tag recursion

[sledorze]

I'm currently writing a lib to generate Generators for 'testcheck' (https://github.com/leebyron/testcheck-js) library (btw any constructive criticism on that choice is welcome)

I've covered so far:

interface, string, number, boolean, literal, union, intersection (of recursive unions/intersections of interfaces/partials), array, partial
I can't implement recursion because io-ts currently does not provide a tag on it.
Can it be done?

Thanks!

[gcanti]

I'm currently writing a lib to generate Generators for 'testcheck'

That's a great idea

I can't implement recursion because io-ts currently does not provide a tag on it

What do you need in order to implement recursion?

In the 80 branch you can find a POC (added a RecursiveType type) and you can introspect like this

type ICategory = {
  name: string
  categories: Array<ICategory>
}

const Category = t.recursion('Category', self =>
  t.interface({
    name: t.string,
    categories: t.array(self)
  })
)

console.log(Category._tag) // RecursiveType
console.log(Category.name) // Category
console.log((Category.type as any)._tag) // InterfaceType
const type = Category.type as t.InterfaceType<any>
console.log(type.props.categories.type) // RecursiveType { name: 'Category', ... }

You can try it out with npm i gcanti/io-ts#80

[sledorze]

I've done a quick check (pun intended),
@gcanti that _tag information is all I need, may it be merged?