[typings] Allow returning null from scriptable function

[ties-s]

Expected Behavior

Should allow returning null from scriptable property functions like in example https://www.chartjs.org/docs/latest/samples/advanced/linear-gradient.html

Current Behavior

Type error

Type '(context: ScriptableContext<"line">, options: AnyObject) => Color | null' is not assignable to type 'string | _DeepPartialObject<CanvasGradient> | _DeepPartialObject<CanvasPattern> | ((ctx: ScriptableContext<"line">, options: AnyObject) => Color) | undefined'

Possible Solution

Change the type to also allow null

Steps to Reproduce

https://www.typescriptlang.org/play?#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

Context

Trying to implement the mentioned example in a TypeScript environment

Environment

• Chart.js version: 3.5.1
• Browser name and version: n/a (typescript compiler)
• Link to your project:

[kurkle]

I think the sample is actually flawed, it should return undefined, which is allowed.

[ties-s]

Not really

Type 'undefined' is not assignable to type 'Color'.

[kurkle]

Not really

Type 'undefined' is not assignable to type 'Color'.

Ok, definitely a problem in the types.