Enhancement: readonly arrays

[laurence-myers]

It would be nice if we could use ReadonlyArray in place of []. Currently, trying to return a ReadonlyArray in a response will fail type checking, because the response requires a mutable array.

e.g.

    ErrorResponse: {
      //errors: components["schemas"]["Error"][]; // old way
      errors: ReadonlyArray<components["schemas"]["Error"]>; // new way
    };

[drwpow]

Interesting! This makes sense to me.

Just for clarification: should all arrays be Readonly in TS generation? My gut instinct would be yes, but I’d like to confirm that’s what you’d think.

[laurence-myers]

Yes, that'd be my preference. 🙂 But it would depend on the codebase, and whether it generally uses immutable data. Some apps might want to add items to an array while building a response, or "pop" items from an input array (e.g. if it's an intermediate proxy), particularly if performance is a concern. Maybe it should be configurable, via CLI option etc.

…

On Thu, 4 Mar. 2021, 2:04 pm Drew Powers, ***@***.***> wrote: Interesting! This makes sense to me. Just for clarification: should *all* arrays be Readonly in TS generation? My gut instinct would be yes, but I’d like to confirm that’s what you’d think. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#501 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABQK4MHG5IQG7DABVFPKVWDTB32EXANCNFSM4YSL4A4Q> .

[drwpow]

That’s a fair point. My initial assumption was to treat it as immutable, but now that you say that, I myself have used this library to generate new structures before sending to an API (e.g. a ReadonlyArray<> would be a pretty bad structure if you were POST-ing something).

I like the idea of a CLI flag that just turns all arrays into ReadonlyArray<>. Looking at the OpenAPI spec, I see readOnly as a schema option, but reading the description of “it MAY be sent as part of a response but SHOULD NOT be sent as part of the request” makes me think that this is something different than your idea. I think your idea is more of a TypeScript concern than a property of your OpenAPI schema, which makes me think a flag may be best.

[dnalborczyk]

I second this. it would be great if we could also make all types immutable, not only arrays.

e.g. graphql-code-generator for typescript has an option to generate immutable types: https://graphql-code-generator.com/docs/plugins/typescript

immutableTypes
type: boolean default: false

Generates immutable types by adding readonly to properties and uses ReadonlyArray

e.g.:

type Foo {
	readonly bar: readonly foobar[]
}