add gl2d replot-from-blank-graph test case

Author: etpinard

test/jasmine/tests/gl_plot_interact_test.js

@@ -580,4 +580,41 @@ describe('Test gl plot side effects', function() {
             });
         });
     });
+
+    it('should be able to replot from a blank graph', function(done) {
+        var gd = createGraphDiv();
+
+        function assert(cnt) {
+            var nodes = d3.selectAll('canvas');
+            expect(nodes.size()).toEqual(cnt);
+        }
+
+        var data = [{
+            type: 'scattergl',
+            x: [1, 2, 3],
+            y: [2, 1, 2]
+        }];
+
+        Plotly.plot(gd, []).then(function() {
+            assert(0);
+
+            return Plotly.plot(gd, data);
+        }).then(function() {
+            assert(1);
+
+            return Plotly.purge(gd);
+        }).then(function() {
+            assert(0);
+
+            return Plotly.plot(gd, data);
+        }).then(function() {
+            assert(1);
+
+            return Plotly.deleteTraces(gd, [0]);
+        }).then(function() {
+            assert(0);
+
+            return Plotly.purge(gd);
+        }).then(done);
+    });
 });