From f80d84e22e6ff27b43e1535e2b9c8699307c88d1 Mon Sep 17 00:00:00 2001
From: Kyle Kelley <rgbkrk@gmail.com>
Date: Mon, 25 Sep 2017 21:38:52 -0700
Subject: [PATCH] prevent mutation on vdom elements

---
 notebook/static/notebook/js/object-to-preact.js | 12 ++++++++++--
 notebook/static/notebook/js/outputarea.js       |  5 ++---
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/notebook/static/notebook/js/object-to-preact.js b/notebook/static/notebook/js/object-to-preact.js
index 05e1b28c41..d3dddcd5db 100644
--- a/notebook/static/notebook/js/object-to-preact.js
+++ b/notebook/static/notebook/js/object-to-preact.js
@@ -93,8 +93,16 @@ define(function() {
       } else if (typeof item === "string") {
         result.push(item);
       } else if (typeof item === "object") {
-        const keyedItem = item;
-        item.key = i;
+        const keyedItem = {
+          tagName: item.tagName,
+          attributes: item.attributes,
+          children: item.children
+        };
+        if (item.attributes && item.attributes.key) {
+          keyedItem.key = item.attributes.key;
+        } else {
+          keyedItem.key = i;
+        }
         result.push(objectToPreactElement(keyedItem));
       } else {
         console.warn("invalid vdom data passed", item);
diff --git a/notebook/static/notebook/js/outputarea.js b/notebook/static/notebook/js/outputarea.js
index 83702c827f..ed3b819441 100644
--- a/notebook/static/notebook/js/outputarea.js
+++ b/notebook/static/notebook/js/outputarea.js
@@ -3,7 +3,6 @@
 
 define([
     'jquery',
-    'underscore',
     'base/js/utils',
     'base/js/i18n',
     'base/js/security',
@@ -12,7 +11,7 @@ define([
     'notebook/js/mathjaxutils',
     'notebook/js/object-to-preact',
     'components/marked/lib/marked',
-], function($, _, utils, i18n, security, keyboard, configmod, mathjaxutils, otp, marked) {
+], function($, utils, i18n, security, keyboard, configmod, mathjaxutils, otp, marked) {
     "use strict";
 
     /**
@@ -714,7 +713,7 @@ define([
         );
 
         element.append(toinsert);
-        preact.render(otp.objectToPreactElement(_.clone(vdom)), toinsert[0]);
+        preact.render(otp.objectToPreactElement(vdom), toinsert[0]);
 
         return toinsert;
      };