guard against infinite loops

... in scattergl positions cleanup.

Author: etpinard

src/traces/scattergl/index.js

@@ -399,11 +399,11 @@ function plot(gd, subplot, cdata) {
                     var srcPos = lineOptions.positions;
 
                     var firstptdef = 0;
-                    while(isNaN(srcPos[firstptdef]) || isNaN(srcPos[firstptdef + 1])) {
+                    while(firstptdef < srcPos.length && (isNaN(srcPos[firstptdef]) || isNaN(srcPos[firstptdef + 1]))) {
                         firstptdef += 2;
                     }
                     var lastptdef = srcPos.length - 2;
-                    while(isNaN(srcPos[lastptdef]) || isNaN(srcPos[lastptdef + 1])) {
+                    while(lastptdef > -1 && (isNaN(srcPos[lastptdef]) || isNaN(srcPos[lastptdef + 1]))) {
                         lastptdef -= 2;
                     }
                     pos = pos.concat(srcPos.slice(firstptdef, lastptdef + 2));
@@ -443,12 +443,12 @@ function plot(gd, subplot, cdata) {
                 var firstptdef, lastptdef;
 
                 if(trace.fill === 'tozeroy') {
-                    while(isNaN(srcPos[firstpdef + 1])) {
                     firstptdef = 0;
+                    while(firstptdef < srcPos.length && isNaN(srcPos[firstptdef + 1])) {
                         firstptdef += 2;
                     }
-                    while(isNaN(srcPos[lastpdef + 1])) {
                     lastptdef = srcPos.length - 2;
+                    while(lastptdef > -1 && isNaN(srcPos[lastptdef + 1])) {
                         lastptdef -= 2;
                     }
                     if(srcPos[firstptdef + 1] !== 0) {
@@ -460,12 +460,12 @@ function plot(gd, subplot, cdata) {
                     }
                 }
                 else if(trace.fill === 'tozerox') {
-                    while(isNaN(srcPos[firstptdef])) {
                     firstptdef = 0;
+                    while(firstptdef < srcPos.length && isNaN(srcPos[firstptdef])) {
                         firstptdef += 2;
                     }
-                    while(isNaN(srcPos[lastptdef])) {
                     lastptdef = srcPos.length - 2;
+                    while(lastptdef > -1 && isNaN(srcPos[lastptdef])) {
                         lastptdef -= 2;
                     }
                     if(srcPos[firstptdef] !== 0) {

test/jasmine/tests/gl2d_plot_interact_test.js

@@ -1186,6 +1186,79 @@ describe('Test gl2d plots', function() {
         .catch(failTest)
         .then(done);
     });
+
+    it('@gl should not cause infinite loops when coordinate arrays start/end with NaN', function(done) {
+        function _assertPositions(msg, cont, exp) {
+            var pos = gd._fullLayout._plots.xy._scene[cont]
+                .map(function(opt) { return opt.positions; });
+            expect(pos).toBeCloseTo2DArray(exp, 2, msg);
+        }
+
+        Plotly.plot(gd, [{
+            type: 'scattergl',
+            mode: 'lines',
+            x: [1, 2, 3],
+            y: [null, null, null]
+        }, {
+            type: 'scattergl',
+            mode: 'lines',
+            x: [1, 2, 3],
+            y: [1, 2, null]
+        }, {
+            type: 'scattergl',
+            mode: 'lines',
+            x: [null, 2, 3],
+            y: [1, 2, 3]
+        }, {
+            type: 'scattergl',
+            mode: 'lines',
+            x: [null, null, null],
+            y: [1, 2, 3]
+        }, {
+        }])
+        .then(function() {
+            _assertPositions('base', 'lineOptions', [
+                [],
+                [1, 1, 2, 2],
+                [2, 2, 3, 3],
+                []
+            ]);
+
+            return Plotly.restyle(gd, 'fill', 'tozerox');
+        })
+        .then(function() {
+            _assertPositions('tozerox', 'lineOptions', [
+                [],
+                [1, 1, 2, 2],
+                [2, 2, 3, 3],
+                []
+            ]);
+            _assertPositions('tozerox', 'fillOptions', [
+                [0, undefined, 0, undefined],
+                [0, 1, 1, 1, 2, 2, 0, 2],
+                [0, 2, 2, 2, 3, 3, 0, 3],
+                [0, undefined, 0, undefined]
+            ]);
+
+            return Plotly.restyle(gd, 'fill', 'tozeroy');
+        })
+        .then(function() {
+            _assertPositions('tozeroy', 'lineOptions', [
+                [],
+                [1, 1, 2, 2],
+                [2, 2, 3, 3],
+                []
+            ]);
+            _assertPositions('tozeroy', 'fillOptions', [
+                [undefined, 0, undefined, 0],
+                [1, 0, 1, 1, 2, 2, 2, 0],
+                [2, 0, 2, 2, 3, 3, 3, 0],
+                [undefined, 0, undefined, 0]
+            ]);
+        })
+        .catch(failTest)
+        .then(done);
+    });
 });
 
 describe('Test scattergl autorange:', function() {