fix choropleth hover for countries w/ have polygons that cross -180

- these countries are Russia and Fiji.
- Note that other countries have polygons on either side of
  the antimeridian (e.g. some Aleutian island for the USA),
  but those don't confuse the 'contains' method.

Author: etpinard

src/traces/choropleth/hover.js

@@ -28,6 +28,10 @@ module.exports = function hoverPoints(pointData, xval, yval) {
                 if(pt._polygons[j].contains([xval, yval])) {
                     isInside = !isInside;
                 }
+                // for polygons that cross antimeridian as xval is in [-180, 180]
+                if(pt._polygons[j].contains([xval + 360, yval])) {
+                    isInside = !isInside;
+                }
             }
 
             if(isInside) break;

src/traces/choropleth/plot.js

@@ -55,7 +55,7 @@ function calcGeoJSON(calcTrace, topojson) {
     var trace = calcTrace[0].trace;
     var len = calcTrace.length;
     var features = getTopojsonFeatures(trace, topojson);
-    var i, j, k;
+    var i, j, k, m;
 
     for(i = 0; i < len; i++) {
         var calcPt = calcTrace[i];
@@ -74,6 +74,25 @@ function calcGeoJSON(calcTrace, topojson) {
         var coords = geometry.coordinates;
         calcPt._polygons = [];
 
+        // Russia and Fiji have landmasses that cross the antimeridian,
+        // we need to add +360 to their longitude coordinates, so that
+        // polygon 'contains' doesn't get confused when crossing the antimeridian.
+        //
+        // Note that other countries have polygons on either side of the antimeridian
+        // (e.g. some Aleutian island for the USA), but those don't confuse
+        // the 'contains' method; these are skipped here.
+        if(calcPt.loc === 'RUS' || calcPt.loc === 'FJI') {
+            for(j = 0; j < coords.length; j++) {
+                for(k = 0; k < coords[j].length; k++) {
+                    for(m = 0; m < coords[j][k].length; m++) {
+                        if(coords[j][k][m][0] < 0) {
+                            coords[j][k][m][0] += 360;
+                        }
+                    }
+                }
+            }
+        }
+
         switch(geometry.type) {
             case 'MultiPolygon':
                 for(j = 0; j < coords.length; j++) {

test/jasmine/tests/geo_test.js

@@ -1290,6 +1290,46 @@ describe('Test geo interactions', function() {
         .catch(fail)
         .then(done);
     });
+
+    it('should get hover right for choropleths involving landmasses that cross antimeridian', function(done) {
+        var gd = createGraphDiv();
+
+        function check(lonlat, hoverLabelCnt, msg) {
+            var projection = gd._fullLayout.geo._subplot.projection;
+            var px = projection(lonlat);
+
+            mouseEvent('mousemove', px[0], px[1]);
+            expect(d3.selectAll('g.hovertext').size()).toBe(hoverLabelCnt, msg);
+
+            delete gd._lastHoverTime;
+        }
+
+        Plotly.newPlot(gd, [{
+            type: 'choropleth',
+            locations: ['RUS', 'FJI'],
+            z: [0, 1]
+        }])
+        .then(function() {
+            check([81, 66], 1, 'spot in north-central Russia that polygon.contains gets wrong before +360 shift');
+            check([-80, 66], 0, 'spot north of Hudson bay that polygon.contains believe is in Russia before before +360 shift');
+
+            return Plotly.relayout(gd, 'geo.projection.rotation.lon', 180);
+        })
+        .then(function() {
+            check([-174, 65], 1, 'spot in Russia mainland beyond antimeridian');
+
+            return Plotly.relayout(gd, {
+                'geo.center.lat': -16,
+                'geo.projection.scale': 17
+            });
+        })
+        .then(function() {
+            check([179, -16.6], 1, 'spot on Fiji island that cross antimeridian west of antimeridian');
+            check([-179.9, -16.2], 1, 'spot on Fiji island that cross antimeridian east of antimeridian');
+        })
+        .catch(fail)
+        .then(done);
+    });
 });
 
 describe('Test event property of interactions on a geo plot:', function() {