Language: English

Author: Dustin

Level: Beginner

Introduction to Hardhat Polkadot 🚀

This guide helps you set up a development environment to deploy Solidity smart contracts on Polkadot's PolkaVM using the Hardhat Polkadot plugin, covering project setup to ERC20 deployment on Paseo Asset Hub.

What is Hardhat Polkadot?

• What it is: A plugin for Hardhat, the Ethereum development environment.
• Purpose: Extends Hardhat's capabilities for Polkadot.
• Key Functions:
  • Compile Solidity smart contracts.
  • Deploy Solidity smart contracts.
  • Test Solidity smart contracts.
• Target: Polkadot parachains that utilize PolkaVM (a RISC-V based virtual machine).
• Benefit: Provides a familiar development workflow for existing EVM developers within the Polkadot ecosystem.

1. Project Setup and Installation 🛠️

First, let's create a new project directory and initialize it.

1. Create and navigate into your project folder:

   mkdir hardhat-example
   cd hardhat-example
   

2. Initialize a Node.js project:

   npm init -y
   

3. Install the Hardhat Polkadot plugin:

   npm install --save-dev @parity/hardhat-polkadot@0.1.5
   

4. Initialize a Hardhat Polkadot project:

   npx hardhat-polkadot init
   

   You will be prompted to choose a project type. For this guide, select Create a JavaScript project.

   📝 Important Note: When the installer asks: Do you want to install this sample project's dependencies with npm (@nomicfoundation/hardhat-toolbox)?

   Choose n (No). We will install the required dependency manually in a later step to ensure compatibility.

5. Install dotenv to manage environment variables:

   npm i dotenv@16.5.0
   

2. Hardhat Configuration ⚙️

Now, let's configure Hardhat to connect to the Paseo Asset Hub and enable PolkaVM.

1. Open the hardhat.config.js file and replace its contents with the following configuration.

   Key Point: The polkavm: true flag is essential. It tells the Hardhat Polkadot plugin to compile and deploy the contract for the PolkaVM environment.

   require('@nomicfoundation/hardhat-toolbox');
   require('@parity/hardhat-polkadot');
   require('dotenv').config();
   /** @type import('hardhat/config').HardhatUserConfig */
   module.exports = {
       solidity: '0.8.28',
       resolc: {
           compilerSource: 'npm',
       },
       networks: {
           hardhat: {
               polkavm: true,
               forking: {
                   url: 'wss://westend-asset-hub-rpc.polkadot.io',
               },
               adapterConfig: {
                   adapterBinaryPath: './bin/eth-rpc',
                   dev: true,
               },
           },
           // add paseo asset hub network 
           paseo: {
               polkavm: true,
               url: 'https://testnet-passet-hub-eth-rpc.polkadot.io/',
               accounts: [process.env.PASEO_PK],
           },
       }
   };
   

2. Create a .env file in your project's root directory to store your private key securely.

   touch .env
   

3. Add your account's private key to the .env file.

   PASEO_PK=<your_private_key_here>
   

   💰 Get Testnet Funds: Make sure your account has a sufficient balance. You can get free testnet tokens from the official Polkadot faucet: Faucet

3. Deploy ERC20 on Paseo Asset Hub 🚢

The initialization process created an example ERC20 contract. Let's compile and deploy it.

Compile the Contract

1. Run the standard Hardhat compile command.

   npx hardhat compile
   

   You will likely encounter the following error:

   An unexpected error occurred:
   
   Error: Cannot find module '@nomicfoundation/hardhat-toolbox'
   Require stack:
   ...
   

2. Fix the Compilation Error This error occurs because the initializer is not yet stable. To fix it, manually install the correct version of @nomicfoundation/hardhat-toolbox.

   💡 Solution: Run the following command to install the necessary dependency. The --force flag may be needed to resolve peer dependency conflicts.

   npm install --save-dev @nomicfoundation/hardhat-toolbox@5.0.0 --force
   

3. Now, run the compile command again. It should complete successfully.

   npx hardhat compile
   

Deploy with Ignition

We will use Hardhat Ignition to deploy our MyToken.sol contract to the Paseo network.

1. Execute the deployment script.

   npx hardhat ignition deploy ignition/modules/MyToken.js --network paseo
   

2. Check the result. A successful deployment will look like this:

   Hardhat Ignition 🚀
   
   Deploying [ MyTokenModule ]
   
   Batch #1
     Executed MyTokenModule#MyToken
   
   [ MyTokenModule ] successfully deployed 🚀
   
   Deployed Addresses
   
   MyTokenModule#MyToken - 0x30d1868A104c74C79694345536b38E4d098C6146
   

3. You can verify your deployed contract on the Paseo Asset Hub block explorer: https://blockscout-passet-hub.parity-testnet.parity.io/token/0x30d1868A104c74C79694345536b38E4d098C6146

4. Interact with the ERC20 Contract 💸

Let's interact with our newly deployed token by transferring some to another address.

1. Create a new script file scripts/transferERC20.js and add the following code. This script reads the deployed contract address, checks the sender's balance, and transfers 100 tokens.

   const { ethers } = require("hardhat");
   const { readFileSync } = require("fs");
   const path = require("path");
   
   async function main() {
   
     const deploymentPath = path.join(
       __dirname,
       "../ignition/deployments/chain-1003/deployed_addresses.json"
     );
   
     const deployment = JSON.parse(readFileSync(deploymentPath, "utf8"));
     const contractAddress = deployment["MyTokenModule#MyToken"];
   
     if (!contractAddress) {
       throw new Error("ERC20 contract address not found in deployment artifact");
     }
   
     const erc20Abi = [
       "function transfer(address to, uint256 amount) public returns (bool)",
       "function balanceOf(address account) public view returns (uint256)",
     ];
   
     const [signer] = await ethers.getSigners();
     console.log("Transferring from account:", signer.address);
   
     const erc20Contract = await ethers.getContractAt(erc20Abi, contractAddress, signer);
   
     const recipientAddress = "0xD08B851df86AD3777239e26016Bc2695817bD86c"; 
     const amount = ethers.parseUnits("100", 18);
   
     const balance = await erc20Contract.balanceOf(signer.address);
     console.log("Sender's balance:", ethers.formatUnits(balance, 18), "tokens");
   
     if (balance < amount) {
       throw new Error("Insufficient balance for transfer");
     }
   
     console.log(`Transferring ${ethers.formatUnits(amount, 18)} tokens to ${recipientAddress}...`);
     const tx = await erc20Contract.transfer(recipientAddress, amount);
     await tx.wait(); 
   
     console.log("Transfer successful! Transaction hash:", tx.hash);
   }
   
   main()
     .then(() => process.exit(0))
     .catch((error) => {
       console.error(error);
       process.exit(1);
     });
   

2. Run the script on the paseo network.

   npx hardhat run scripts/transferERC20.js --network paseo
   

3. The output will confirm the successful transfer.

   Transferring from account: 0x783FC27915754512E72b5811599504eCa458E4C5
   Sender's balance: 1000000.0 tokens
   Transferring 100.0 tokens to 0xD08B851df86AD3777239e26016Bc2695817bD86c...
   Transfer successful! Transaction hash: 0x1e4e265791231ed513cd3fdda2e36e599f9e5c77568bad2bc5f29f507ee1abf8
   

Conclusion ✅

Congratulations! You've successfully deployed Solidity smart contracts on Polkadot's PolkaVM using Hardhat! It's just like EVM development, but with a simple polkavm: true flag, making PolkaVM accessible for all.

Full Source Code: https://github.com/CocDap/introduction-to-hardhat-polkadot