enable unified hovermode via template

Author: archmoj

src/plots/cartesian/layout_defaults.js

@@ -249,8 +249,9 @@ module.exports = function supplyLayoutDefaults(layoutIn, layoutOut, fullData) {
         handleTypeDefaults(axLayoutIn, axLayoutOut, coerce, defaultOptions);
         handleAxisDefaults(axLayoutIn, axLayoutOut, coerce, defaultOptions, layoutOut);
 
-        var unifiedHover = layoutIn.hovermode && ['x unified', 'y unified'].indexOf(layoutIn.hovermode) !== -1;
-        var unifiedSpike = unifiedHover && axLetter === layoutIn.hovermode.charAt(0);
+        var hovermode = layoutOut.hovermode || layoutIn.hovermode;
+        var unifiedHover = hovermode && ['x unified', 'y unified'].indexOf(hovermode) !== -1;
+        var unifiedSpike = unifiedHover && axLetter === hovermode.charAt(0);
         var spikecolor = coerce2('spikecolor', unifiedHover ? axLayoutOut.color : undefined);
         var spikethickness = coerce2('spikethickness', unifiedHover ? 1.5 : undefined);
         var spikedash = coerce2('spikedash', unifiedHover ? 'dot' : undefined);

test/jasmine/tests/hover_label_test.js

@@ -4093,6 +4093,24 @@ describe('hovermode: (x|y)unified', function() {
             .then(done);
     });
 
+    it('unified hover modes should work for x/y cartesian traces via template', function(done) {
+        var mockCopy = Lib.extendDeep({}, mock);
+        delete mockCopy.layout.hovermode;
+        mockCopy.layout.template = {
+            layout: {
+                hovermode: 'y unified'
+            }
+        };
+        Plotly.newPlot(gd, mockCopy)
+            .then(function(gd) {
+                _hover(gd, { yval: 6 });
+
+                assertLabel({title: '6', items: ['trace 0 : 2', 'trace 1 : 5']});
+            })
+            .catch(failTest)
+            .then(done);
+    });
+
     it('x unified should work for x/y cartesian traces with legendgroup', function(done) {
         var mockLegendGroup = require('@mocks/legendgroup.json');
         var mockCopy = Lib.extendDeep({}, mockLegendGroup);