For the last few months, I have had to pause the development of rescript-rest because an important feature was missing in my other library, rescript-schema. I finally managed to implement it, and I am happy to announce the release of ReScript Schema V7 as well as the continuation of rescript-rest development.

ReScript Schema V7

S.object superpowers

I needed this for rescript-rest, and I hope it will be useful for many other rescript-schema users.

s.flatten

Now, it’s possible to spread/flatten an object schema in another object schema, allowing you to reuse schemas in a more powerful way.

type entityData = {
  name: string,
  age: int,
}
type entity = {
  id: string,
  ...entityData,
}

let entityDataSchema = S.object(s => {
  name: s.field("name", S.string),
  age: s.field("age", S.int),
})
let entitySchema = S.object(s => {
  let {name, age} = s.flatten(entityDataSchema)
  {
    id: s.field("id", S.string),
    name,
    age,
  }
})

s.nestedField

A new nice way to parse nested fields:

let schema = S.object(s => {
  {
    id: s.field("id", S.string),
    name: s.nestedField("data", "name", S.string)
    age: s.nestedField("data", "name", S.int),
  }
})

Object destructuring

Also, it’s possible to destructure object field schemas inside of the definition. You could also notice it in the s.flatten example

let entitySchema = S.object(s => {
  let {name, age} = s.field("data", entityDataSchema)
  {
    id: s.field("id", S.string),
    name,
    age,
  }
})

While the example with s.flatten expect an object with the type {id: string, name: string, age: int}, the example above and with s.nestedField will expect an object with the type {id: string, data: {name: string, age: int}}.

Extend field with another object schema

You can define object field multiple times to extend it with more fields:

let entitySchema = S.object(s => {
  let {name, age} = s.field("data", entityDataSchema)
  let additionalData = s.field("data", s => {
    "friends": s.field("friends", S.array(S.string))
  })
  {
    id: s.field("id", S.string),
    name,
    age,
    friends: additionalData["friends"],
  }
})

Destructuring works only with not-transformed object schemas. Be careful since it’s not protected by type system.

Autocomplete improvements

Updated context type names to s for better auto-complete in your IDE.

• effectCtx → s
• Object.ctx → Object.s
• Tuple.ctx → Tuple.s
• schemaCtx → Schema.s
• catchCtx → Catch.s

S.json redesign

Added unsafe mode for S.json:

• S.json → S.json(~validate: bool)
• More flexible
• Improved tree-shaking
• Tools using rescript-schema can get the info from the tagged type: JSON → JSON({validated: bool})

Other cool changes and sometimes breaking

• Added serializeToJsonStringOrRaiseWith

• Allow to create S.union with a single item

• Removed s.failWithError. Use S.Error.raise instead

• PPX: Removed @schema for type expressions. Use @s.matches instead.

• Removed async support for S.union. Please create an issue if you used the feature

• Improved parsing performance of S.array and S.dict ~3 times

• Automatic serializing stopped working for tuples/objects/unions of literals. Use S.literal instead

• Removed InvalidTupleSize error code in favor of InvalidType

• Changed payload of Object and Tuple variants in the tagged type

• Redesigned Literal module to make it more efficient

  • The S.Literal.t type was renamed to S.literal, became private and changed structure. Use S.Literal.parse to create instances of the type
  • S.Literal.classify → S.Literal.parse
  • S.Literal.toText → S.Literal.toString. Also, started using .toString for Function literals and removed spaces for Dict and Array literals to make them look the same as the JSON.stringify output

• Moved built-in refinements from nested modules to improve tree-shaking:

  • S.Int.min → S.intMin

  • S.Int.max → S.intMax

  • S.Int.port → S.port

  • S.Float.min → S.floatMin

  • S.Float.max → S.floatMax

  • S.Array.min → S.arrayMinLength

  • S.Array.max → S.arrayMaxLength

  • S.Array.length → S.arrayLength

  • S.String.min → S.stringMinLength

  • S.String.max → S.stringMaxLength

  • S.String.length → S.stringLength

  • S.String.email → S.email

  • S.String.uuid → S.uuid

  • S.String.cuid → S.cuid

  • S.String.url → S.url

  • S.String.pattern → S.pattern

  • S.String.datetime → S.datetime

  • S.String.trim → S.trim

  • S.Int.min → S.intMin

  • S.Int.max → S.intMax

  • S.Number.max → S.numberMax/S.integerMax

  • S.Number.min → S.numberMin/S.integerMin