annotations reset optional schema types to regular schemas

[Datner]

🐛 Bug report

Current Behavior

const foo = pipe(S.string, S.optional) // S.OptionalSchema<string, true>
const bar = pipe(S.string, S.optional, S.description('...')) // S.Schema<string>

Expected behavior

const foo = pipe(S.string, S.optional) // S.OptionalSchema<string, true>
const bar = pipe(S.string, S.optional, S.description('...')) // S.OptionalSchema<string, true>

Reproducible example

const foo = pipe(S.string, S.optional) // S.OptionalSchema<string, true>
const bar = pipe(S.string, S.optional, S.description('...')) // S.Schema<string>

Suggested solution(s)

add an overload for optional schema

Additional context

// this works, but yeah
const id = pipe(S.string, S.description('...'), S.optional)

Your environment

My personal computer ❤️
Which versions of @fp-ts/schema are affected by this issue? Did this work in previous versions of @fp-ts/schema?
I didn't do regression checks, no idea

Software	Version(s)
@fp-ts/schema	0.1.2
TypeScript	4.9.4

[Giulio Canti]

add an overload for optional schema

This would be rather inconvenient, every schema combinator should take it into account.

That a field is optional is a volatile and local information that serves only to struct for how its API is made, and optional makes sense only used inside struct, it does not have a broader meaning.

So I would try to do the opposite, that is, I would try to make the use of optional even more local and restrictive by preventing an operation like this:

// this should raise a compiler error
pipe(S.string, S.optional, S.description('...'))

and forcing optional to be used as a final wrapper of a Schema

pipe(S.string, S.description('...'), S.optional)