Background Color scriptable option and legend item color is black

[stockiNail]

Expected Behavior

I used the Chart.js sample of Doughnut and I used Patternomaly to create canvas pattern. This is what I'm expecting:

This is the code of scriptable options :

backgroundColor: function(context) {
	var index = context.dataIndex;
	if (index === 0){
		return pattern.draw('square', '#ff6384');
	}
	if (index === 1){
		return pattern.draw('circle', '#36a2eb');
	}
	if (index === 2){
		return pattern.draw('diamond', '#cc65fe');
	}
	if (index === 3){
		return pattern.draw('triangle', '#ffce56');
	}
	return pattern.draw('zigzag', '#fcc465');
},

Current Behavior

Using scriptable options, the result is the legend item color is black.

If, instead of using scriptable options, I'm passing the array of pattern, it works.

backgroundColor: [
	pattern.draw('square', '#ff6384'),
	pattern.draw('circle', '#36a2eb'),
	pattern.draw('diamond', '#cc65fe'),
	pattern.draw('triangle', '#ffce56'),
	pattern.draw('zigzag', '#fcc465')
],

I've tested also my canvas pattern (not by Patternomaly) and the result is the same.

Environment

• Chart.js version: 2.8.0
• Browser name and version: FF 65.0.2

[etimberg]

I think this is due to #2281. The code for the legend items is

Chart.js/src/plugins/plugin.legend.js

Lines 49 to 67 in 75e76cf

	generateLabels: function(chart) {
	var data = chart.data;
	return helpers.isArray(data.datasets) ? data.datasets.map(function(dataset, i) {
	return {
	text: dataset.label,
	fillStyle: (!helpers.isArray(dataset.backgroundColor) ? dataset.backgroundColor : dataset.backgroundColor[0]),
	hidden: !chart.isDatasetVisible(i),
	lineCap: dataset.borderCapStyle,
	lineDash: dataset.borderDash,
	lineDashOffset: dataset.borderDashOffset,
	lineJoin: dataset.borderJoinStyle,
	lineWidth: dataset.borderWidth,
	strokeStyle: dataset.borderColor,
	pointStyle: dataset.pointStyle,
	// Below is extra data used for toggling the datasets
	datasetIndex: i
	};
	}, this) : [];

which doesn't properly resolve scriptable options

[nagix]

#5621 addresses the issue in the legend with scriptable options.