arktype

toJsonSchema config

Some ArkType features don't have JSON Schema equivalents. By default, toJsonSchema() will throw in these cases.

This behavior can be configured granularly to match your needs.

const T = type({
	"[symbol]": "string",
	birthday: "Date"
})

const schema = T.toJsonSchema({
	fallback: {
		// ✅ the "default" key is a fallback for any non-explicitly handled code
		// ✅ ctx includes "base" (represents the schema being generated) and other code-specific props
		// ✅ returning `ctx.base` will effectively ignore the incompatible constraint
		default: ctx => ctx.base,
		// handle specific incompatibilities granularly
		date: ctx => ({
			...ctx.base,
			type: "string",
			format: "date-time",
			description: ctx.after ? `after ${ctx.after}` : "anytime"
		})
	}
})

const result = {
	$schema: "https://json-schema.org/draft/2020-12/schema",
	type: "object",
	properties: {
		// Date instance is now a date-time string as specified by the `date` handler
		birthday: { type: "string", format: "date-time", description: "anytime" }
	},
	required: ["birthday"]
	// symbolic index signature ignored as specified by the `default` handler
}

a default handler can also be specified at the root of a fallback config:

const T = type({
	"[symbol]": "string",
	birthday: "Date"
})

//--- cut ---

const schema = T.toJsonSchema({
	// "just make it work"
	fallback: ctx => ctx.base
})

These options can also be set at a global or scope-level.

Fallback Codes

This is the full list of configurable reasons toJsonSchema() can fail.

cyclic types can now be converted to JSON Schema

// previously this threw
const schema = type("object.json").toJsonSchema()

// now generates the following schema
const result = {
	$ref: "#/$defs/intersection11",
	$defs: {
		intersection11: {
			type: "object",
			additionalProperties: { $ref: "#/$defs/jsonData1" }
		},
		jsonData1: {
			anyOf: [
				{ $ref: "#/$defs/intersection11" },
				{ type: "number" },
				{ type: "string" },
				{ type: "boolean" },
				{ type: "null" }
			]
		}
	}
}

temporarily disable discrimination for cyclic unions

This addresses multiple issues while we work on a permanent solution for accurately discriminating cyclic unions, tracked here.