test-empty')]));
 
+  static final channelWildcardMentionPlain = ContentExample.inline(
+    'plain channel wildcard @-mention',
+    "@**all**",
+    expectedText: '@all',
+    '<p><span class="user-mention channel-wildcard-mention" data-user-id="*">@all</span></p>',
+    const UserMentionNode(nodes: [TextNode('@all')]));
+
+  static final channelWildcardMentionSilent = ContentExample.inline(
+    'silent channel wildcard @-mention',
+    "@_**everyone**",
+    expectedText: 'everyone',
+    '<p><span class="user-mention channel-wildcard-mention silent" data-user-id="*">everyone</span></p>',
+    const UserMentionNode(nodes: [TextNode('everyone')]));
+
+  static final channelWildcardMentionSilentClassOrderReversed = ContentExample.inline(
+    'silent channel wildcard @-mention, class order reversed',
+    "@_**channel**", // (hypothetical server variation)
+    expectedText: 'channel',
+    '<p><span class="silent user-mention channel-wildcard-mention" data-user-id="*">channel</span></p>',
+    const UserMentionNode(nodes: [TextNode('channel')]));
+
+  static final legacyChannelWildcardMentionPlain = ContentExample.inline(
+    'legacy plain channel wildcard @-mention',
+    "@**channel**",
+    expectedText: '@channel',
+    '<p><span class="user-mention" data-user-id="*">@channel</span></p>',
+    const UserMentionNode(nodes: [TextNode('@channel')]));
+
+  static final legacyChannelWildcardMentionSilent = ContentExample.inline(
+    'legacy silent channel wildcard @-mention',
+    "@_**stream**",
+    expectedText: 'stream',
+    '<p><span class="user-mention silent" data-user-id="*">stream</span></p>',
+    const UserMentionNode(nodes: [TextNode('stream')]));
+
+  static final legacyChannelWildcardMentionSilentClassOrderReversed = ContentExample.inline(
+    'legacy silent channel wildcard @-mention, class order reversed',
+    "@_**all**", // (hypothetical server variation)
+    expectedText: 'all',
+    '<p><span class="silent user-mention" data-user-id="*">all</span></p>',
+    const UserMentionNode(nodes: [TextNode('all')]));
+
   static final emojiUnicode = ContentExample.inline(
     'Unicode emoji, encoded in span element',
     ":thumbs_up:",
@@ -1213,7 +1255,13 @@ void main() {
     testParseExample(ContentExample.groupMentionSilent);
     testParseExample(ContentExample.groupMentionSilentClassOrderReversed);
 
-    // TODO test wildcard mentions
+    testParseExample(ContentExample.channelWildcardMentionPlain);
+    testParseExample(ContentExample.channelWildcardMentionSilent);
+    testParseExample(ContentExample.channelWildcardMentionSilentClassOrderReversed);
+
+    testParseExample(ContentExample.legacyChannelWildcardMentionPlain);
+    testParseExample(ContentExample.legacyChannelWildcardMentionSilent);
+    testParseExample(ContentExample.legacyChannelWildcardMentionSilentClassOrderReversed);
   });
 
   testParseExample(ContentExample.emojiUnicode);

test/widgets/content_test.dart

@@ -650,6 +650,12 @@ void main() {
     testContentSmoke(ContentExample.userMentionSilent);
     testContentSmoke(ContentExample.groupMentionPlain);
     testContentSmoke(ContentExample.groupMentionSilent);
+    testContentSmoke(ContentExample.channelWildcardMentionPlain);
+    testContentSmoke(ContentExample.channelWildcardMentionSilent);
+    testContentSmoke(ContentExample.channelWildcardMentionSilentClassOrderReversed);
+    testContentSmoke(ContentExample.legacyChannelWildcardMentionPlain);
+    testContentSmoke(ContentExample.legacyChannelWildcardMentionSilent);
+    testContentSmoke(ContentExample.legacyChannelWildcardMentionSilentClassOrderReversed);
 
     UserMention? findUserMentionInSpan(InlineSpan rootSpan) {
       UserMention? result;