Verify a Smart Contract using the Hardhat Verification Plugin

Smart contracts are the backbone of decentralized applications (dApps). They automate agreements and processes, but their code can be complex and prone to errors. Verifying your smart contracts is crucial to ensure they function as intended.

This tutorial will guide you through verifying your contracts using the Hardhat Verification Plugin on the Rootstock Blockscout Explorer. This plugin simplifies the verification of Solidity smart contracts deployed on the Rootstock network. By verifying the contracts, you allow Blockscout, an open-source block explorer, to link your contract's source code with its deployed bytecode on the blockchain, allowing for more trustless interaction with the code.

In this tutorial, we'll do the following steps:

• Set up your hardhat config environment in your project
• Use the hardhat-verify plugin to verify a contract address.

Prerequisites

To follow this tutorial, you should have knowledge of the following:

• Hardhat
• Basic knowledge of smart contracts

Hardhat Starter dApp

A Hardhat Starter dApp has been created with preset configuration for the Rootstock network. Clone and follow the instructions in the README to setup the project. Note: To set the .env variables to match the hardhat.config.ts file, if using the starter dApp for this tutorial.

What is hardhat-verify?

Hardhat is a full-featured development environment for contract compilation, deployment and verification. The hardhat-verify plugin supports contract verification on the Rootstock Blockscout Explorer.

Note: The hardhat-verify plugin will be available soon on the Rootstock Explorer.

Installation

npm install --save-dev @nomicfoundation/hardhat-verify

And add the following code to your hardhat.config.ts file:

require("@nomicfoundation/hardhat-verify");

Or, if you are using TypeScript, add this to your hardhat.config.ts:

import "@nomicfoundation/hardhat-verify";

Usage

You need to add the following Etherscan config to your hardhat.config.ts file:

// Hardhat configuration
const config: HardhatUserConfig = {
    defaultNetwork: "hardhat",
    networks: {
        hardhat: {
            // If you want to do some forking, uncomment this
            // forking: {
            //   url: MAINNET_RPC_URL
            // }
        },
        localhost: {
            url: "http://127.0.0.1:8545",
        },
        rskMainnet: {
            url: RSK_MAINNET_RPC_URL,
            chainId: 30,
            gasPrice: 60000000,
			accounts:[PRIVATE_KEY]
        },
        rskTestnet: {
            url: RSK_TESTNET_RPC_URL, 
            chainId: 31,
            gasPrice: 60000000,
			accounts:[PRIVATE_KEY]
        },
    },
    namedAccounts: {
        deployer: {
            default: 0, // Default is the first account
            mainnet: 0,
        },
        owner: {
            default: 0,
        },
    },
    solidity: {
        compilers: [
            {
                version: "0.8.24",
            },
        ],
    },
    sourcify: {
        enabled: false
      },      
    etherscan: {    
        apiKey: {
          // Is not required by blockscout. Can be any non-empty string
          rskTestnet: 'RSK_TESTNET_RPC_URL',
          rskMainnet: 'RSK_MAINNET_RPC_URL'
        },
        customChains: [
          {
            network: "rskTestnet",
            chainId: 31,
            urls: {
              apiURL: "https://rootstock-testnet.blockscout.com/api/",
              browserURL: "https://rootstock-testnet.blockscout.com/",
            }
          },
          {
            network: "rskMainnet",
            chainId: 30,
            urls: {
              apiURL: "https://rootstock.blockscout.com/api/",
              browserURL: "https://rootstock.blockscout.com/",
            }
          },

        ]
      },
};

export default config;

Now, run the verify task, passing the address of the contract, the network where it's deployed, and any other arguments that was used to deploy the contract:

npx hardhat verify --network rskTestnet DEPLOYED_CONTRACT_ADDRESS

or

npx hardhat verify --network rskMainnet DEPLOYED_CONTRACT_ADDRESS

Tip

• Replace DEPLOYED_CONTRACT_ADDRESS with the contract address.
• This can be gotten from the MockERC721.json file containing the addresses and abi under the deployments/network folder.

The response should look like this:

npx hardhat verify  --network rskTestnet 0x33aC0cc41B11282085ff6db7E1F3C3c757143722 
Successfully submitted source code for contract
contracts/ERC721.sol:MockERC721 at 0x33aC0cc41B11282085ff6db7E1F3C3c757143722
for verification on the block explorer. Waiting for verification result...
Successfully verified contract MockERC721 on the block explorer.
https://rootstock-testnet.blockscout.com/address/0x33aC0cc41B11282085ff6db7E1F3C3c757143722#code

Resources

• Visit hardhat-verify
• Visit blockscout
• Hardhat Starter Kit for Rootstock