JSONSchema not working as expected with `S.optional` about effect HOT 4 CLOSED

Ah, I see - thanks again!

For our use case, we're almost always using @effect/schema to validate user-supplied data.

I'll look into how we can do that programatically, as we have a large number of schemas that I'd like to create JSON schemas for.

from effect.

JSONSchema.make(schema) returns a json schema for the To type of the provided schema, so in this case:

{
    readonly name: string;
    readonly age: number;
    readonly country?: string;
}

in the type above both name and age are required so you get required: [ 'name', 'age' ] which is correct

from effect.

Hi @gcanti, thanks for the prompt reply.

In our case we need a schema for from - as it's a schema for user-supplied data. Perhaps JSONSchema.make() could have an option for making the JSON schema using from or to?

We can make this work by using S.from(Person), however we then lose all annotations from the resulting schema. Do you have any suggestions to get this to work with annotations?

from effect.

Note that annotations are always added to the To side as well, so adding the annotation S.description('An optional age.') to the required field age is not appropriate.

What you want to do is add an annotation to a schema for user-supplied data (where the age field is optional) and then define a transformation that applies a default to the optional field to obtain a required field.

import * as S from "@effect/schema/Schema"
import * as JSONSchema from "@effect/schema/JSONSchema"

const PersonFrom = S.struct({
  name: S.string,
  age: S.optional(S.number, { exact: true }).pipe(S.propertySignatureAnnotations({ description: "An optional age." })),
  country: S.optional(S.string, { exact: true }).pipe(
    S.propertySignatureAnnotations({ description: "An optional country." })
  )
})

const PersonTo = S.struct({
  name: S.string,
  age: S.number,
  country: S.optional(S.string, { exact: true })
})

const Person = S.transform(
  PersonFrom,
  PersonTo,
  (pf) => ({ ...pf, age: pf.age ?? 0 }),
  (pt) => pt
)

console.log(JSONSchema.make(PersonFrom))
/*
{
  '$schema': 'http://json-schema.org/draft-07/schema#',
  type: 'object',
  required: [ 'name' ],
  properties: {
    name: { type: 'string', description: 'a string', title: 'string' },
    age: {
      type: 'number',
      description: 'An optional age.',
      title: 'number'
    },
    country: {
      type: 'string',
      description: 'An optional country.',
      title: 'string'
    }
  },
  additionalProperties: false
}
*/

from effect.