fix visible true|false toggle for pie traces

- probably a side-effect from a splom-perf PR

Author: etpinard

src/traces/pie/base_plot.js

@@ -16,8 +16,7 @@ exports.name = 'pie';
 exports.plot = function(gd) {
     var Pie = Registry.getModule('pie');
     var cdPie = getModuleCalcData(gd.calcdata, Pie)[0];
-
-    if(cdPie.length) Pie.plot(gd, cdPie);
+    Pie.plot(gd, cdPie);
 };
 
 exports.clean = function(newFullData, newFullLayout, oldFullData, oldFullLayout) {

test/jasmine/tests/pie_test.js

@@ -818,6 +818,26 @@ describe('Pie traces', function() {
         .catch(failTest)
         .then(done);
     });
+
+    it('should be able to toggle visibility', function(done) {
+        var mock = Lib.extendDeep({}, require('@mocks/pie_title_multiple.json'));
+
+        function _assert(msg, exp) {
+            return function() {
+                var layer = d3.select(gd).select('.pielayer');
+                expect(layer.selectAll('.trace').size()).toBe(exp, msg);
+            };
+        }
+
+        Plotly.plot(gd, mock)
+        .then(_assert('base', 4))
+        .then(function() { return Plotly.restyle(gd, 'visible', false); })
+        .then(_assert('both visible:false', 0))
+        .then(function() { return Plotly.restyle(gd, 'visible', true); })
+        .then(_assert('back to visible:true', 4))
+        .catch(failTest)
+        .then(done);
+    });
 });
 
 describe('pie hovering', function() {