array-type configuration differs from Visual Studio Code preview

[EdJoPaTo]

The preview in Visual Studio Code automatically uses readonly T[] over ReadonlyArray<T>.
When looking on Previews of functions and parameters I get familiar with this style of writing parameters. The current rules want me to write a different style.

I havnt looked into Visual Studio Codes Preview Logic or why they do it that way. I only want to start a discussion about it.

These two following methods are accepting the same parameter but the preview of these is the same. The first one produces this xo error:
Array type using T[] is forbidden for non-simple types. Use Array<T> instead. @typescript-eslint/array-type

export function foo(something: readonly Readonly<Something>[]): number {
  return something.length
}

export function bar(something: ReadonlyArray<Readonly<Something>>): number {
  return something.length
}

What are other opinions about changing the rule array-type towards simple arrays?

[sindresorhus]

I agree that the first one is nicer. The point of the rule was to prevent things like (string | boolean)[] in favor of Array<string | boolean>. Maybe the rule could be made better somehow?

[EdJoPaTo]

I tend towards using extra types if unions are more complex. string | boolean might still end up in brackets for me but as soon as there are three or one of them isn't a basic type anymore the union will get its own type. That improves readability for me and I am able to use the inner type more easily.

Thinking about that maybe a rule for disallowing non plain unions would be better than a specific array-type based on their content?
For example this would be allowed:

type A = string | string[]
type B = Array<A>
type C = readonly A[]

And this would be disallowed as the unions are not at the top level

type B = Array<string | string[]>
type C = readonly (string | string[])[]

Maybe this could be configurable to allow union of simple types like this: Something<string | boolean> as they are still relatively easy to read.

There is no rule like that currently existing nor an issue suggesting such rule.
For now its just a quick thought that came up, not sure if or how much that improves things. Or maybe I'm overlooking something.

[fregante]

That’s what the array-simple config does exactly: https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/array-type.md

XO’s config already uses array-simple so if it still doesn’t work correctly it should be reported to TS-ESLint. It’s not something XO can fix anyway.