How to Codegen TypeScript types from TypeBox schemas

[heysokam]

I'm writing a file format similar to the json representation of the glTF spec.

I'm making typebox the one source of truth, so I'm defining the descriptions for the format on the TypeBox schemas description: "Some info here" fields.
That way I can serialize the schemas into sometype.schema.json files and have access to the same doc-comments inside the serialized schema files "compiled" from the typebox the specification.

My goal now is to somehow generate a typescript code file that contains my typebox descriptions preserved as doc-comments.
I'm aware of both type Thing = Static<typeof SomeTypeboxSchema> and typebox-codegen, but I haven't found how to achieve typescript code generation from typebox schemas.

Is there an existing tool to do this type T = ... typescript code generation programmatically?

[potatohoney-p]

For a JSON-compatible file-format schema, you can pass the serialized TypeBox schema to json-schema-to-typescript. Its compile API emits TypeScript source, and description becomes a doc comment. This is different from Static<typeof Schema>, which gives you a type in the current program rather than generating a source file.

For example, save this as generate.mjs:

import { Type } from '@sinclair/typebox'
import { compile } from 'json-schema-to-typescript'
import { writeFile } from 'node:fs/promises'

const Mesh = Type.Object({
  name: Type.String({ description: 'Display name of the mesh.' }),
  vertices: Type.Array(Type.Number(), { description: 'Vertex coordinates.' }),
  visible: Type.Optional(Type.Boolean({ description: 'Whether the mesh is visible.' })),
}, { description: 'A mesh in the file.', additionalProperties: false })

const schema = JSON.parse(JSON.stringify(Mesh))
const source = await compile(schema, 'Mesh', { bannerComment: '' })
await writeFile('mesh.ts', source)

Running node generate.mjs produces:

/**
 * A mesh in the file.
 */
export interface Mesh {
  /**
   * Display name of the mesh.
   */
  name: string;
  /**
   * Vertex coordinates.
   */
  vertices: number[];
  /**
   * Whether the mesh is visible.
   */
  visible?: boolean;
}

If you already have sometype.schema.json, parse that file and pass the parsed schema to compile instead; there is no need to rebuild it with TypeBox. The JSON round-trip above makes the boundary explicit: the generator receives the serialized schema, not TypeBox's symbol metadata.

I checked the exact script with @sinclair/typebox@0.34.41, json-schema-to-typescript@16.0.0, Node 24.22.1 and TypeScript 5.9.3. Seven output assertions checked the four descriptions and the string/array/optional property declarations, and the generated file passed tsc --strict --noEmit --skipLibCheck.

This example covers JSON-compatible schemas, not TypeBox transforms, JavaScript-only types or all recursive/external-reference combinations. The generated declarations also do not replace runtime validation or express every JSON Schema constraint. The generator's README shows the description-to-comment behavior and its programmatic API.

[heysokam]

@potatohoney-p it does not seem to support it? 🤔

(complete schema for reference: https://codeberg.org/heysokam/astTF/src/branch/master/spec)

[potatohoney-p]

I reproduced the screenshot's behavior in the online demo. With your root schema, it tries to fetch https://borischerny.com/id.schema.json and gets HTTP 404. In my reproduction, the right pane still showed the original ExampleSchema after reference resolution failed.

My earlier example was self-contained; I should have included the reference-directory handling needed for your files. Keep the complete spec/ folder locally and use compileFromFile, which resolves the sibling schema files from the input file's directory.

With json-schema-to-typescript@16.0.0 installed, save this as generate.mjs at your repository root and run node generate.mjs:

import { compileFromFile } from 'json-schema-to-typescript';
import { writeFile } from 'node:fs/promises';

const source = await compileFromFile('spec/astTF.schema.json', {
  bannerComment: '',
});
await writeFile('asttf-types.ts', source);

I tested that exact script against the complete JSON schema set from your linked repository at commit e33078a52f6766d39be25bf377470479c028161e, using Node 24.22.1. It generates the AST types, and the result passes TypeScript 5.9.3 with --strict --exactOptionalPropertyTypes --noEmit --skipLibCheck. The root description and the metadata, root, and data descriptions are present. If you keep using compile(parsedSchema, ...), pass cwd as the directory containing those schema files instead.

There is a documentation caveat: some $ref property descriptions become comments on the emitted referenced declarations, and a description beside $ref can replace the referenced schema's own description. I confirmed that with your metadata reference. So this fixes generation for your files, but it does not guarantee a one-to-one preservation of every comment's location or wording.

[heysokam]

Thank you for spending your tokens on my repo, I guess?
I really don't know how to respond to this. If I wanted an agent interaction I would have prompted one myself 🤷

[heysokam]

Reason for closing: AI bot necrobump.
I'd rather solve it myself if 1year later, after I already forgot this post even existed, all the response I get is some chatbot automation.
I have no patience for this.