From d260d0deb240f585eb0e9c0212c4c60f781d549e Mon Sep 17 00:00:00 2001
From: Philippe Duval <philippe@plot.ly>
Date: Tue, 18 Sep 2018 11:54:04 -0400
Subject: [PATCH 1/2] Add InvalidResourceError exception type, fix #393.

---
 dash/dash.py       | 11 +++++++++--
 dash/exceptions.py |  4 ++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/dash/dash.py b/dash/dash.py
index ec15aada7b..95924d2242 100644
--- a/dash/dash.py
+++ b/dash/dash.py
@@ -222,6 +222,10 @@ def add_url(name, view_func, methods=('GET',)):
         self._cached_layout = None
         self.routes = []
 
+        # add a handler for components suites errors to return 404
+        self.server.errorhandler(exceptions.InvalidResourceError)(
+            self._invalid_resources_handler)
+
     @property
     def layout(self):
         return self._layout
@@ -411,14 +415,14 @@ def _generate_meta_html(self):
     # Serve the JS bundles for each package
     def serve_component_suites(self, package_name, path_in_package_dist):
         if package_name not in self.registered_paths:
-            raise Exception(
+            raise exceptions.InvalidResourceError(
                 'Error loading dependency.\n'
                 '"{}" is not a registered library.\n'
                 'Registered libraries are: {}'
                 .format(package_name, list(self.registered_paths.keys())))
 
         elif path_in_package_dist not in self.registered_paths[package_name]:
-            raise Exception(
+            raise exceptions.InvalidResourceError(
                 '"{}" is registered but the path requested is not valid.\n'
                 'The path requested: "{}"\n'
                 'List of registered paths: {}'
@@ -962,6 +966,9 @@ def add_resource(p, filepath):
                 elif f == 'favicon.ico':
                     self._favicon = path
 
+    def _invalid_resources_handler(self, err):
+        return err.args[0], 404
+
     def get_asset_url(self, path):
         asset = _get_asset_path(
             self.config.requests_pathname_prefix,
diff --git a/dash/exceptions.py b/dash/exceptions.py
index 9cbb4e4dd9..5ec2779afb 100644
--- a/dash/exceptions.py
+++ b/dash/exceptions.py
@@ -60,3 +60,7 @@ class InvalidCallbackReturnValue(CallbackException):
 
 class InvalidConfig(DashException):
     pass
+
+
+class InvalidResourceError(DashException):
+    pass

From 12dadc17cb866ae1340616b690170b9c191f350d Mon Sep 17 00:00:00 2001
From: Philippe Duval <philippe@plot.ly>
Date: Wed, 19 Sep 2018 10:40:55 -0400
Subject: [PATCH 2/2] Update changelogs.

---
 CHANGELOG.md | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 749f132b1e..68e6c0c493 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,9 @@
-## 0.26.6 - 2018-09-18
+## 0.26.6 - 2018-09-19
 ## Fixed
-- Added `Cache-Control` headers to files served by `Dash.serve_components_suites`. [#387](https://github.com/plotly/dash/pull/387)
+- Added `Cache-Control` headers to files served by `Dash.serve_component_suites`. [#387](https://github.com/plotly/dash/pull/387)
 - Added time modified query string to collected components suites resources.
+- Added `InvalidResourceError`. [#393](https://github.com/plotly/dash/pull/393)
+- Added a flask errorhandler to catch `InvalidResourceError` from `serve_component_suites` and return a 404.
 
 ## 0.26.5 - 2018-09-10
 ## Fixed