mutate uid of expanded traces w.r.t to expanded index:

- so that the 'same' expanded trace keep the same uid
  on update.

Author: etpinard

src/plots/plots.js

@@ -657,6 +657,10 @@ plots.supplyDataDefaults = function(dataIn, dataOut, layout) {
                 var expandedTrace = expandedTraces[j],
                     fullExpandedTrace = plots.supplyTraceDefaults(expandedTrace, cnt, layout);
 
+                // mutate uid w.r.t to expanded index to promote consistency
+                // between update calls.
+                expandedTrace.uid = fullExpandedTrace.uid = fullTrace.uid + '-' + j;
+
                 // add info about parent data trace
                 fullExpandedTrace.index = i;
                 fullExpandedTrace._input = trace;

test/jasmine/tests/transforms_test.js

@@ -113,9 +113,12 @@ describe('one-to-one transforms:', function() {
     it('Plotly.plot should plot the transform trace', function(done) {
         var data = Lib.extendDeep([], mockData0);
 
-        Plotly.plot(createGraphDiv(), data).then(function() {
+        Plotly.plot(createGraphDiv(), data).then(function(gd) {
             assertDims([3]);
 
+            var uid = data[0].uid;
+            expect(gd._fullData[0].uid).toEqual(uid + '-0');
+
             done();
         });
     });