Unable to JSON serialize type with optional keys

[parkan]

Unable to JSON serialize type with optional keys

[dbartholomae]

Thanks! I've quickly fixed it myself, as the setup with Rush currently is a bit finicky.

[parkan]

Ok, I am not quite able to make the mapped type work here, not really sure how to apply it to the type parameter on JSONObject, what I have so far is

type RequiredKeys<T> = { [k in keyof T]-?: undefined extends T[k] ? never : k }[keyof T];
type PickRequiredKeys<T> = Pick<T, RequiredKeys<T>>

but I'm not sure how to use it in the PromiseHandler signature

EDIT: ok, I am able to get unit tests to pass with

type RequiredKeys<T> = { [k in keyof T]-?: undefined extends T[k] ? never : k }[keyof T];
type PickRequiredKeys<T> = Pick<T, RequiredKeys<T>>

export const jsonSerializer = () => (
  handler: PromiseHandler<APIGatewayEvent, PickRequiredKeys<JSONObject> | undefined>

However, using a mapped type on the type bound in that signature is bending my brain a little bit so I'm not 100% sure it's correct

[parkan]

BTW thanks for being so responsive on these libraries, it seems like you're the only maintainer so I really appreciate it as it as they really fit my usecase and I'm frankly surprised they are not more widely used. This isn't strictly as "bug" as much as a limitation, but there was no better template to use. I'm happy to PR with these changes if they make sense to you, I'm still relatively new to typescript (mostly Scala background for this kind of thing) so I am not entirely sure of myself and appreciate the guidance.

[dbartholomae]

It's released in version 2.1.0
https://www.npmjs.com/package/@lambda-middleware/json-serializer