From 6bc438af4ea065447046f3794488e65a2219e9b5 Mon Sep 17 00:00:00 2001
From: KJyang-0114 <kjyang011487@gmail.com>
Date: Sat, 21 Mar 2026 01:43:48 +0800
Subject: [PATCH] fix(javascript): prevent type assertions with [\ ] or `?`
 from being treated as HTML tags

Fixes #4301 - `<string[]>` breaks highlighting in TypeScript

Root cause: The `isTrulyOpeningTag` function only checked for `<` and `,`
as indicators of non-HTML syntax. When encountering `<string[]>` or
`<string?>`, the `nextChar` after the tag name is `[` or `?`, which
were not recognized as TypeScript type assertion patterns.

Fix: Added `nextChar === "["` and `nextChar === "?"` to the
ignoreMatch conditions, and added `afterMatch` checks for cases with
intervening whitespace (e.g. `<string []>`).

Verified:
- All 1570 existing tests pass
- `<string[]>` no longer treated as HTML tag
- `<string?>` no longer treated as HTML tag
- JSX constructs like `<Component />` still correctly highlighted
- Regular HTML like `<div>` still correctly highlighted
---
 src/languages/javascript.js | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/languages/javascript.js b/src/languages/javascript.js
index 65b60779a4..9f04452a0f 100644
--- a/src/languages/javascript.js
+++ b/src/languages/javascript.js
@@ -47,7 +47,13 @@ export default function(hljs) {
         nextChar === "<" ||
         // the , gives away that this is not HTML
         // `<T, A extends keyof T, V>`
-        nextChar === ","
+        nextChar === "," ||
+        // TypeScript type assertion with array notation
+        // `<string[]>`, `<number[]>`, `<T[]>`, etc.
+        nextChar === "[" ||
+        // TypeScript optional type assertion
+        // `<string?>`, etc.
+        nextChar === "?"
         ) {
         response.ignoreMatch();
         return;
@@ -86,6 +92,13 @@ export default function(hljs) {
           return;
         }
       }
+
+      // TypeScript type assertions with whitespace before brackets or question mark
+      // `<string []>`, `<T []>`, `<string ?>`, `<T ?>`
+      if ((m = afterMatch.match(/^\s*\[\]/)) || (m = afterMatch.match(/^\s+\?/))) {
+        response.ignoreMatch();
+        return;
+      }
     }
   };
   const KEYWORDS = {