From 8c7422958b8cca585e1866cde0d9f9ea6c7a8e43 Mon Sep 17 00:00:00 2001
From: Josh Goebel <me@joshgoebel.com>
Date: Fri, 8 May 2020 02:03:31 -0400
Subject: [PATCH] (fix) `fixMarkup` would rarely destroy markup when `useBR`
 was enabled (#2532)

---
 CHANGES.md            |  1 +
 src/highlight.js      | 12 ++++++------
 test/api/fixmarkup.js | 16 +++++++++++++---
 3 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/CHANGES.md b/CHANGES.md
index 65b4771d18..eacc0a0d0d 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -9,6 +9,7 @@ Parser Engine:
 - (enh) Added `on:end` callback for modes (#2261) [Josh Goebel][]
 - (enh) Added ability to programatically ignore begin and end matches (#2261) [Josh Goebel][]
 - (enh) Added `END_SAME_AS_BEGIN` mode to replace `endSameAsBegin` parser attribute (#2261) [Josh Goebel][]
+- (fix) `fixMarkup` would rarely destroy markup when `useBR` was enabled (#2532) [Josh Goebel][]
 
 Deprecations:
 
diff --git a/src/highlight.js b/src/highlight.js
index c2779be23f..bc34fb4fc3 100644
--- a/src/highlight.js
+++ b/src/highlight.js
@@ -32,7 +32,7 @@ const HLJS = function(hljs) {
   var SAFE_MODE = true;
 
   // Regular expressions used throughout the highlight.js library.
-  var fixMarkupRe = /((^(<[^>]+>|\t|)+|(?:\n)))/gm;
+  var fixMarkupRe = /(^(<[^>]+>|\t|)+|\n)/gm;
 
   var LANGUAGE_NOT_FOUND = "Could not find the language '{}', did you forget to load/include a language module?";
 
@@ -540,13 +540,13 @@ const HLJS = function(hljs) {
       return value;
     }
 
-    return value.replace(fixMarkupRe, function(match, p1) {
-      if (options.useBR && match === '\n') {
-        return '<br>';
+    return value.replace(fixMarkupRe, match => {
+      if (match === '\n') {
+        return options.useBR ? '<br>' : match;
       } else if (options.tabReplace) {
-        return p1.replace(/\t/g, options.tabReplace);
+        return match.replace(/\t/g, options.tabReplace);
       }
-      return '';
+      return match;
     });
   }
 
diff --git a/test/api/fixmarkup.js b/test/api/fixmarkup.js
index 25600926ef..360b6a51e9 100644
--- a/test/api/fixmarkup.js
+++ b/test/api/fixmarkup.js
@@ -5,11 +5,21 @@ const hljs   = require('../../build');
 
 describe('.fixmarkup()', () => {
   after(() => {
-    hljs.configure({ useBR: false })
-  })
+    hljs.configure({ useBR: false });
+  });
+
+  it('should not strip HTML from beginning of strings', () => {
+    hljs.configure({ useBR: true });
+    const value = '<span class="hljs-attr">"some"</span>: \n <span class="hljs-string">"json"</span>';
+    const result = hljs.fixMarkup(value);
+
+    result.should.equal(
+      '<span class="hljs-attr">"some"</span>: <br> <span class="hljs-string">"json"</span>'
+    );
+  });
 
   it('should not add "undefined" to the beginning of the result (#1452)', () => {
-    hljs.configure({ useBR: true })
+    hljs.configure({ useBR: true });
     const value = '{ <span class="hljs-attr">"some"</span>: \n <span class="hljs-string">"json"</span> }';
     const result = hljs.fixMarkup(value);