Noir Codegen for TypeScript

When using TypeScript, it is extra work to interpret Noir program outputs in a type-safe way. Third party libraries may exist for popular Noir programs, but they are either hard to find or unmaintained.

Now you can generate TypeScript bindings for your Noir programs in two steps:

1. Exporting Noir functions using nargo export
2. Using the TypeScript module noir_codegen to generate TypeScript binding

Note: you can only export functions from a Noir library (not binary or contract program types).

Installation

Your TypeScript project

If you don't already have a TypeScript project you can add the module with yarn (or npm), then initialize it:

yarn add typescript -D
npx tsc --init

Add TypeScript module - noir_codegen

The following command will add the module to your project's devDependencies:

yarn add @noir-lang/noir_codegen -D

Nargo library

Make sure you have Nargo, v0.25.0 or greater, installed. If you don't, follow the installation guide.

If you're in a new project, make a circuits folder and create a new Noir library:

mkdir circuits && cd circuits
nargo new --lib myNoirLib

Usage

Export ABI of specified functions

First go to the .nr files in your Noir library, and add the #[export] macro to each function that you want to use in TypeScript.

#[export]
fn your_function(...

From your Noir library (where Nargo.toml is), run the following command:

nargo export

You will now have an export directory with a .json file per exported function.

You can also specify the directory of Noir programs using --program-dir, for example:

nargo export --program-dir=./circuits/myNoirLib

Generate TypeScript bindings from exported functions

To use the noir-codegen package we added to the TypeScript project:

yarn noir-codegen ./export/your_function.json

This creates an exports directory with an index.ts file containing all exported functions.

Note: adding --out-dir allows you to specify an output dir for your TypeScript bindings to go. Eg:

yarn noir-codegen ./export/*.json --out-dir ./path/to/output/dir

Example .nr function to .ts output

Consider a Noir library with this function:

#[export]
fn not_equal(x: Field, y: Field) -> bool {
    x != y
}

After the export and codegen steps, you should have an index.ts like:

export type Field = string;


export const is_equal_circuit: CompiledCircuit = {"abi":{"parameters":[{"name":"x","type":{"kind":"field"},"visibility":"private"},{"name":"y","type":{"kind":"field"},"visibility":"private"}],"param_witnesses":{"x":[{"start":0,"end":1}],"y":[{"start":1,"end":2}]},"return_type":{"abi_type":{"kind":"boolean"},"visibility":"private"},"return_witnesses":[4]},"bytecode":"H4sIAAAAAAAA/7WUMQ7DIAxFQ0Krrr2JjSGYLVcpKrn/CaqqDQN12WK+hPBgmWd/wEyHbF1SS923uhOs3pfoChI+wKXMAXzIKyNj4PB0TFTYc0w5RUjoqeAeEu1wqK0F54RGkWvW44LPzExnlkbMEs4JNZmN8PxS42uHv82T8a3Jeyn2Ks+VLPcO558HmyLMCDOXAXXtpPt4R/Rt9T36ss6dS9HGPx/eG17nGegKBQAA"};

export async function is_equal(x: Field, y: Field, foreignCallHandler?: ForeignCallHandler): Promise<boolean> {
  const program = new Noir(is_equal_circuit);
  const args: InputMap = { x, y };
  const { returnValue } = await program.execute(args, foreignCallHandler);
  return returnValue as boolean;
}

Now the is_equal() function and relevant types are readily available for use in TypeScript.