JSON Schema → Luau Type Converter (Rust)

[amirfarzamnia]

JSON Schema → Luau Type Converter (Rust)

I built a Rust-based converter that takes a JSON Schema file and produces Luau type definitions. It’s intended for standard Luau, not just Roblox, and avoids assuming any engine-specific environment. If you’re using Luau in tooling, CLIs, game engines, or embedded environments, this should work out of the box.

The goal was simple: preserve as much of JSON Schema as Luau’s type system can reasonably represent, while keeping the output clean and predictable.

What it supports

• Full JSON Schema primitives (string, number, integer, boolean, null)

• Objects, arrays, enums, const

• $ref, definitions, $defs (always exported, never inlined)

• allOf, anyOf, oneOf

• Required vs. optional semantics

• Constraints preserved as Luau comments:

  • @minimum, @maximum, @pattern, @minItems, etc.

• CLI + library API

• Clear, type-safe error reporting

Example

Input Schema:

{
  "type": "object",
  "properties": {
    "name": { "type": "string" },
    "age": { "type": "number", "minimum": 0, "maximum": 120 }
  },
  "required": ["name"]
}

Generated Luau:

export type Root = {
    --- @minimum 0
    --- @maximum 120
    age: number?,
    name: string,
}

CLI usage

json-schema-to-luau schema.json -o types.luau
cat schema.json | json-schema-to-luau -
json-schema-to-luau schema.json --type-name MyType

Library usage

use json_schema_to_luau::convert_schema;

let output = convert_schema(json_schema_text)?;

Design notes

• Luau isn’t TypeScript, so certain JSON Schema features can’t be expressed directly.
• Numeric literal enums collapse to number.
• Tuple schemas, conditional schemas, and remote $refs are intentionally unsupported.
• allOf merges object properties if present; otherwise becomes an intersection.

These behaviors are documented in the README.

Installation

Crate:

cargo add json-schema-to-luau

CLI:

cargo install json-schema-to-luau

Repo

https://github.com/amirfarzamnia/json-schema-to-luau