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Introduction to Hardhat
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apothem
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hardhat
What Hardhat is, what it is used for, and how to use it for development on the XDC Network.

Hardhat

🧭 Table of contents

📰 Overview

hardhat

Hardhat is a development environment to compile, deploy, test, and debug your Ethereum software. Get Solidity stack traces & console.log.

What you will learn

This article will teach you what Hardhat is, what Hardhat is used for, and how to use the features of Hardhat for development on the XDC Network.

What you will do

  • What Hardhat is
  • How to create and configure Hardhat project
  • Overview of Hardhat tasks
  • Hardhat plugins

📰 About Hardhat

Hardhat is development which lets you compile and deploy smart contracts on Eethereum-like networks. Hardhat has extensible tooling platform, solidity debugger, plugin ecosystem, Typescript support and more. It is one of the most popular development environments along with Remix and Truffle.

Why do you need development environment

Deploying smart contracts is a very complex task and can cost you a lot of money if you do it wrong, that's why you need to use development environment like Hardhat.

Hardhat comes with lots of tools out of the box which make you life easier and increase your productivity as dApp developer. Hardhat debugging and testing tools allow you to weed out bugs and vulnerabilities in your smart contract before deploying it to live network.

⚒ Create Hardhat Project

To create new Hardhat run this command:

npx hardhat

Hardhat gives your three options how to initialize your project:

 What do you want to do? … 
▸ Create a JavaScript project
  Create a TypeScript project
  Create an empty hardhat.config.js

You can choose to create Javascript or Typescript project, which will create hardhat.config.js and contracts, scripts, test with some example files. Or you can just create empty hardhat.config.js file and do everything by yourself.

⚒ Hardhat folder structure

Hardhat has the following folders:

  • artifacts: place where smart contract compilation artifacts are stored
  • cache: folder used for caching internal data
  • contracts: folder for smart contract source code
  • scripts: folder where scripts which interact with Hardhat Runtime Environment are stored including script for deploying your smart contracts
  • test: place to store tests

⚒ Hardhat Config

Hardhat config is stored in hardhat.config.js. Config defines which network and accounts hardhat will use, which version of compiler it will run, can be used to configure custom folder structure or configure tests.

Here is an example of hardhat config:

module.exports = {
  defaultNetwork: "rinkeby",
  networks: {
    hardhat: {
    },
    rinkeby: {
      url: "https://eth-rinkeby.alchemyapi.io/v2/123abc123abc123abc123abc123abcde",
      accounts: [privateKey1, privateKey2, ...]
    }
  },
  solidity: {
    version: "0.5.15",
    settings: {
      optimizer: {
        enabled: true,
        runs: 200
      }
    }
  }
}
  • defaultNetwork: network which is used by default when you run hardhat
  • networks: list of blockchain networks you will use
    • url: JSON-RPC url of network
    • accounts: list of accounts you will use to interact with network
  • solidity: solidity compiler configuration

You can read more about Hardhat configuration here: Hardhat Configuration.

⚒ Hardhat Tasks

Hardhat task is a command that automates things like deploying, compiling, testing and more. Hardhat comes with some tasks out of box, but you can always define your own tasks using the same Hardhat API.

Open hardhat console:

npx hardhat console

Welcome to Node.js v16.11.1.
Type ".help" for more information.
>

Compile contracts:

npx hardhat compile

Compiled 1 Solidity file successfully

Running tests:

npx hardhat test

  Lock
    Deployment
      ✔ Should set the right unlockTime (730ms)
      ✔ Should set the right owner
      ✔ Should receive and store the funds to lock
      ✔ Should fail if the unlockTime is not in the future
    Withdrawals
      Validations
        ✔ Should revert with the right error if called too soon
        ✔ Should revert with the right error if called from another account
        ✔ Shouldn't fail if the unlockTime has arrived and the owner calls it
      Events
        ✔ Should emit an event on withdrawals
      Transfers
        ✔ Should transfer the funds to the owner


  9 passing (927ms)

Running scripts (for example deploying):

npx hardhat run scripts/scriptName.js --network yourNetwork

Clears cache and deletes all articats:

npx hardhat clean

To flatten your smart contract in case it uses imports:

npx hardhat flatten > Contract_flat.sol

You can explore more built-in tasks by running:

npx hardhat help

Or get full information on a specific task by running

npx hardhat help taskName

⚒ Hardhat Debugger

You can print messages when testing you smart contract by using console.log().

To do this, import hardhat/console.sol in your project:

pragma solidity ^0.8.9;

import "hardhat/console.sol";

contract Token {
  //...
}

And then add console.log anywhere in your code:

    ...
    function hello() public {
        console.log('hello');
    }
    ...

Now you can add:

await myContract.hello();

somewhere in your tests code and once it reaches this line of code in smart contract it will print hello in the console!

⚒ Hardhat Plugins

Hardhat plugins are extensions that add new functionality to Hardhat.

Some of popular Hardhat plugins are:

  • @nomiclabs/hardhat-ethers: injects ethers.js into Hardhat Runtime Environment
  • @nomiclabs/hardhat-web3: injects Web3 into Hardhat Runtime Environment
  • @typechain/hardhat: typechain support for hardhat

You can explore hardhat plugins on Hardhat Plugins homepage.

To add new plugin simply run:

npm install @nomiclabs/hardhat-ethers

And then add it to Hardhat by putting require in hardhat.config.js:

require("@nomiclabs/hardhat-ethers");

⚒ Using Hardhat to develop on XDC

Hardhat development experience on XDC is mostly indistinguishable from any other Ethereum-like network, but there are still some things you need to learn before starting developing on XDC.

⚒ Configuring XDC Mainnet and Apothem Testnet on Hardhat

In order to get started deploying new contracts on XDC Mainnet and/or Apothem, we need to install a new dependency called dotenv that will be used in the hardhat.config.js file:

npm install dotenv

We will need to configure a .env file with XDC Mainnet and Apothem Testnet RPC endpoints, plus the Private Key of the wallet we are using for deployment. Lets start by running:

touch .env

And writting the following info in our .env file:

XINFIN_NETWORK_URL=https://erpc.xinfin.network
APOTHEM_NETWORK_URL=https://erpc.apothem.network
PRIVATE_KEY=202e3c9d30bbeca38d6578659919d4c3dc989ae18c16756690877fdc4dfa607f

🚨 Do not use the Private Key in the example above in production or you can risk losing your assets! 🚨

And finally, we can configure the hardhat.config.js file for both Apothem and XinFin Networks by writting:

require("@nomicfoundation/hardhat-toolbox");
require('dotenv').config();

module.exports = {
  solidity: "0.8.16",
  networks: {
    xinfin: {
      url: process.env.XINFIN_NETWORK_URL,
      accounts: [process.env.PRIVATE_KEY],
    },
     apothem: {
      url: process.env.APOTHEM_NETWORK_URL,
      accounts: [process.env.PRIVATE_KEY]
    }
  },
};

And now you can deploy and interact with your contracts on XDC mainnet by running:

npx hardhat run scripts/myScript.js --network xinfin

or on testnet:

npx hardhat run scripts/myScript.js --network apothem

For more information about Hardhat, Please Visit Hardhat Documentation.
For more information about XinFin Network, Please Visit XDC Network Documentation on GitBook.\