[SDK] <Title> Javascript SDK: Unable to use testnet paymaster contract, always paid by ETH

[enochSatis]

Environment

Testnet

Acknowledgement

• I understand that issues are expected with the Go SDK as they are being updated.

Issue Description

Background setting

I am following the tutorial for using the testnet paymaster with Javascript SDK: https://era.zksync.io/docs/dev/building-on-zksync/hello-world.html#paying-fees-using-testnet-paymaster

And also the example codes on gitHub: https://github.com/matter-labs/paymaster-examples/blob/main/contracts/test/erc20fixed.test.ts

I have deployed the demo Greeter.sol at 0x88Be52128A0CE7ed65c845c888bf2FFD69Aa271c, and I would like to trigger the contract with the testnet paymaster.

My procedure

1. I get the testnet paymaster address with: provider.getTestnetPaymasterAddress(). The return is 0x8f0ea1312da29f17eabeb2f484fd3c112cccdd63 which seems correct.
2. I choose to pay with the testnet DAI, so I picked the token address 0x3e7676937A7E96CFB7616f255b9AD9FF47363D4b, which should also be correct.
3. I set the paymaster estimation parameters according to the tutorial:

const paymasterEstimateParams = utils.getPaymasterParams(paymasterAddress, {
    type: "ApprovalBased",
    token: "0x3e7676937A7E96CFB7616f255b9AD9FF47363D4b",
    minimalAllowance: ethers.BigNumber.from(1),
    innerInput: new Uint8Array(),
});

4. Then I setup the paymaster parameters according to the tutorial:

const fee = gasPrice.mul(gasLimit.toString());
const paymasterParams = utils.getPaymasterParams(paymasterAddress, {
    type: "ApprovalBased",
    token: "0x3e7676937A7E96CFB7616f255b9AD9FF47363D4b",
    minimalAllowance: fee,
    // empty bytes as testnet paymaster does not use innerInput
    innerInput: new Uint8Array(),
});

5. Finally plugging the paymaster parameters into the contract interaction transaction:

const tx = await contract.setGreeting(newMessage, {
    maxFeePerGas: gasPrice,
    maxPriorityFeePerGas: ethers.BigNumber.from(0),
    gasLimit: gasLimit,
    customData: {
      gasPerPubdata: utils.DEFAULT_GAS_PER_PUBDATA_LIMIT,
      paymasterParams
    },
});

Problem

No matter how I tried, the transaction will success but the gas is always paid with ETH.

Expected Behavior

I tried the following modifications, but the transaction will always be paid with ETH:

1. Try using paymaster with and without approving the token to the testnet paymaster contract.
2. Toggling the paymasterParams field in the customData:

customData: {
    gasPerPubdata: utils.DEFAULT_GAS_PER_PUBDATA_LIMIT,
    paymasterParams,
    // paymasterParams: paymasterParams,
},

3. Using the paymasterEstimationParams (with minimalAllowance: ethers.BigNumber.from(1) as some other examples suggest)

Code Example

My code is a modification of the demo use-greeter.ts. I have hardcoded the addresses except for the wallet private key, so anyone can run this directly.

use-greeter.ts

import { Provider, utils } from "zksync-web3";
import * as ethers from "ethers";
import { HardhatRuntimeEnvironment } from "hardhat/types";

// load env file
import dotenv from "dotenv";
dotenv.config();

// load contract artifact. Make sure to compile first!
import * as ContractArtifact from "../artifacts-zk/contracts/Greeter.sol/Greeter.json";

const PRIVATE_KEY = process.env.WALLET_PRIVATE_KEY || "";

// Pay in DAI on testnet
const PAYMASTER_TOKEN_ADDR = "0x3e7676937A7E96CFB7616f255b9AD9FF47363D4b";
console.log(`Paymaster token address: ${PAYMASTER_TOKEN_ADDR}`);

if (!PRIVATE_KEY)
  throw "⛔️ Private key not detected! Add it to the .env file!";

// Address of the contract on zksync testnet
const CONTRACT_ADDRESS = "0x88Be52128A0CE7ed65c845c888bf2FFD69Aa271c";

if (!CONTRACT_ADDRESS) throw "⛔️ Contract address not provided";

