Question: how to implement a basic object schema?

[jsumners]

Basically, I want to implement this test with fluent-schema -- https://github.com/fastify/fast-json-stringify/blob/06acd3bf09a6c0136eb442d0d95e2a5b1fd85cf2/test/additionalProperties.test.js#L68-L79

My attempt keeps resulting in various errors -- https://runkit.com/embed/ep1pfme4238t

var fastJson = require('fast-json-stringify')
var fluent = require("fluent-schema")
var schema = fluent.object().prop(
    'error',
    fluent.object().additionalProperties(true).prop('message')
)
console.log(schema.valueOf())
var stringify = fastJson(schema.valueOf())
stringify({ error: { message: 'foo', code: 'internal_server_error' } })

[aboutlo]

I don't know how it works fastJson in details but I have the feeling the issue could be there

to me

{
    title: 'check string coerce',
    type: 'object',
    properties: {},
    additionalProperties: true
  }

become

const schema = S.object().additionalProperties(true).title('title string coerce')
console.log(JSON.stringify(schema.valueOf(),undefined,2))

which will generate

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "additionalProperties": {},
  "title": "title string coerce"
}

I wonder about additionalProperties: true it isn't required to be set as true because by default a schema accepts an object with extra props. additionalProperties: true will be translated as additionalProperties: {}

So either you set to false or you pass a schema to specify which kind of extra props you want.

[jsumners]

Without additionalProperties:true fast-json-stringify will strip properties that are not explicitly stated in the schema.

[aboutlo]

So looking to the reference:
https://json-schema.org/latest/json-schema-validation.html#rfc.section.6.5.6

The value of "additionalProperties" MUST be a valid JSON Schema.

So the bug is here: https://github.com/fastify/fluent-schema/blob/73adbf43075104d5ac05a874313fd7dbbda72474/src/ObjectSchema.js#L52-L52

we should need something like this:

additionalProperties: value => {
      if (typeof value !== 'boolean' && !isFluentSchema(value))
        throw new Error("'additionalProperties' must be a boolean or a FluentSchema object")
      const attribute =
        typeof value === 'boolean'
          ? value.valueOf()
          : omit(value.valueOf(), ['$schema'])
      return setAttribute({ schema, ...options }, [
        'additionalProperties',
        attribute,
        'array',
      ])
    }

[jsumners]

FYI: re-reading this issue this morning I noticed that I left out a "not" in my last reply. Please re-read it to make sure it still makes sense.

[aboutlo]

Still, a bug in fluent because of the spec

given

const schema = S.object().additionalProperties(true).title('title string coerce')

expect:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "additionalProperties": true,
  "title": "title string coerce"
}

rather than:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "additionalProperties": {},
  "title": "title string coerce"
}

However, additionalProperties: {} is valid it means don't strip
I found somewhere else where they are discussing the same topic: OAI/OpenAPI-Specification#668 (comment)

[aboutlo]

PR merged

[jsumners]

Thank you.