Fix for number 0 treated as invalid in hover (#1)

* treat zero as valid fixes #2660

* PR suggestions: toBe instead of toEqual

Author: dalle

src/components/drawing/index.js

@@ -650,7 +650,7 @@ drawing.textPointStyle = function(s, trace, gd) {
         var p = d3.select(this);
         var text = Lib.extractOption(d, trace, 'tx', 'text');
 
-        if(!text) {
+        if(!text && text !== 0) {
             p.remove();
             return;
         }

src/components/fx/hover.js

@@ -842,7 +842,7 @@ function createHoverText(hoverData, opts, gd) {
         else if(d.yLabel === undefined) text = d.xLabel;
         else text = '(' + d.xLabel + ', ' + d.yLabel + ')';
 
-        if(d.text && !Array.isArray(d.text)) {
+        if((d.text || d.text === 0) && !Array.isArray(d.text)) {
             text += (text ? '<br>' : '') + d.text;
         }
 

test/jasmine/tests/hover_label_test.js

@@ -132,6 +132,46 @@ describe('hover info', function() {
         });
     });
 
+    describe('hover info text with 0', function() {
+        var mockCopy = Lib.extendDeep({}, mock);
+
+        mockCopy.data[0].text = [];
+        // we treat number 0 as valid text
+        // see https://github.com/plotly/plotly.js/issues/2660
+        mockCopy.data[0].text[17] = 0;
+        mockCopy.data[0].hoverinfo = 'text';
+        mockCopy.data[0].mode = 'lines+markers+text';
+
+        beforeEach(function(done) {
+            Plotly.plot(createGraphDiv(), mockCopy.data, mockCopy.layout).then(done);
+        });
+
+        it('responds to hover text', function() {
+            var gd = document.getElementById('graph');
+            Fx.hover('graph', evt, 'xy');
+
+            var hoverTrace = gd._hoverdata[0];
+
+            expect(hoverTrace.curveNumber).toBe(0);
+            expect(hoverTrace.pointNumber).toBe(17);
+            expect(hoverTrace.x).toBe(0.388);
+            expect(hoverTrace.y).toBe(1);
+            expect(hoverTrace.text).toBe(0);
+
+            var txs = d3.select(gd).selectAll('.textpoint text');
+
+            expect(txs.size()).toBe(1);
+
+            txs.each(function() {
+                expect(d3.select(this).text()).toBe('0');
+            });
+
+            assertHoverLabelContent({
+                nums: '0'
+            });
+        });
+    });
+
     describe('hover info all', function() {
         var mockCopy = Lib.extendDeep({}, mock);