Creating Upgradable ERC20 token using OpenZeppelin and Buidler plugin

Support Upgrades
7

Hi @Prabhakaran,

I used the steps from OpenZeppelin Upgrades: Step by Step Tutorial for Buidler to setup an environment.

:exclamation: Buidler is now Hardhat. There will be an Upgrades Plugin for Hardhat soon.

I also used Create an ERC20 using buidler, without writing Solidity for interacting.

I created an upgradeable ERC20 token and then interacted with it using the console.

MyToken.sol

(Based on https://github.com/OpenZeppelin/openzeppelin-contracts-ethereum-package/blob/v3.0.0/contracts/presets/ERC20PresetMinterPauser.sol#L35)

// contracts/MyToken.sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;

import "@openzeppelin/contracts-ethereum-package/contracts/Initializable.sol";
import "@openzeppelin/contracts-ethereum-package/contracts/GSN/Context.sol";
import "@openzeppelin/contracts-ethereum-package/contracts/access/AccessControl.sol";
import "@openzeppelin/contracts-ethereum-package/contracts/token/ERC20/ERC20Burnable.sol";
import "@openzeppelin/contracts-ethereum-package/contracts/token/ERC20/ERC20Pausable.sol";

contract MyToken is Initializable, ContextUpgradeSafe, AccessControlUpgradeSafe, ERC20BurnableUpgradeSafe, ERC20PausableUpgradeSafe {
    bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");
    bytes32 public constant PAUSER_ROLE = keccak256("PAUSER_ROLE");

    /**
     * @dev Grants `DEFAULT_ADMIN_ROLE`, `MINTER_ROLE` and `PAUSER_ROLE` to the
     * account that deploys the contract.
     *
     */

    function initialize(string memory name, string memory symbol) public {
        __Context_init_unchained();
        __AccessControl_init_unchained();
        __ERC20_init_unchained(name, symbol);
        __ERC20Burnable_init_unchained();
        __Pausable_init_unchained();
        __ERC20Pausable_init_unchained();

        _setupRole(DEFAULT_ADMIN_ROLE, _msgSender());

        _setupRole(MINTER_ROLE, _msgSender());
        _setupRole(PAUSER_ROLE, _msgSender());
    }

    /**
     * @dev Creates `amount` new tokens for `to`.
     *
     * Requirements:
     *
     * - the caller must have the `MINTER_ROLE`.
     */
    function mint(address to, uint256 amount) public {
        require(hasRole(MINTER_ROLE, _msgSender()), "MyToken: must have minter role to mint");
        _mint(to, amount);
    }

    /**
     * @dev Pauses all token transfers.
     *
     * Requirements:
     *
     * - the caller must have the `PAUSER_ROLE`.
     */
    function pause() public {
        require(hasRole(PAUSER_ROLE, _msgSender()), "MyToken: must have pauser role to pause");
        _pause();
    }

    /**
     * @dev Unpauses all token transfers.
     *
     * Requirements:
     *
     * - the caller must have the `PAUSER_ROLE`.
     */
    function unpause() public {
        require(hasRole(PAUSER_ROLE, _msgSender()), "MyToken: must have pauser role to unpause");
        _unpause();
    }

    function _beforeTokenTransfer(address from, address to, uint256 amount) internal override(ERC20UpgradeSafe, ERC20PausableUpgradeSafe) {
        super._beforeTokenTransfer(from, to, amount);
    }
}

deploy.js

// scripts/deploy.js
const { ethers, upgrades } = require("@nomiclabs/buidler");

async function main() {
  const MyToken = await ethers.getContractFactory("MyToken");
  console.log("Deploying token...");
  const token = await upgrades.deployProxy(MyToken, ["My Token", "TKN"], { unsafeAllowCustomTypes: true  });
  console.log("Token deployed to:", token.address);
}

main();

buidler.config.js

// buidler.config.js
usePlugin('@nomiclabs/buidler-ethers');
usePlugin('@openzeppelin/buidler-upgrades');
 
module.exports = {
    solc: {
        version: '0.6.12',
    },
};

Local network

npx buidler node

Deploy

$ npx buidler run scripts/deploy.js --network localhost
Compiling...

...

Compiled 12 contracts successfully
Deploying token...

Warning: Potentially unsafe deployment of MyToken

    You are using the `unsafeAllowCustomTypes` flag to skip storage checks for structs and enums.
    Make sure you have manually checked the storage layout for incompatibilities.

Token deployed to: 0x0078371BDeDE8aAc7DeBfFf451B74c5EDB385Af7

Interact

$ npx buidler console --network localhost
All contracts have already been compiled, skipping compilation.
> const Token = await ethers.getContractFactory("MyToken")
undefined
> const token = await Token.attach("0x0078371BDeDE8aAc7DeBfFf451B74c5EDB385Af7")
undefined
> await token.name()
'My Token'
> accounts = await ethers.provider.listAccounts()
[ '0xc783df8a850f42e7F7e57013759C285caa701eB6',
  '0xeAD9C93b79Ae7C1591b1FB5323BD777E86e150d4',
...
> await token.mint(accounts[1], "100000000000000000000")
{ hash:
...
> (await token.balanceOf(accounts[1])).toString()
'100000000000000000000'