From d8692db1efa893b4b9e22ca0dbd96c64cc8da8c4 Mon Sep 17 00:00:00 2001
From: Zack <night@users.noreply.github.com>
Date: Mon, 20 Jul 2020 17:22:42 -0700
Subject: [PATCH] (parser) use null prototype objects for languages/aliases
 (#2636)

Fix: Discord uses getLanguage to validate that a language specified exists in highlightJS and retrieve metadata about the language for code block highlighting in chat. Because highlightJS returns prototype values instead of the highlight languages themselves, the result is a few different bugs in our clients which expect the return type to be only `Language | undefined`.
---
 CHANGES.md              |  2 ++
 src/highlight.js        |  4 ++--
 test/api/getLanguage.js | 12 ++++++++++++
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/CHANGES.md b/CHANGES.md
index b530661178..c641b19cfd 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -8,10 +8,12 @@ Language Improvements:
 
 - enh(matlab) Add new R2019b `arguments` keyword and fix `enumeration` keyword (#2619) [Andrew Janke][]
 - fix(kotlin) Remove very old keywords and update example code (#2623) [kageru][]
+- fix(night) Prevent object prototypes method values from being returned in `getLanguage` (#2636) [night][]
 
 [Andrew Janke]: https://github.com/apjanke
 [Samia Ali]: https://github.com/samiaab1990
 [kageru]: https://github.com/kageru
+[night]: https://github.com/night
 
 
 ## Version 10.1.1
diff --git a/src/highlight.js b/src/highlight.js
index 4f98f38ea5..b16efe83a0 100644
--- a/src/highlight.js
+++ b/src/highlight.js
@@ -29,9 +29,9 @@ const HLJS = function(hljs) {
 
   // Global internal variables used within the highlight.js library.
   /** @type {Record<string, Language>} */
-  var languages = {};
+  var languages = Object.create(null);
   /** @type {Record<string, string>} */
-  var aliases = {};
+  var aliases = Object.create(null);
   /** @type {HLJSPlugin[]} */
   var plugins = [];
 
diff --git a/test/api/getLanguage.js b/test/api/getLanguage.js
index d2654a4f63..ae14ebb92e 100644
--- a/test/api/getLanguage.js
+++ b/test/api/getLanguage.js
@@ -41,4 +41,16 @@ describe('.getLanguage()', () => {
     result.should.have.property('aliases').with.containEql('cs');
     should.strictEqual(result, hljs.getLanguage('csharp'))
   });
+
+  it('should not succeed for constructor', () => {
+    const result = hljs.getLanguage('constructor');
+
+    should.strictEqual(result, undefined);
+  });
+
+  it('should not succeed for __proto__', () => {
+    const result = hljs.getLanguage('__proto__');
+
+    should.strictEqual(result, undefined);
+  });
 });