fix hovertemplate fallback when hovering on scatter fills

Author: etpinard

src/components/fx/hover.js

@@ -672,11 +672,15 @@ function _hover(gd, evt, subplot, noHoverEvent) {
         var pt = hoverData[itemnum];
         var eventData = helpers.makeEventData(pt, pt.trace, pt.cd);
 
-        var ht = false;
-        if(pt.cd[pt.index] && pt.cd[pt.index].ht) ht = pt.cd[pt.index].ht;
-        hoverData[itemnum].hovertemplate = ht || pt.trace.hovertemplate || false;
-        hoverData[itemnum].eventData = [eventData];
+        if(pt.hovertemplate !== false) {
+            var ht = false;
+            if(pt.cd[pt.index] && pt.cd[pt.index].ht) {
+                ht = pt.cd[pt.index].ht;
+            }
+            pt.hovertemplate = ht || pt.trace.hovertemplate || false;
+        }
 
+        pt.eventData = [eventData];
         newhoverdata.push(eventData);
     }
 

src/traces/scatter/hover.js

@@ -179,7 +179,7 @@ module.exports = function hoverPoints(pointData, xval, yval, hovermode) {
                 y0: yAvg,
                 y1: yAvg,
                 color: color,
-                hovertemplate: '%{name}'
+                hovertemplate: false
             });
 
             delete pointData.index;

test/jasmine/tests/hover_label_test.js

@@ -1938,6 +1938,38 @@ describe('hover info', function() {
         .catch(failTest)
         .then(done);
     });
+
+    it('should fallback to regular hover content when hoveron does not support hovertemplate', function(done) {
+        var gd = createGraphDiv();
+        var fig = Lib.extendDeep({}, require('@mocks/scatter_fill_self_next.json'));
+
+        fig.data.forEach(function(trace) {
+            trace.hoveron = 'points+fills';
+            trace.hovertemplate = '%{x} | %{y}';
+        });
+
+        fig.layout.hovermode = 'closest';
+        fig.layout.showlegend = false;
+        fig.layout.margin = {t: 0, b: 0, l: 0, r: 0};
+
+        Plotly.plot(gd, fig)
+        .then(function() { _hoverNatural(gd, 180, 200); })
+        .then(function() {
+            assertHoverLabelContent({
+                nums: 'trace 1',
+                name: ''
+            }, 'hovering on a fill');
+        })
+        .then(function() { _hoverNatural(gd, 50, 95); })
+        .then(function() {
+            assertHoverLabelContent({
+                nums: '0 | 5',
+                name: 'trace 1'
+            }, 'hovering on a pt');
+        })
+        .catch(failTest)
+        .then(done);
+    });
 });
 
 describe('hover info on stacked subplots', function() {