From 44831542bbde3b7a66dadebebb18735eff0d5d1f Mon Sep 17 00:00:00 2001
From: Trevor Buckner <calculuschild@gmail.com>
Date: Mon, 14 Aug 2023 14:30:19 -0400
Subject: [PATCH] Fix unicode Regex miscounting emoji length

Many emojis are 2+ unicode bytes long. The \u tag which allows searching for punctuation also counts emojis as single chars. Slicing the strings into an array restores the correct character count.
---
 src/Tokenizer.ts                 |  7 ++++---
 test/specs/new/emoji_inline.html | 11 +++++++++++
 test/specs/new/emoji_inline.md   | 21 +++++++++++++++++++++
 3 files changed, 36 insertions(+), 3 deletions(-)
 create mode 100644 test/specs/new/emoji_inline.html
 create mode 100644 test/specs/new/emoji_inline.md

diff --git a/src/Tokenizer.ts b/src/Tokenizer.ts
index 769bdb9fd3..f5cd49775e 100644
--- a/src/Tokenizer.ts
+++ b/src/Tokenizer.ts
@@ -625,7 +625,8 @@ export class _Tokenizer {
     const nextChar = match[1] || match[2] || '';
 
     if (!nextChar || !prevChar || this.rules.inline.punctuation.exec(prevChar)) {
-      const lLength = match[0].length - 1;
+      // unicode Regex counts emoji as 1 char; spread into array for proper count (used multiple times below)
+      const lLength = [...match[0]].length - 1;
       let rDelim, rLength, delimTotal = lLength, midDelimTotal = 0;
 
       const endReg = match[0][0] === '*' ? this.rules.inline.emStrong.rDelimAst : this.rules.inline.emStrong.rDelimUnd;
@@ -639,7 +640,7 @@ export class _Tokenizer {
 
         if (!rDelim) continue; // skip single * in __abc*abc__
 
-        rLength = rDelim.length;
+        rLength = [...rDelim].length;
 
         if (match[3] || match[4]) { // found another Left Delim
           delimTotal += rLength;
@@ -658,7 +659,7 @@ export class _Tokenizer {
         // Remove extra characters. *a*** -> *a*
         rLength = Math.min(rLength, rLength + delimTotal + midDelimTotal);
 
-        const raw = src.slice(0, lLength + match.index + rLength + 1);
+        const raw = [...src].slice(0, lLength + match.index + rLength + 1).join('');
 
         // Create `em` if smallest delimiter has odd char count. *a***
         if (Math.min(lLength, rLength) % 2) {
diff --git a/test/specs/new/emoji_inline.html b/test/specs/new/emoji_inline.html
new file mode 100644
index 0000000000..d0b19a20a7
--- /dev/null
+++ b/test/specs/new/emoji_inline.html
@@ -0,0 +1,11 @@
+<p>Situations where it fails:</p>
+<p><strong>test 💁</strong></p>
+<p><strong>💁 test</strong></p>
+<p><strong>🤓 test</strong></p>
+<p><strong>🏖️ test</strong></p>
+<p><strong>🏖️🤓💁 test</strong></p>
+<p>Situations where it works:</p>
+<p>**💁 **</p>
+<p><strong>⚠️ test</strong></p>
+<p>Here, the emoji rendering works, but the text doesn't get rendered in italic.</p>
+<p><em>💁 test</em></p>
\ No newline at end of file
diff --git a/test/specs/new/emoji_inline.md b/test/specs/new/emoji_inline.md
new file mode 100644
index 0000000000..36f6385677
--- /dev/null
+++ b/test/specs/new/emoji_inline.md
@@ -0,0 +1,21 @@
+Situations where it fails:
+
+**test 💁**
+
+**💁 test**
+
+**🤓 test**
+
+**🏖️ test**
+
+**🏖️🤓💁 test**
+
+Situations where it works:
+
+**💁 **
+
+**⚠️ test**
+
+Here, the emoji rendering works, but the text doesn't get rendered in italic.
+
+*💁 test*
\ No newline at end of file