fix #3961 - fill in zLabel during choropleth hover

... so that hover templates with `%{z}` can render the z value
    using the same formatting as by default.

Author: etpinard

src/components/fx/hover.js

@@ -896,11 +896,15 @@ function createHoverText(hoverData, opts, gd) {
         if(d.zLabel !== undefined) {
             if(d.xLabel !== undefined) text += 'x: ' + d.xLabel + '<br>';
             if(d.yLabel !== undefined) text += 'y: ' + d.yLabel + '<br>';
-            text += (text ? 'z: ' : '') + d.zLabel;
+            if(d.trace.type !== 'choropleth') {
+                text += (text ? 'z: ' : '') + d.zLabel;
+            }
         } else if(showCommonLabel && d[hovermode + 'Label'] === t0) {
             text = d[(hovermode === 'x' ? 'y' : 'x') + 'Label'] || '';
         } else if(d.xLabel === undefined) {
-            if(d.yLabel !== undefined && d.trace.type !== 'scattercarpet') text = d.yLabel;
+            if(d.yLabel !== undefined && d.trace.type !== 'scattercarpet') {
+                text = d.yLabel;
+            }
         } else if(d.yLabel === undefined) text = d.xLabel;
         else text = '(' + d.xLabel + ', ' + d.yLabel + ')';
 

src/traces/choropleth/hover.js

@@ -6,7 +6,6 @@
 * LICENSE file in the root directory of this source tree.
 */
 
-
 'use strict';
 
 var Axes = require('../../plots/cartesian/axes');
@@ -47,17 +46,16 @@ module.exports = function hoverPoints(pointData, xval, yval) {
     pointData.index = pt.index;
     pointData.location = pt.loc;
     pointData.z = pt.z;
+    pointData.zLabel = Axes.tickText(geo.mockAxis, geo.mockAxis.c2l(pt.z), 'hover').text;
     pointData.hovertemplate = pt.hovertemplate;
 
     makeHoverInfo(pointData, trace, pt, geo.mockAxis);
 
     return [pointData];
 };
 
-function makeHoverInfo(pointData, trace, pt, axis) {
-    if(trace.hovertemplate) {
-        return;
-    }
+function makeHoverInfo(pointData, trace, pt) {
+    if(trace.hovertemplate) return;
 
     var hoverinfo = pt.hi || trace.hoverinfo;
 
@@ -73,18 +71,16 @@ function makeHoverInfo(pointData, trace, pt, axis) {
 
     var text = [];
 
-    function formatter(val) {
-        return Axes.tickText(axis, axis.c2l(val), 'hover').text;
-    }
-
     if(hasIdAsNameLabel) {
         pointData.nameOverride = pt.loc;
     } else {
         if(hasName) pointData.nameOverride = trace.name;
         if(hasLocation) text.push(pt.loc);
     }
 
-    if(hasZ) text.push(formatter(pt.z));
+    if(hasZ) {
+        text.push(pointData.zLabel);
+    }
     if(hasText) {
         fillText(pt, trace, text);
     }

test/jasmine/tests/choropleth_test.js

@@ -200,6 +200,31 @@ describe('Test choropleth hover:', function() {
         )
         .then(done);
     });
+
+    describe('should preserve z formatting hovetemplate equivalence', function() {
+        var base = function() {
+            return {
+                data: [{
+                    type: 'choropleth',
+                    locations: ['RUS'],
+                    z: [10.02132132143214321]
+                }]
+            };
+        };
+
+        var pos = [400, 160];
+        var exp = ['10.02132', 'RUS'];
+
+        it('- base case (truncate z decimals)', function(done) {
+            run(pos, base(), exp).then(done);
+        });
+
+        it('- hovertemplate case (same z truncation)', function(done) {
+            var fig = base();
+            fig.hovertemplate = '%{z}<extra>%{location}</extra>';
+            run(pos, fig, exp).then(done);
+        });
+    });
 });
 
 describe('choropleth drawing', function() {