From 6f718c44367bf5607d848e0d37b51f097b73d8f4 Mon Sep 17 00:00:00 2001
From: philippe <t4rk@outlook.com>
Date: Tue, 3 May 2022 12:58:39 -0400
Subject: [PATCH 1/3] Fix debugger html check.

---
 .../src/components/error/FrontEnd/FrontEndError.react.js   | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/dash/dash-renderer/src/components/error/FrontEnd/FrontEndError.react.js b/dash/dash-renderer/src/components/error/FrontEnd/FrontEndError.react.js
index 49939ea1de..83c638d4e0 100644
--- a/dash/dash-renderer/src/components/error/FrontEnd/FrontEndError.react.js
+++ b/dash/dash-renderer/src/components/error/FrontEnd/FrontEndError.react.js
@@ -109,9 +109,10 @@ function UnconnectedErrorContent({error, base}) {
                 </div>
             )}
             {/* Backend Error */}
-            {typeof error.html !== 'string' ? null : error.html.indexOf(
-                  '<!DOCTYPE'
-              ) === 0 ? (
+            {typeof error.html !== 'string' ? null : error.html
+                  .split()[0]
+                  .toLowerCase()
+                  .startsWith('<!doctype') ? (
                 <div className='dash-be-error__st'>
                     <div className='dash-backend-error'>
                         {/* Embed werkzeug debugger in an iframe to prevent

From 9a91e5edd8beb101361214966ff13692f1f7321b Mon Sep 17 00:00:00 2001
From: philippe <t4rk@outlook.com>
Date: Tue, 3 May 2022 13:30:39 -0400
Subject: [PATCH 2/3] Ignore percy retry errors.

---
 dash/testing/browser.py | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/dash/testing/browser.py b/dash/testing/browser.py
index 63ea244592..4449f0abb5 100644
--- a/dash/testing/browser.py
+++ b/dash/testing/browser.py
@@ -5,6 +5,7 @@
 import logging
 import warnings
 import percy
+import requests
 
 from selenium import webdriver
 from selenium.webdriver.support import expected_conditions as EC
@@ -188,8 +189,14 @@ def percy_snapshot(
             """
             )
 
+        try:
             self.percy_runner.snapshot(name=snapshot_name, widths=widths)
+        except requests.HTTPError as err:
+            # Ignore retries.
+            if err.request.status_code != 400:
+                raise err
 
+        if convert_canvases:
             self.driver.execute_script(
                 """
                 const stash = window._canvasStash;
@@ -204,9 +211,6 @@ def percy_snapshot(
             """
             )
 
-        else:
-            self.percy_runner.snapshot(name=snapshot_name, widths=widths)
-
     def take_snapshot(self, name):
         """Hook method to take snapshot when a selenium test fails. The
         snapshot is placed under.

From 773ad6780358e2aaf2e3c2d6cf79efbedcdd9f6a Mon Sep 17 00:00:00 2001
From: philippe <t4rk@outlook.com>
Date: Tue, 3 May 2022 13:36:22 -0400
Subject: [PATCH 3/3] Update changelog.

---
 CHANGELOG.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f46cc62f8f..8d60cf432a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,8 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 - [#1976](https://github.com/plotly/dash/pull/1976) Fix [#1962](https://github.com/plotly/dash/issues/1962) in which DatePickerSingle and DatePickerRange are extremely slow when provided a long list of disabled_days.
 
+- [#2035](https://github.com/plotly/dash/pull/2035) Fix [#2033](https://github.com/plotly/dash/issues/2033) In-App error reporting does not render HTML.
+
 ### Changed
 
 - [#2016](https://github.com/plotly/dash/pull/2016) Drop the 375px width from default percy_snapshot calls, keep only 1280px