Hi,

I stumbled accross your library because we want to properly parse our environment and are already using TypeScritpt. During testing i recognized, that it is currently not possible to set default values for environment variables even if Typebox supports setting of default values.

I stumbled accross this post in the Typebox repo where they implement a proper parsing function. I tested it in my code and it was working as expected. When setting a default value and calling the parse function, the optional properties with a default value are set to their respective default value.

A small example here:

import {Static, TSchema, Type} from '@sinclair/typebox';
import { Value } from '@sinclair/typebox/value';

const Parse = <T extends TSchema>(T: T, value: unknown) => 
  Value.Decode(T,
    Value.Clean(T,
      Value.Default(T,
        Value.Convert(T, value),
      )
    )
  )

const ConfigSchema = Type.Object({
  FOO: Type.Optional(
    Type.String({
      default: 'mydefaultfooval',
    })
  ),
});
type ConfigSchema = Static<typeof Schema>;

env = Parse(ConfigSchema , process.env);

then env would be type of ConfigSchema and the result would be:

{
  FOO: 'mydefaultfooval',
}

Maybe this is something you want to implement?