From 65f1a46d17cc2f09600859313eba66cab9c88b6f Mon Sep 17 00:00:00 2001
From: "Dustin C. Hatch" <dustin@hatch.name>
Date: Sun, 2 Jul 2017 11:36:48 -0500
Subject: [PATCH] app: Add global error handling

When a controller raises an error, the application now handles it and
ensures that the proper representation is returned to the user-agent.
---
 src/dcow/app.py                  | 23 +++++++++++++++++++++++
 src/dcow/templates/error.html.j2 |  5 +++++
 2 files changed, 28 insertions(+)
 create mode 100644 src/dcow/templates/error.html.j2

diff --git a/src/dcow/app.py b/src/dcow/app.py
index 1a04d96..3a03087 100644
--- a/src/dcow/app.py
+++ b/src/dcow/app.py
@@ -5,8 +5,13 @@ from . import (
     thumbnails,
 )
 import functools
+import logging
 import milla.util
 import os
+import sys
+
+
+log = logging.getLogger(__name__)
 
 
 DEFAULT_CONFIG = {
@@ -53,3 +58,21 @@ class Application(milla.Application):
             request.want = 'xhtml'
         request.ResponseClass = functools.partial(base.VariedResponse, request)
         return request
+
+    def handle_error(self, request):
+        response = request.ResponseClass()
+        e = sys.exc_info()[1]
+        err = {}
+        if isinstance(e, milla.HTTPRedirection):
+            return e
+        elif isinstance(e, milla.WSGIHTTPException):
+            response.status_int = e.code
+            err['code'] = getattr(e, 'errno', e.code)
+            err['message'] = '{}'.format(e)
+        else:
+            log.exception('An unhandled exception occurred:')
+            response.status_int = 500
+            err['code'] = -1
+            err['message'] = 'An unknown error has occurred'
+        response.set_payload('error.html.j2', {'error': err})
+        return response
diff --git a/src/dcow/templates/error.html.j2 b/src/dcow/templates/error.html.j2
new file mode 100644
index 0000000..7085193
--- /dev/null
+++ b/src/dcow/templates/error.html.j2
@@ -0,0 +1,5 @@
+{% extends "base.html.j2" %}
+{% block body -%}
+<h2>Error</h2>
+<div>{{ error.message }}</div>
+{% endblock body -%}