JSON Schema (lite)

NOT FOR PRODUCTION USE

This is a minimal implementation of JSON Schema 2020-12 with a couple of the more complex features left out. This implementation exists solely to facilitate the qualification task for the JSON Schema GSoC project Better JSON Schema Errors project. Do not use it in production. It will not be maintained or supported.

Qualification Task

There's no better way to get familiar with the JSON Schema output format than to implement it yourself. This implementation currently implements the Flag output format. Your task is to update it to support either the Basic or Detailed output formats. You must include valid, absoluteKeywordLocation, and instanceLocation. Because we aren't implementing the Verbose output format, you don't need to support annotations/annotation. You don't need to support error because we're going to ignore messages from the implementation anyway. keywordLocation is optional because I can't see any reason we'd use it. You must include tests to show that your implementation works including coverage for all implemented keywords.

To submit your qualification task, use npm pack and DM it to me. I will provide one and only one review for each candidate, so make sure you're ready when you submit. You can't fail the qualification task. As long as you submit something, I'll consider your application. However, I will strongly take into consideration the quality of your submission when evaluating applications.

This project uses ESLint. I encourage you to install an ESLint plugin in your editor to get feedback in real time. ESLint is also used for code style checks, but it doesn't check everything, so make an effort to match my code style when making changes.

There are three scripts you should make sure that you are passing before submitting.

• npm test
• npm run lint
• npm run type-check

I strongly encourage you to turn off your AI coding assistants for this exercise. They tend to generate very low quality code. Code that works is just the beginning. It also needs to be maintainable. Sloppy code hides bugs, is hard to maintain, and slows down progress in the long term. This may be throw away code that we're never going to build on later, but remember that part of the goal of this task is to demonstrate your ability to write quality code for a project that will need to evolve and be maintained over the several next years.

About the Implementation

Unsupported features and keywords

• Embedded schemas
• $anchor
• $dynamicRef/$dynamicAnchor
• unevaluatedProperties/unevaluatedItems
• format assertion
• Annotations
• Custom dialect/vocabularies/keywords
• Older dialects
• Retrieving files from the file system or the web

API

• validate(schema: Json, instance: Json) => Output
• registerSchema(schema: Json, uri: string) => void

The Json type represents any JavaScript value that is compatible with JSON.

The Output type represents the Flag output format. It includes the valid property, but no errors.

Example Usage

import { validate } from "../src/index.js";

/**
 * @import { Json } from "./src/jsonast.d.ts"
 */

/** @type Json */
const schema = {
  $ref: "#/$defs/a",
  $defs: {
    a: { type: "number" }
  }
};
const instance = true;
const output = validate(schema, instance);
console.log("valid", output.valid);