Fix characters being emojified even when using Variation Selector 15 (text) (#20949)

app/javascript/mastodon/features/emoji/__tests__/emoji-test.js

@@ -74,9 +74,9 @@ describe('emoji', () => {
         .toEqual('<span class="invisible">😄<br>😴</span><img draggable="false" class="emojione" alt="😇" title=":innocent:" src="/emoji/1f607.svg">');
     });
 
-    it('skips the textual presentation VS15 character', () => {
+    it('does not emojify emojis with textual presentation VS15 character', () => {
       expect(emojify('✴︎')) // This is U+2734 EIGHT POINTED BLACK STAR then U+FE0E VARIATION SELECTOR-15
-        .toEqual('<img draggable="false" class="emojione" alt="✴" title=":eight_pointed_black_star:" src="/emoji/2734_border.svg">');
+        .toEqual('✴︎');
     });
 
     it('does an simple emoji properly', () => {

app/javascript/mastodon/features/emoji/emoji.js

@@ -20,13 +20,18 @@ const emojiFilename = (filename) => {
 };
 
 const emojifyTextNode = (node, customEmojis) => {
+  const VS15 = 0xFE0E;
+  const VS16 = 0xFE0F;
+
   let str = node.textContent;
 
   const fragment = new DocumentFragment();
+  let i = 0;
 
   for (;;) {
-    let match, i = 0;
+    let match;
 
+    // Skip to the next potential emoji to replace
     if (customEmojis === null) {
       while (i < str.length && !(match = trie.search(str.slice(i)))) {
         i += str.codePointAt(i) < 65536 ? 1 : 2;
@@ -37,13 +42,17 @@ const emojifyTextNode = (node, customEmojis) => {
       }
     }
 
-    let rend, replacement = null;
+    // We reached the end of the string, nothing to replace
     if (i === str.length) {
       break;
-    } else if (str[i] === ':') {
-      if (!(() => {
-        rend = str.indexOf(':', i + 1) + 1;
-        if (!rend) return false; // no pair of ':'
+    }
+
+    let rend, replacement = null;
+    if (str[i] === ':') { // Potentially the start of a custom emoji shortcode
+      if (!(rend = str.indexOf(':', i + 1) + 1)) {
+        continue; // no pair of ':'
+      }
+
       const shortname = str.slice(i, rend);
       // now got a replacee as ':shortname:'
       // if you want additional emoji handler, add statements below which set replacement and return true.
@@ -57,31 +66,34 @@ const emojifyTextNode = (node, customEmojis) => {
         replacement.setAttribute('src', filename);
         replacement.setAttribute('data-original', customEmojis[shortname].url);
         replacement.setAttribute('data-static', customEmojis[shortname].static_url);
-          return true;
+      } else {
+        continue;
       }
-        return false;
-      })()) rend = ++i;
     } else { // matched to unicode emoji
+      rend = i + match.length;
+
+      // If the matched character was followed by VS15 (for selecting text presentation), skip it.
+      if (str.codePointAt(rend - 1) !== VS16 && str.codePointAt(rend) === VS15) {
+        i = rend + 1;
+        continue;
+      }
+
       const { filename, shortCode } = unicodeMapping[match];
       const title = shortCode ? `:${shortCode}:` : '';
+
       replacement = document.createElement('img');
       replacement.setAttribute('draggable', 'false');
       replacement.setAttribute('class', 'emojione');
       replacement.setAttribute('alt', match);
       replacement.setAttribute('title', title);
       replacement.setAttribute('src', `${assetHost}/emoji/${emojiFilename(filename)}.svg`);
-      rend = i + match.length;
-      // If the matched character was followed by VS15 (for selecting text presentation), skip it.
-      if (str.codePointAt(rend) === 65038) {
-        rend += 1;
-      }
     }
 
+    // Add the processed-up-to-now string and the emoji replacement
     fragment.append(document.createTextNode(str.slice(0, i)));
-    if (replacement) {
     fragment.append(replacement);
-    }
     str = str.slice(rend);
+    i = 0;
   }
 
   fragment.append(document.createTextNode(str));