Allow specifying labels in time scale options

[kurkle]

Currently time scale only reads labels from data.labels.
If both axes are time scales, this is not sufficient.

So this PR allows specifying labels under scale options also.

[benmccann]

@kurkle this only updates the docs, but from the PR description I would expect code to have changed as well. Did you accidentally leave some changes off of the PR?

[kurkle]

@kurkle this only updates the docs, but from the PR description I would expect code to have changed as well. Did you accidentally leave some changes off of the PR?

Its so small change, you missed it. Had any ☕️ yet 😄

[benmccann]

Haha. Sorry

This change looks fine to me, but I'm curious why ticks.source: 'data' wouldn't allow you to accomplish the same thing?

The other thing I wonder is if any other scales would need this same functionality

[etimberg]

I wonder if we can extend the same pattern to the category scale and close out #3193 too

[kurkle]

I wonder if we can extend the same pattern to the category scale and close out #3193 too

category scale already supports this, and additionally xLabes/yLabels:

Chart.js/src/scales/scale.category.js

Lines 15 to 18 in 2a96d83

	getLabels: function() {
	var data = this.chart.data;
	return this.options.labels || (this.isHorizontal() ? data.xLabels : data.yLabels) || data.labels;
	},

Not quite sure how this would solve #3193?

[kurkle]

I'm curious why ticks.source: 'data' wouldn't allow you to accomplish the same thing?

Can't find the chart right now , but for example if there is no data for all desired labels.

[nagix]

@kurkle You might want to update the time scale document?

[simonbrunel]

Looks good! I'm curious why linear scales don't need any change to support labels in the scale options?

[kurkle]

Looks good! I'm curious why linear scales don't need any change to support labels in the scale options?

linear scales just don't support labels in any way (yet). I'd leave that for another PR.

[simonbrunel]

I thought linear scales was using labels to determine the position the x position of each data:

data: {
    labels: [0, 2, 6, 8],
    datasets: [{
        data: [1, 4, 8, 2]
    }]
}

// e.q.
data: [
    {x: 0, y: 1},
    {x: 2, y: 4},
    {x: 6, y: 8},
    {x: 8, y: 2}
]

[kurkle]

@simonbrunel It does not work: Pen
'line' chart type defaults to category as x-axis, could that be why you thought linear scales support labels?.

Chart.js/src/controllers/controller.line.js

Lines 21 to 23 in e5c68e2

	xAxes: [{
	type: 'category',
	id: 'x-axis-0'

[simonbrunel]

@kurkle can we also add unit tests?