added PreventUpdate exception and attached handler to Flask server

plotly · Jan 19, 2018 · ad92fa3 · ad92fa3
1 parent 3085796
commit ad92fa3
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Showing 2 changed files with 10 additions and 0 deletions.
diff --git a/dash/dash.py b/dash/dash.py
@@ -1,3 +1,4 @@
+import sys
 import collections
 import importlib
 import json
@@ -53,6 +54,12 @@ def __init__(
         # gzip
         Compress(self.server)
 
+        @self.server.errorhandler(exceptions.PreventUpdate)
+        def handle_error(error):
+            """Handle a halted callback and return an empty 204 response"""
+            print(error, file=sys.stderr)
+            return ('', 204)
+
         # static files from the packages
         self.css = Css()
         self.scripts = Scripts()

diff --git a/dash/exceptions.py b/dash/exceptions.py
@@ -40,3 +40,6 @@ class IDsCantContainPeriods(CallbackException):
 
 class CantHaveMultipleOutputs(CallbackException):
     pass
+
+class PreventUpdate(CallbackException):
+    pass