fix 3784 waterfall connector line color coerce and default

Author: archmoj

Diff for: src/traces/waterfall/attributes.js

@@ -11,6 +11,7 @@
 var barAttrs = require('../bar/attributes');
 var lineAttrs = require('../scatter/attributes').line;
 var extendFlat = require('../../lib/extend').extendFlat;
+var Color = require('../../components/color');
 
 function directionAttrs(dirTxt) {
     return {
@@ -94,7 +95,7 @@ module.exports = {
 
     connector: {
         line: {
-            color: lineAttrs.color,
+            color: extendFlat({}, lineAttrs.color, {dflt: Color.defaultLine}),
             width: lineAttrs.width,
             dash: lineAttrs.dash,
             editType: 'plot'

Diff for: test/image/baselines/waterfall-grouping-vs-defaults.png

@@ -202,6 +202,15 @@ describe('Waterfall.supplyDefaults', function() {
         expect(traceOut.xcalendar).toBe('coptic');
         expect(traceOut.ycalendar).toBe('ethiopian');
     });
+
+    it('should coerce connector line color and default to Color.defaultLine', function() {
+        traceIn = {
+            x: [1, 2, 3],
+            y: [1, 2, 3],
+        };
+        supplyDefaults(traceIn, traceOut, defaultColor, {});
+        expect(traceOut.connector.line.color).toBe(color.defaultLine);
+    });
 });
 
 describe('waterfall calc / crossTraceCalc', function() {