// An example of a deploy script that will deploy and call a simple contract.
export default async function (hre: HardhatRuntimeEnvironment) {

  console.log(`Running script to interact with contract ${CONTRACT_ADDRESS}`);

  // Initialize the provider.
  // @ts-ignore
  const provider = new Provider(hre.userConfig.networks?.zkSyncTestnet?.url);
  const signer = new ethers.Wallet(PRIVATE_KEY, provider);

  var paymasterAddress = await provider.getTestnetPaymasterAddress();
  paymasterAddress = String(paymasterAddress);
  console.log(`Testnet paymaster address: ${paymasterAddress}`);


  const paymasterEstimateParams = utils.getPaymasterParams(paymasterAddress, {
    type: "ApprovalBased",
    token: PAYMASTER_TOKEN_ADDR,
    minimalAllowance: ethers.BigNumber.from(1),
    innerInput: new Uint8Array(),
  });

  // Initialize contract instance
  const contract = new ethers.Contract(
    CONTRACT_ADDRESS,
    ContractArtifact.abi,
    signer
  );

  // Read message from contract
  console.log(`The message is ${await contract.greet()}`);

  // send transaction to update the message
  const newMessage = "Greetings Programs!";

  const gasPrice = await provider.getGasPrice();
  const gasLimit = await contract.estimateGas.setGreeting(newMessage, {
    customData: {
      gasPerPubdata: utils.DEFAULT_GAS_PER_PUBDATA_LIMIT,
      // paymasterParams: paymasterEstimateParams,
      paymasterEstimateParams,
    },
  });
  console.log(`Gas price: ${gasPrice}`);
  console.log(`Gas limit: ${gasLimit}`);

  const fee = gasPrice.mul(gasLimit.toString());
  console.log(`Fee: ${fee}`);



  const paymasterParams = utils.getPaymasterParams(paymasterAddress, {
    type: "ApprovalBased",
    token: PAYMASTER_TOKEN_ADDR,
    minimalAllowance: fee,
    // empty bytes as testnet paymaster does not use innerInput
    innerInput: new Uint8Array(),
  });

  const tx = await contract.setGreeting(newMessage, {
    maxFeePerGas: gasPrice,
    maxPriorityFeePerGas: ethers.BigNumber.from(0),
    gasLimit: gasLimit,
    customData: {
      gasPerPubdata: utils.DEFAULT_GAS_PER_PUBDATA_LIMIT,
      // paymasterParams: paymasterParams,
      paymasterParams
    },
  });
  console.log(`Transaction to change the message is ${tx.hash}`);
  await tx.wait();

  // Read message after transaction
  console.log(`The message now is ${await contract.greet()}`);
}

package.json

{
  "name": "zksync-hardhat-template",
  "version": "1.0.0",
  "main": "index.js",
  "author": "Antonio <[email protected]>",
  "license": "MIT",
  "devDependencies": {
    "@matterlabs/hardhat-zksync-deploy": "^0.6.5",
    "@matterlabs/hardhat-zksync-solc": "^0.4.2",
    "@matterlabs/hardhat-zksync-verify": "^0.1.8",
    "@matterlabs/zksync-contracts": "^0.6.1",
    "@nomiclabs/hardhat-etherscan": "^3.1.7",
    "@openzeppelin/contracts": "^4.9.3",
    "@types/chai": "^4.3.4",
    "@types/mocha": "^10.0.1",
    "chai": "^4.3.7",
    "dotenv": "^16.0.3",
    "ethers": "^5.7.2",
    "hardhat": "^2.12.4",
    "mocha": "^10.2.0",
    "ts-node": "^10.9.1",
    "typescript": "^4.9.4",
    "zksync-web3": "^0.14.3"
  },
  "scripts": {
    "test": "NODE_ENV=test hardhat test --network zkSyncTestnet",
    "deploy": "yarn hardhat deploy-zksync --script deploy-greeter.ts",
    "greet": "yarn hardhat deploy-zksync --script use-greeter.ts"
  }
}

Repo Link (Optional)

No response

[dutterbutter]

Thanks for the very well documented issue. The setup looks correct at first glance, what rpc are you connecting to in your hardhat config (e.g. hre.userConfig.networks?.zkSyncTestnet?.url)? Also what wallet are you using?

