Ensure dashboard displays error in case of missing or faulty widget, rather...

Ensure dashboard displays error in case of missing or faulty widget, rather than causing the whole application to fail.

django/website/dashboard/templates/dashboard/widget-error.html

+{% load i18n %}
+<div class='panel panel-default'>
+    <div class='panel-heading'>
+        <span class='fa fa-warning fa-fw'></span>
+        <h2>{% trans "Error" %}</h2>
+    </div>
+    <div class='panel-body'>
+        {{ error }}
+    </div>
+</div>

django/website/dashboard/templates/dashboard/widget-missing-template.html

-Missing template_name for widget type {{empty_type}}

django/website/dashboard/templatetags/render_widget.py

+import logging
+
 from django import template
 from django.template.loader import render_to_string
+from django.utils.translation import ugettext_lazy as _
 
-from dashboard.widget_pool import get_widget
+from dashboard.widget_pool import get_widget, MissingWidgetType
 
 
+logger = logging.getLogger(__name__)
 register = template.Library()
 
 
@@ -16,18 +20,40 @@ def render_widget(widget_instance):
     get_context_data then that is used to generate the
     template context.
     """
-    widget = get_widget(widget_instance.widget_type)
+    widget = None
+    # Get settings, if any
     if widget_instance.settings:
         settings = widget_instance.settings
     else:
         settings = {}
+    # Get widget
     try:
-        context = widget.get_context_data(**settings)
-    except AttributeError:
+        widget = get_widget(widget_instance.widget_type)
+    except MissingWidgetType:
+        template_name = 'dashboard/widget-error.html'
         context = {}
-    try:
-        template_name = widget.template_name
-    except AttributeError:
-        template_name = 'dashboard/widget-missing-template.html'
+        context['error'] = _('Unknown widget type %(widget_type)s') % {
+            'widget_type': widget_instance.widget_type
+        }
         context['empty_type'] = widget_instance.widget_type
+    if widget:
+        # Get template
+        try:
+            template_name = widget.template_name
+        except AttributeError:
+            template_name = 'dashboard/widget-error.html'
+            context = {}
+            context['error'] = _('Missing template for %(widget_type)s') % {
+                'widget_type': widget_instance.widget_type
+            }
+            widget = None
+    if widget:
+        # Get context
+        try:
+            context = widget.get_context_data(**settings)
+        except:
+            logger.exception()
+            template_name = 'dashboard/widget-error.html'
+            context['error'] = _('Widget error. See error logs.')
+
     return render_to_string(template_name, context)

django/website/dashboard/views.py

@@ -3,7 +3,7 @@ from django.views.generic import TemplateView
 from hid.assets import require_assets
 
 from dashboard.models import Dashboard
-from dashboard.widget_pool import get_widget
+from dashboard.widget_pool import get_widget, MissingWidgetType
 
 
 class DashboardView(TemplateView):
@@ -43,7 +43,10 @@ class DashboardView(TemplateView):
         # Ensure we have all the javascript & css dependencies
         require_assets('dashboard/dashboard.css')
         for widget in widgets:
-            widget_type = get_widget(widget.widget_type)
+            try:
+                widget_type = get_widget(widget.widget_type)
+            except MissingWidgetType:
+                continue
             if hasattr(widget_type, 'javascript'):
                 require_assets(*widget_type.javascript)
             if hasattr(widget_type, 'css'):

django/website/dashboard/widget_pool.py

 _pool = {}
 
 
+class MissingWidgetType(Exception):
+    """ Exception raised when a widget type is missing """
+    pass
+
+
 def register_widget(name, widget):
     """ Register a new widget type
 
@@ -24,10 +29,13 @@ def get_widget(name):
     Returns:
         The widget object as registered with register_widget
     Raises:
-        KeyError: If the widget type does not exist
+        MissingWidgetType: If the widget type does not exist
     """
     global _pool
-    return _pool[name]
+    try:
+        return _pool[name]
+    except KeyError:
+        raise MissingWidgetType()
 
 
 class BasicTextWidget(object):