xERC20 is a standard for bridged tokens. A common interface to be used across different implementations of bridges to keep liquidity concentrated and improve user experience on-chain.

XERC20: A standard for bridges to manage the same liquidity when bridging. It allows its owner to approve bridges and add limits to them for minting and burning the XERC20 token. The XERC20 standard is compatible with two different types of bridge behaviours, bridges calling mint/burn from the user (or other function names through adapters) and bridges that transfer from the user to the bridge contract. On the latter, XERC20 tokens that are received by the bridge get burned and when a bridge transfers tokens out, they get minted again.

XERC20Lockbox: The lockbox works as a wrapper of an ERC20. It mints XERC20 tokens at a 1:1 ratio when receiving ERC20 tokens and it unlocks the ERC20 the other way around. The lockbox can be deployed on any chain that has a canonical token representation, chains that do not currently have a canonical representation can avoid deploying a Lockbox and use the XERC20 as the default implementation for the chain.

XERC20Factory: The factory is used as a helper to deploy an xToken. It allows the owner to deploy the XERC20 and the Lockbox in one transaction while keeping the same token address on every chain used.

^{*The adapter included is an example into how it would work. Any bridge can build their own.}

1. Install Foundry by following the instructions from their repository.
2. Copy the .env.example file to .env and fill in the variables
3. Install the dependencies by running : yarn install && forge install

The default way to build the code is suboptimal but fast, you can run it via:

yarn build

In order to build a more optimized code (via IR), run:

yarn build:optimized

Unit tests should be isolated from any externalities, while E2E usually run in a fork of the blockchain. In this boilerplate you will find example of both.

In order to run both unit and E2E tests, run:

yarn test

In order to just run unit tests, run:

yarn test:unit

In order to run unit tests and run way more fuzzing than usual (5x), run:

yarn test:unit:deep

In order to just run e2e tests, run:

yarn test:e2e

In order to check your current code coverage, run:

yarn coverage

⚠ WARNING: Forge coverage is having some issues...
As stated in this github issue, checking the code coverage with Forge when using abstract contract is not currently working.

Configure the .env variables.

ℹ️ Notice: _Please ensure that all private keys (PKs) are prefixed with 0x before using or submitting them. This prefix is necessary for proper formatting and compatibility.*

Example:
- Correct: `0x123abc...`
- Incorrect: `123abc...`

You will need to set your custom name and symbol for your XERC20 to be deployed, no need to add an 'x' infront of it, the contract will do that for you. For more details check the section below.

This guide provides a detailed, step-by-step process to deploy an xERC20 token using this repository. We will first demonstrate how to deploy the xERC20 token alone, and then we’ll cover the scenario in which you want to deploy both the xERC20 token and the lockbox.

Locate and open the MultichainCreateXERC20.sol file, which should be situated within the solidity/scripts directory.

Decide on which blockchains you want to deploy your token. For this example, we will choose Ethereum mainnet, Polygon, and Gnosis. Add the required chains to the chains array in the MultichainCreateXERC20.sol file like so:

string[] public chains = ['MAINNET_RPC', 'POLYGON_RPC', 'GNOSIS_RPC'];

Ensure that you have the corresponding RPC URLs added in your .env file to support these networks. Refer to this section for more information on setting up your environment variables.

Update the token name and symbol in your smart contract. For this guide, we are setting the name of the token to "Setup Token" and the symbol to "SToken". Make the changes on lines 31 and 32 in your smart contract code.

ℹ️ Important Note: An address cannot deploy a token with the same name and symbol more than once on any given chain. Ensure that you have not previously deployed a token with the same name or symbol using your address.

string memory name = 'Setup Token';
string memory symbol = 'SToken';

Save your changes to proceed.

Ensure that everything in your smart contract is set up correctly and free of errors by compiling it with the following command:

yarn build

You should see a confirmation in your terminal, similar to the screenshot below:

Before proceeding with the actual deployment of your token, it is crucial to perform a dry-run. This helps in verifying the deployment process and estimating the gas costs on all the selected chains. Run the following command to initiate a dry-run:

yarn run script:DeployXERC20

You will receive the xERC20 token address, transaction details, and gas estimates as shown in the screenshots below:

You are now at the final step of the deployment process. With all the previous steps successfully completed, you are ready to deploy your xERC20 token to the selected blockchain networks. Run the following command to initiate the deployment:

yarn run script:DeployXERC20:broadcast

Congratulations! You have successfully deployed your xERC20 token. 🚀

Integrating xERC20 with a Lockbox requires a few additional steps, yet the process remains straightforward. Prior to embarking on this journey, ensure that you have completed steps 1-3 from the previous section, focusing on code modifications.

Assuming you have navigated through the initial steps successfully, let’s dive into the integration of xERC20 with Lockbox:

Identify the blockchain networks where your token is already deployed and cannot be converted to xERC20. On these specific networks, a Lockbox will be required to facilitate interactions.

Next, in the same MultichainCreateXERC20.sol file, specify the canonical token addresses for the chains requiring a Lockbox. Here’s how to do it:

ℹ️ Important Note: Ensure alignment between the address or canonical token and the chains array. For chains not requiring a Lockbox, you can either leave the address field blank or use the ZERO address.

// Example:

// Chains for xERC20 deployment
string[] public chains = ['MAINNET_RPC', 'POLYGON_RPC', 'GNOSIS_RPC'];

// Canonical token addresses for Lockbox
// (assuming MAINNET requires a Lockbox, others do not)
address[] public erc20 = [
    address(0x123...abc), // Canonical token on MAINNET
    address(0),           // No Lockbox for POLYGON
    address(0)            // No Lockbox for GNOSIS
];

// Alternatively, focusing solely on MAINNET:
address[] public erc20 = [
    address(0x123...abc) // Canonical token on MAINNET
];

With everything now configured, proceed by following the steps outlined in the “Deploying xERC20 Without the Lockbox” section. This includes building and deploying your contracts, ensuring a seamless integration of xERC20 and Lockbox.

Before deploying your xERC20 token along with the Lockbox, it’s essential to conduct a dry-run. This ensures everything is set up correctly and provides you with gas estimates for all selected chains, as well as the addresses for your xERC20 token and the Lockbox.

Run the following command to start the dry-run:

yarn run script:DeployXERC20

Upon completion, you will receive output detailing the xERC20 token address, the Lockbox address, transaction details, and gas estimates. Below is an example of what your terminal might display:

Here you can see lockbox addresses 🚀.

Now broadcast it and you are good to go.

The deployments are stored in ./broadcast

See the Foundry Book for available options.