Validation Combinators (using `Decoder`)

[anthonyjoeseph]

🚀 Feature request

yup, joi, zod, superstruct, ajv, and validate.js all have a big library of combinators for the sake of validation

io-ts is a 'runtime type system' This PR is meant to expand it into a 'runtime validation' system

Using 'decoders' b/c they compose

Current Behavior

Validation combinators must be implemented manually

Desired Behavior

An extensive, verbose & granular library of common validators

Suggested Solution

By type:

• Array

  • length
  • minLength
  • elem
  • isUniq
  • intersects

• boolean

  • fromString
  • fromNumber

• date

  • UnknownDate
  • fromISOString
  • fromISOStringCoerce
  • fromNumber
  • fromUnixTime

• Either

  • either

• Error (Decoder errors)

  • recoverWith
  • replace

• Eq

  • is
  • oneOf
  • keyMatches

• json

  • fromString

• NewType

  • fromCarrierOf

• NonEmptyArray

  • UnknownNonEmptyArray
  • fromArray

• number

  • truncate
  • precision
  • maxPrecision
  • port
  • floor
  • round
  • abs
  • negate
  • positive
  • negative
  • parseInt

• Option

  • option

• Ord

  • lt
  • gt
  • leq
  • geq
  • between

• Set

  • UnknownSet
  • fromArray

• string

  • length
  • minLength
  • truncate
  • nonEmptyString
  • alphanumerical
  • base64
  • creditCard
  • dataUri
  • domainName
  • email
  • hex
  • hostname
  • ip
  • isoDate
  • isoDuration
  • normalize
  • regex
  • token
  • uri
  • uuid

partial implementation (playground)

The decoders & combinators are split into four categories:

• Refine - these decoders will only narrow the type
• Parse - these decoders will change the type arbitrarily
• Build - these combinators will build decoders from other decoders
• Util - simple refinements & endomorphisms used to create decoders

Hopefully, enough implementation is specified to understand the intent

If I made a PR of this or some subset of it, would you consider it?

Who does this impact? Who is this for?

Users looking for a runtime validation library

Describe alternatives you've considered

A fork of this library, or maybe new one entirely? io-ts-validations? io-ts-decoders?

Maybe the decoders that are simply 'maps', with no chance of failure (e.g. string.truncate) could purely live in Util, since they're trivial to implement as Decoders?

Additional context

closes https://github.com/gcanti/io-ts-types/issues/151 closes https://github.com/gcanti/io-ts-types/issues/59

Your environment

Software	Version(s)
fp-ts	2.11.8
io-ts	2.2+
io-ts-types	N / A
TypeScript	3.5.0+