Deploy a smart contract to Polygon zkEVM Testnet with Hardhat and verify the contract

by Steph aka 0ceans404 on Twitter

Polygon zkEVM is the first zero-knowledge scaling solution that is fully equivalent to an EVM. All existing smart contracts, developer toolings and wallets work seamlessly. Polygon zkEVM harnesses the power of zero-knowledge proofs in order to reduce transaction costs and massively increase throughput, all while inheriting the security of Ethereum.

Here's how to deploy the smart contract in this repo to the Polygon zkEVM Testnet with Hardhat. If you're trying to deploy an existing repo, check out my hardhat.config.js file then follow this repo's Deploy steps starting here

Getting Started

⭐️ Star this repo, then clone it and install dependencies

git clone https://github.com/oceans404/zkevm-hardhat-demo
npm i

Create a .env file

cp .env.sample .env;

Update .env to set your ACCOUNT_PRIVATE_KEY environment variable. Here's an article on how to get your private key from MetaMask.

Code callouts in deploy.js

The base of this project is the default Hardhat Project Lock contract bootstrapped when you select "Create a JavaScript project." I modified the deploy script slightly for easier testing.

lockedAmount: .0007 ETH
unlockTime: 3 minutes
include testnet explorer link in deployment console log statement

Optionally run default hardhat tasks for local development:

npx hardhat help
npx hardhat test
REPORT_GAS=true npx hardhat test
npx hardhat node
npx hardhat run scripts/deploy.js

Deploy to the Polygon zkEVM Testnet

Before you deploy to the Polygon zkEVM Testnet, you need zkEVM Testnet ETH. Watch my bridging video to learn how to bridge Goerli ETH to Polygon zkEVM Testnet ETH.

If you already have Goerli ETH in your account, start the video here.

Once you've funded your account with testnet ETH, run

npx hardhat run scripts/deploy.js --network zkEVM

My result was

Lock with .0007 ETH and unlock timestamp 1677340384 
    
    Deployed to https://explorer.public.zkevm-test.net/address/0xc97d80F068c7Ef0fBBE05eBECD8500427F319b7D

Contract: https://explorer.public.zkevm-test.net/address/0xc97d80F068c7Ef0fBBE05eBECD8500427F319b7D

Verify your Polygon zkEVM Testnet contract

As of today, there are no Polygon zkEVM Testnet explorer API keys, so you have to verify contracts manually.

Find your contract on the Polygon zkEVM Testnet explorer.
Select the "Code" tab.
Click the "Verify and Publish" Button
Verify "Via Standard Input JSON"
Update "Compiler" based on your contract's compiler version

pragma solidity ^0.8.9; => v0.8.9+commit.e5eed63a

In your local repo folder, navigate to the file in the build-info folder. artifacts > build-info > {superlongnumberfile}.json. Save this file to parse it with Prettier. Then find the input JSON object. It will look something like this "input": {}. Copy the input object value into a new file. Name and save this file locally. I saved mine as example-standard-input.json in the root folder so you can check out the format, but use your own file.
Upload this file in the drag and drop "Standard Input JSON" file field.
Since we have an input, set "Try to fetch constructor arguments automatically" to NO.
To add your ABI-encoded instrctor arguments, open the Online ABI Encoder and choose the auto-parse tab.
In your local repo folder, navigate to the file in the build-info folder. artifacts > build-info > {superlongnumberfile}.json. Find your ABI json array "abi": [], and copy/paste the array value into the auto-parse text box. Click "Parse."
You'll see any inputs appear below. We need to specify the _unlockTime input value. We console logged this timestamp in deploy.js and it was 1677340384. Paste it in and you'll see the Encoded Data generated below.
Copy the Encoded Data and use it for "ABI-encoded Constructor Arguments (if required by the contract)" back in the Polygon zkEVM Testnet explorer field.
Click "Verify and Publish." The form will be in loading state. I opened the contract in a new tab and after about 5m I saw a green check mark next to the "Code" tab for verified even though the Loader never updated on the UI.

Here's my verified contact

Read unlock time

Go to the "Read Contract" tab. Here's mine

Withdraw locked funds

Before you withdraw funds you'll need to add the Polygon zkEVM Testnet as a Network within MetaMask so you can connect your account. Watch my video to learn how to add the Polygon zkEVM Testnet to MetaMask in less than 2 minutes.

Go to your "Write Contract" tab. Here's mine

Click "write" next to the withdraw function. You will have to connect to Polygon zkEVM testnet with the same account you used to deploy your smart contract. (The account whose private key you grabbed for the .env file).

If you look at my transactions tab you can see I was able to successfully withdraw the funds I locked while deploying the contract.