Merge pull request #5067 from minrk/widget-error

show traceback in widget handlers

IPython/html/widgets/interaction.py

@@ -20,6 +20,7 b' except ImportError:'
     from IPython.utils.signatures import signature, Parameter
 from inspect import getcallargs
 
+from IPython.core.getipython import get_ipython
 from IPython.html.widgets import (Widget, TextWidget,
     FloatSliderWidget, IntSliderWidget, CheckboxWidget, DropdownWidget,
     ContainerWidget, DOMWidget)
@@ -205,7 +206,14 b' def interactive(__interact_f, **kwargs):'
             container.kwargs[widget.description] = value
         if co:
             clear_output(wait=True)
-        container.result = f(**container.kwargs)
+        try:
+            container.result = f(**container.kwargs)
+        except Exception as e:
+            ip = get_ipython()
+            if ip is None:
+                container.log.warn("Exception in interact callback: %s", e, exc_info=True)
+            else:
+                ip.showtraceback()
 
     # Wire up the widgets
     for widget in kwargs_widgets:

IPython/html/widgets/widget.py

@@ -14,6 +14,7 b' in the IPython notebook front-end.'
 #-----------------------------------------------------------------------------
 from contextlib import contextmanager
 
+from IPython.core.getipython import get_ipython
 from IPython.kernel.comm import Comm
 from IPython.config import LoggingConfigurable
 from IPython.utils.traitlets import Unicode, Dict, Instance, Bool, List, Tuple
@@ -33,7 +34,11 b' class CallbackDispatcher(LoggingConfigurable):'
             try:
                 local_value = callback(*args, **kwargs)
             except Exception as e:
-                self.log.warn("Exception in callback %s: %s", callback, e)
+                ip = get_ipython()
+                if ip is None:
+                    self.log.warn("Exception in callback %s: %s", callback, e, exc_info=True)
+                else:
+                    ip.showtraceback()
             else:
                 value = local_value if local_value is not None else value
         return value
@@ -54,6 +59,18 b' class CallbackDispatcher(LoggingConfigurable):'
         elif not remove and callback not in self.callbacks:
             self.callbacks.append(callback)
 
+def _show_traceback(method):
+    """decorator for showing tracebacks in IPython"""
+    def m(self, *args, **kwargs):
+        try:
+            return(method(self, *args, **kwargs))
+        except Exception as e:
+            ip = get_ipython()
+            if ip is None:
+                self.log.warn("Exception in widget method %s: %s", method, e, exc_info=True)
+            else:
+                ip.showtraceback()
+    return m
 
 class Widget(LoggingConfigurable):
     #-------------------------------------------------------------------------
@@ -241,6 +258,7 b' class Widget(LoggingConfigurable):'
         value != self._property_lock[1]
     
     # Event handlers
+    @_show_traceback
     def _handle_msg(self, msg):
         """Called when a msg is received from the front-end"""
         data = msg['content']['data']