A version of types.maybe which uses undefined instead of null

[pelotom]

In TypeScript especially, undefined is almost always preferable to null as a representation of unset values, so it would be nice if there was a version of types.maybe (types.maybeUndefined?) which used undefined instead of null.

[Bnaya]

you have types.optional, which is i think what you look for

[pelotom]

Yes, you can implement it with optional,

function maybeUndefined<S, T>(type: IType<S, T>): IType<S | undefined, T | undefined> {
  return types.optional(types.union(type, types.undefined), undefined);
}

but it would be cool if it were built in 🙂

[mweststrate]

I think it would be interesting to consider dropping null as default nullable, and use undefined instead. So that for example maybe accepts undefined instead of null, by default etc

[k-g-a]

It seems to me that we could introduce ‘types.nullable’ as direct replacement of current ‘maybe’, and convert ‘maybe’’s default to ‘undefined’, as proposed in previous comment

[mweststrate]

Done! In MST 3 types.maybe will use undefined as default value, and types.maybeNull can be used for the old behavior

[sis-dk]

This doc need an update stating this change?
https://mobx-state-tree.gitbook.io/docs/v/new-docs/types-overview