Rework JavaScript->Python traitlet message properties.

Setting to null on JS side was causing some dropped messages.
The goal is for all of the messages to arrive, but not remain in the traitlet
for embdedding.

Author: jonmmease

js/src/Figure.js

@@ -1027,7 +1027,6 @@ var FigureView = widgets.DOMWidgetView.extend({
 
         this.model.set("_js2py_restyle", restyleMsg);
         this.touch();
-        this.model.set("_js2py_restyle", null);
     },
 
     /**
@@ -1058,7 +1057,6 @@ var FigureView = widgets.DOMWidgetView.extend({
 
         this.model.set("_js2py_relayout", relayoutMsg);
         this.touch();
-        this.model.set("_js2py_relayout", null);
     },
 
     /**
@@ -1092,7 +1090,6 @@ var FigureView = widgets.DOMWidgetView.extend({
 
         this.model.set("_js2py_update", updateMsg);
         this.touch();
-        this.model.set("_js2py_update", null);
     },
 
     /**
@@ -1157,7 +1154,6 @@ var FigureView = widgets.DOMWidgetView.extend({
 
             this.model.set("_js2py_pointsCallback", pointsMsg);
             this.touch();
-            this.model.set("_js2py_pointsCallback", null);
         }
     },
 
@@ -1390,7 +1386,6 @@ var FigureView = widgets.DOMWidgetView.extend({
 
         this.model.set("_js2py_layoutDelta", layoutDeltaMsg);
         this.touch();
-        this.model.set("_js2py_layoutDelta", null);
     },
 
     /**
@@ -1422,7 +1417,6 @@ var FigureView = widgets.DOMWidgetView.extend({
         console.log(["traceDeltasMsg", traceDeltasMsg]);
         this.model.set("_js2py_traceDeltas", traceDeltasMsg);
         this.touch();
-        this.model.set("_js2py_traceDeltas", null);
     }
 });
 

plotly/basewidget.py

@@ -451,8 +451,8 @@ def _handler_js2py_traceDeltas(self, change):
         # Receive message
         # ---------------
         msg_data = change['new']
-        self._js2py_traceDeltas = None
         if not msg_data:
+            self._js2py_traceDeltas = None
             return
 
         trace_deltas = msg_data['trace_deltas']
@@ -504,6 +504,8 @@ def _handler_js2py_traceDeltas(self, change):
                 while self._waiting_edit_callbacks:
                     self._waiting_edit_callbacks.pop()()
 
+        self._js2py_traceDeltas = None
+
     @observe('_js2py_layoutDelta')
     def _handler_js2py_layoutDelta(self, change):
         """
@@ -513,8 +515,8 @@ def _handler_js2py_layoutDelta(self, change):
         # Receive message
         # ---------------
         msg_data = change['new']
-        self._js2py_layoutDelta = None
         if not msg_data:
+            self._js2py_layoutDelta = None
             return
 
         layout_delta = msg_data['layout_delta']
@@ -566,6 +568,8 @@ def _handler_js2py_layoutDelta(self, change):
                 while self._waiting_edit_callbacks:
                     self._waiting_edit_callbacks.pop()()
 
+        self._js2py_layoutDelta = None
+
     @observe('_js2py_restyle')
     def _handler_js2py_restyle(self, change):
         """
@@ -575,8 +579,9 @@ def _handler_js2py_restyle(self, change):
         # Receive message
         # ---------------
         restyle_msg = change['new']
-        self._js2py_restyle = None
+
         if not restyle_msg:
+            self._js2py_restyle = None
             return
 
         style_data = restyle_msg['style_data']
@@ -589,6 +594,8 @@ def _handler_js2py_restyle(self, change):
                             trace_indexes=style_traces,
                             source_view_id=source_view_id)
 
+        self._js2py_restyle = None
+
     @observe('_js2py_update')
     def _handler_js2py_update(self, change):
         """
@@ -598,8 +605,9 @@ def _handler_js2py_update(self, change):
         # Receive message
         # ---------------
         update_msg = change['new']
-        self._js2py_update = None
+
         if not update_msg:
+            self._js2py_update = None
             return
 
         style = update_msg['style_data']
@@ -613,6 +621,8 @@ def _handler_js2py_update(self, change):
                            trace_indexes=trace_indexes,
                            source_view_id=source_view_id)
 
+        self._js2py_update = None
+
     @observe('_js2py_relayout')
     def _handler_js2py_relayout(self, change):
         """
@@ -622,8 +632,9 @@ def _handler_js2py_relayout(self, change):
         # Receive message
         # ---------------
         relayout_msg = change['new']
-        self._js2py_relayout = None
+
         if not relayout_msg:
+            self._js2py_relayout = None
             return
 
         relayout_data = relayout_msg['relayout_data']
@@ -640,6 +651,8 @@ def _handler_js2py_relayout(self, change):
         self.plotly_relayout(relayout_data=relayout_data,
                              source_view_id=source_view_id)
 
+        self._js2py_relayout = None
+
     @observe('_js2py_pointsCallback')
     def _handler_js2py_pointsCallback(self, change):
         """
@@ -649,8 +662,9 @@ def _handler_js2py_pointsCallback(self, change):
         # Receive message
         # ---------------
         callback_data = change['new']
-        self._js2py_pointsCallback = None
+
         if not callback_data:
+            self._js2py_pointsCallback = None
             return
 
         # Get event type
@@ -718,6 +732,8 @@ def _handler_js2py_pointsCallback(self, change):
             elif event_type == 'plotly_selected':
                 trace._dispatch_on_selection(points, selector)
 
+        self._js2py_pointsCallback = None
+
     # Callbacks
     # ---------
     def on_edits_completed(self, fn):