Script to send an EIP712 transaction via paymaster on ZKsync using Remix

ZKsync Remix paymaster transaction

import * as ethers from "ethers";
import {Provider, Contract, utils, Signer, BrowserProvider, Wallet} from "zksync-ethers";

// Address of the ZeekMessages contract
const GREETER_CONTRACT_ADDRESS = "0x2f5Fa95a28EEd40DD80ED3fFC718094EB41253b4";
// Address of the ERC20 token contract
const TOKEN_CONTRACT_ADDRESS = "0xF4dF2c515581A9fA5bAa078d04703c0f3Fd9115a";
// Message to be sent to the contract
const NEW_MESSAGE = "This tx cost me no ETH!";

const GREETER_ABI = [
  {
    "inputs": [],
    "name": "greet",
    "outputs": [{ "internalType": "string", "name": "", "type": "string" }],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [{ "internalType": "string", "name": "_greeting", "type": "string" }],
    "name": "setGreeting",
    "outputs": [],
    "stateMutability": "nonpayable",
    "type": "function"
  }
];

(async () => {
  try {

  console.log('Sending a transaction via the testnet paymaster')

  const browserProvider = new ethers.BrowserProvider(web3Provider)
  const signer = await browserProvider.getSigner()

  console.log("Signer:", await signer.getAddress());

  const zkProvider = new Provider("https://sepolia.era.zksync.dev");
  const zkBrowserProvider = new BrowserProvider(web3Provider);

  const chainId = Number((await browserProvider.getNetwork()).chainId)
  console.log("chain id >> ", chainId)
 

  const zkSigner = Signer.from(await zkBrowserProvider.getSigner(), chainId, zkProvider);
//   const zkSigner = Signer.from(signer, , zkProvider);

  console.log(`ZK Signer ${await zkSigner.getAddress()}`)

  const testnetPaymasterAddress = await zkProvider.getTestnetPaymasterAddress()
  console.log(`Testnet paymaster address is ${testnetPaymasterAddress}`);

  const gasPrice = await zkProvider.getGasPrice();

  console.log("gasPrice is >> ", gasPrice)

  // initialise messages and token contracts with address, abi and signer
  const messagesContract= new Contract(GREETER_CONTRACT_ADDRESS, GREETER_ABI, zkSigner);

  // define paymaster parameters for gas estimation
  const paramsForFeeEstimation = utils.getPaymasterParams(testnetPaymasterAddress, {
    type: "ApprovalBased",
    token: TOKEN_CONTRACT_ADDRESS,
    // set minimalAllowance to 1 for estimation
    minimalAllowance: 1n,
    // empty bytes as testnet paymaster does not use innerInput
    innerInput: new Uint8Array(0),
  });

  console.log(paramsForFeeEstimation)

  // estimate gasLimit via paymaster
  const gasLimit = await messagesContract.setGreeting.estimateGas(NEW_MESSAGE, {
    customData: {
      gasPerPubdata: utils.DEFAULT_GAS_PER_PUBDATA_LIMIT,
      paymasterParams: paramsForFeeEstimation,
    },
  });

  console.log("gasLimit is >> ", gasLimit)


  // fee calculated in ETH will be the same in
  // ERC20 token using the testnet paymaster
  const fee = gasPrice * gasLimit;

  console.log("Fee is >>", fee);

  // new paymaster params with fee as minimalAllowance
  const paymasterParams = utils.getPaymasterParams(testnetPaymasterAddress, {
    type: "ApprovalBased",
    token: TOKEN_CONTRACT_ADDRESS,
    // provide estimated fee as allowance
    minimalAllowance: fee,
    // minimalAllowance: 1n,
    // empty bytes as testnet paymaster does not use innerInput
    innerInput: new Uint8Array(0),
  });

  // full overrides object including maxFeePerGas and maxPriorityFeePerGas
  const txOverrides = {
    maxFeePerGas: gasPrice,
    maxPriorityFeePerGas: "1",
    // hardcoded
    // gasLimit: 600000,
    gasLimit,
    customData: {
      gasPerPubdata: utils.DEFAULT_GAS_PER_PUBDATA_LIMIT,
      paymasterParams,
    }
  }

  console.log(`Sending tx via your wallet`);

  // send transaction with additional paymaster params as overrides
  const txHandle = await messagesContract.setGreeting(NEW_MESSAGE, txOverrides);
  await txHandle.wait();
  console.log(`Transaction processed`)
  

  console.log(`Done!`);

  } catch (e) {
    console.error('Error in script!')
    console.error(e.message)
    console.error(e)
  }
})()