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Hardhat

Hardhat is a development environment for smart-contracts that aids editing, compiling, debugging and deploying smart contracts and dApps.

In practice it's a local development enviroment for solidity that spins up the ethereum network for development and gives you fake ETH, and fake test accounts to work with the smart contract being developed. Also, it handles the owner address for you as well.

hre ​

HRE (the Hardhat Runtime Environment) is an object containing all the functionality Hardhat exposes when running a task, test or script.

Every time you run a hardhat command the hre object is built on the fly using the hardhat.config.js.

hardhat.config.js ​

ts
import { HardhatUserConfig } from "hardhat/config";
import "@nomicfoundation/hardhat-toolbox";
require("dotenv").config();

const config: HardhatUserConfig = {
  solidity: "0.8.17",
  networks: {
    goerli: {
      url: process.env.STAGING_QUICKNODE_KEY,
      accounts: [process.env.PRIVATE_KEY!],
    },
  },
};

export default config;

Defines the solidity version to be used and blockchains to target.

[!danger] Mind the compiler version

The compiler version set by pragmas in *.sol files has to be the same as in hardhat.config.js.

In this case the Goerli network is defined through QuickNode:

run.ts and deploy.ts ​

Hardhat can be used to locally run the smart contract and to deploy it to an Ethereum network.

Typically it's good to create 2 files in /scripts/:

  • run.ts
  • deploy.ts

[!danger] Hardhat is very strict about project tree

sh
npx hardhat run scripts/run.ts
npx hardhat run scripts/deploy.ts --network goerli

run.ts ​

sh
npx hardhat run scripts/run.ts

Used for compiling the smart contract, running it, testing and debugging locally.

Hardhat will create a local Ethereum network, just for this contract. After the script completes it'll destroy that local network. Every time you run the contract, it'll be a fresh blockchain.

ts
// WavePortal is the contract name

const main = async () => {
  // get an owner and the non-owner addresses for testing
  const [owner, randomPerson] = await hre.ethers.getSigners();

  // compile the contract and generate necessary files under `/artifacts` dir
  const waveContractFactory = await hre.ethers.getContractFactory("WavePortal");

  // deploy the smart contract to a local network and wait for the deployment to finish
  const waveContract = await waveContractFactory.deploy();
  await waveContract.deployed();

  console.log("Contract deployed to:", waveContract.address);
  console.log("Contract deployed by:", owner.address);

  // get waves from `view` function
  await waveContract.getTotalWaves();

  // make wave transactino
  const waveTxn = await waveContract.wave();

  // wait for the transaction to be mined
  await waveTxn.wait();
  await waveContract.getTotalWaves();
};

const runMain = async () => {
  try {
    await main();
    process.exit(0);
  } catch (error) {
    console.log(error);
    process.exit(1);
  }
};

runMain();

deploy.ts ​

sh
npx hardhat run scripts/deploy.ts --network goerli

Used to deploy to a real blockchain (in this case to Goerli Testnet).

ts
const main = async () => {
  // get an owner address for deployment (the person who deploys)
  const [deployer] = await hre.ethers.getSigners();

  // get the owners balance
  const accountBalance = await deployer.getBalance();

  console.log("Deploying contracts with account: ", deployer.address);
  console.log("Account balance: ", accountBalance.toString());

  const waveContractFactory = await hre.ethers.getContractFactory("WavePortal");
  const waveContract = await waveContractFactory.deploy({
    // funding the contract
    value: hre.ethers.utils.parseEther("0.001"),
  });
  await waveContract.deployed();

  console.log("WavePortal address: ", waveContract.address);
};

const runMain = async () => {
  try {
    await main();
    process.exit(0);
  } catch (error) {
    console.log(error);
    process.exit(1);
  }
};

runMain();

Funding the contract ​

During the deployment it's possible to fund the contract so it can send money to the users who interact with it (e.g. for prizes).

hardhat node ​

Creates a local ethereum network that stays alive until killed by CTRL + C.

Hardhat for VS Code ​

An extension that adds Solidity language support and provides editor integration for Hardhat-based projects.

console.log ​

Solidity doesn't have any console.log equivalent out-of-the-box. Hardhat fills that void with an implementation:

solidity
import "hardhat/console.sol";

constructor() {
    console.log("Here I am!");
}