From 56a641974e7edb49c63beb08574731a5b152b4f7 Mon Sep 17 00:00:00 2001
From: Ryan Marren <rymarr@tuta.io>
Date: Sun, 29 Jul 2018 14:57:23 -0400
Subject: [PATCH 1/4] Back-end errors propagated to front.

---
 dash/dash.py | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/dash/dash.py b/dash/dash.py
index 44fad1efee..41fc50d0a2 100644
--- a/dash/dash.py
+++ b/dash/dash.py
@@ -8,6 +8,7 @@
 import pkgutil
 import warnings
 import re
+import traceback
 
 from functools import wraps
 
@@ -16,6 +17,8 @@
 import flask
 from flask import Flask, Response
 from flask_compress import Compress
+from flask import got_request_exception
+from flask_socketio import SocketIO
 
 from .dependencies import Event, Input, Output, State
 from .resources import Scripts, Css
@@ -114,6 +117,7 @@ def __init__(
         self.index_string = index_string
         self._meta_tags = meta_tags or []
         self._favicon = None
+        self._errors = ""
 
         if compress:
             # gzip
@@ -760,4 +764,24 @@ def run_server(self,
                    port=8050,
                    debug=False,
                    **flask_run_options):
-        self.server.run(port=port, debug=debug, **flask_run_options)
+        if debug:
+            socketio = SocketIO(self.server)
+
+            @got_request_exception.connect_via(self.server)
+            def when_dash_gets_exception(server, exception, **extra):
+                socketio.emit(
+                    'error',
+                    {
+                        'errorType': type(exception).__name__,
+                        'errorMessage': str(exception),
+                        'errorTraceback': traceback.format_exc(),
+                    },
+                    namespace=(
+                       '{}_dash-errors'
+                       .format(self.config['routes_pathname_prefix'])
+                    )
+                )
+
+            socketio.run(self.server, port=port, debug=debug)
+        else:
+            self.server.run(port=port, debug=debug, **flask_run_options)

From b287e89bc7fcffa30829c0e7f953d312e48448d3 Mon Sep 17 00:00:00 2001
From: Ryan Marren <rymarr@tuta.io>
Date: Sun, 29 Jul 2018 17:12:43 -0400
Subject: [PATCH 2/4] Add Flask-SocketIO dependency.

---
 requirements.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/requirements.txt b/requirements.txt
index 4eb352abdc..2a7c86ab36 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -10,6 +10,7 @@ enum34==1.1.6
 Flask==0.12
 Flask-Compress==1.4.0
 Flask-SeaSurf==0.2.2
+Flask-SocketIO==3.0.1
 funcsigs==1.0.2
 functools32==3.2.3.post2
 ipdb==0.10.2

From b68deadb2b878cd5dac3fe72575c4cd4114bfee4 Mon Sep 17 00:00:00 2001
From: Ryan Marren <rymarr@tuta.io>
Date: Sun, 29 Jul 2018 17:16:55 -0400
Subject: [PATCH 3/4] Add Flask-SocketIO to dev depencencies as well.

---
 dev-requirements.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/dev-requirements.txt b/dev-requirements.txt
index f667e354c3..1701b91b18 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -13,3 +13,4 @@ plotly>=2.0.8
 requests[security]
 flake8
 pylint==1.9.2
+Flask-SocketIO==3.0.1

From ffcd49a6166cd65ee45cf6627fc5341fd8f3752b Mon Sep 17 00:00:00 2001
From: Ryan Marren <rymarr@tuta.io>
Date: Sun, 29 Jul 2018 22:04:19 -0400
Subject: [PATCH 4/4] Pylint fixes.

---
 dash/dash.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/dash/dash.py b/dash/dash.py
index 41fc50d0a2..73e9060023 100644
--- a/dash/dash.py
+++ b/dash/dash.py
@@ -15,9 +15,8 @@
 import plotly
 import dash_renderer
 import flask
-from flask import Flask, Response
+from flask import Flask, Response, got_request_exception
 from flask_compress import Compress
-from flask import got_request_exception
 from flask_socketio import SocketIO
 
 from .dependencies import Event, Input, Output, State
@@ -768,6 +767,7 @@ def run_server(self,
             socketio = SocketIO(self.server)
 
             @got_request_exception.connect_via(self.server)
+            # pylint: disable=unused-variable
             def when_dash_gets_exception(server, exception, **extra):
                 socketio.emit(
                     'error',
@@ -777,8 +777,8 @@ def when_dash_gets_exception(server, exception, **extra):
                         'errorTraceback': traceback.format_exc(),
                     },
                     namespace=(
-                       '{}_dash-errors'
-                       .format(self.config['routes_pathname_prefix'])
+                        '{}_dash-errors'
+                        .format(self.config['routes_pathname_prefix'])
                     )
                 )