autoSpec should never return undefined for {color: {color}}

[tophtucker]

Noticed while working on #1385 — this is, I think, the last undefined that autoSpec is returning:

plot/src/marks/auto.js

Lines 195 to 199 in 02731fb

	color: {
	value: colorValue ?? null,
	reduce: colorReduce ?? null,
	...(colorColor !== undefined && {color: colorColor})
	},

[mbostock]

I’m not following this comment. It looks to me that the code can never return color: {color: undefined} because of the colorColor !== undefined check? So the type is

type AutoColorMaterializedOptions =
  | {value: ChannelValue | null; reduce: ChannelReduce | null}
  | {value: null; reduce: null; color: string};

which seems correct to me. We don’t want to say color: null when there’s a value or reduce because that would mean setting a constant color of none.

[tophtucker]

Oh! Sorry, I filed this hastily; I meant that the color property might not be in the returned object, not that it might be present and undefined (color?: string, not color: string | undefined). If that union type seems fine to you, then it’s fine with me. It felt weird that we’re not returning a fixed shape, but I hadn’t thought through what setting color: null would actually do, so, forget it! 😅