[enochSatis]

@dutterbutter Hi is there any update on this issue?

[dutterbutter]

Hey @enochSatis I can't seem to determine the root cause here. The Hello world example that makes use of the testnet paymaster works fine and successfully pays fees using DAI. I have deployed other paymasters to testnet using the approval based flow to pay fees in DAI and USDC and that works fine as well.

We do intend to deprecate the testnet paymaster as it was an effort to showcase the capabilities initially. I apologize for the inconvenience here and will follow up if I do discover the root cause.

[enochSatis]

Got it. I will try to deploy my own paymaster contract and try again. Thanks for your help.

[dutterbutter]

@enochSatis actually I see the issue! I was able to successfully run this and pay with DAI.

The issue is you are using ethers.Wallet rather than the our sdks Wallet. So try this:

import { Provider, utils, Wallet } from "zksync-web3";
import * as ethers from "ethers";
import { HardhatRuntimeEnvironment } from "hardhat/types";

// load env file
import dotenv from "dotenv";
dotenv.config();

// load contract artifact. Make sure to compile first!
import * as ContractArtifact from "../artifacts-zk/contracts/Greeter.sol/Greeter.json";

const PRIVATE_KEY = process.env.WALLET_PRIV_KEY || "";

// Pay in DAI on testnet
const PAYMASTER_TOKEN_ADDR = "0x3e7676937A7E96CFB7616f255b9AD9FF47363D4b";
console.log(`Paymaster token address: ${PAYMASTER_TOKEN_ADDR}`);

if (!PRIVATE_KEY)
  throw "⛔️ Private key not detected! Add it to the .env file!";

// Address of the contract on zksync testnet
const CONTRACT_ADDRESS = "0x88Be52128A0CE7ed65c845c888bf2FFD69Aa271c";

if (!CONTRACT_ADDRESS) throw "⛔️ Contract address not provided";

// An example of a deploy script that will deploy and call a simple contract.
export default async function (hre: HardhatRuntimeEnvironment) {

  console.log(`Running script to interact with contract ${CONTRACT_ADDRESS}`);

  // Initialize the provider.
  // @ts-ignore
  const provider = new Provider(hre.userConfig.networks?.zkSyncTestnet?.url);
  const signer = new Wallet(PRIVATE_KEY, provider);

  var paymasterAddress = await provider.getTestnetPaymasterAddress();
  paymasterAddress = String(paymasterAddress);
  console.log(`Testnet paymaster address: ${paymasterAddress}`);


  const paymasterEstimateParams = utils.getPaymasterParams(paymasterAddress, {
    type: "ApprovalBased",
    token: PAYMASTER_TOKEN_ADDR,
    minimalAllowance: ethers.BigNumber.from(1),
    innerInput: new Uint8Array(),
  });

  // Initialize contract instance
  const contract = new ethers.Contract(
    CONTRACT_ADDRESS,
    ContractArtifact.abi,
    signer
  );

  // Read message from contract
  console.log(`The message is ${await contract.greet()}`);

  // send transaction to update the message
  const newMessage = "Greetings Programs!";

  const gasPrice = await provider.getGasPrice();
  const gasLimit = await contract.estimateGas.setGreeting(newMessage, {
    customData: {
      gasPerPubdata: utils.DEFAULT_GAS_PER_PUBDATA_LIMIT,
      // paymasterParams: paymasterEstimateParams,
      paymasterEstimateParams,
    },
  });
  console.log(`Gas price: ${gasPrice}`);
  console.log(`Gas limit: ${gasLimit}`);

  const fee = gasPrice.mul(gasLimit.toString());
  console.log(`Fee: ${fee}`);

  const paymasterParams = utils.getPaymasterParams(paymasterAddress, {
    type: "ApprovalBased",
    token: PAYMASTER_TOKEN_ADDR,
    minimalAllowance: fee,
    // empty bytes as testnet paymaster does not use innerInput
    innerInput: new Uint8Array(),
  });

  const tx = await contract.connect(signer).setGreeting(newMessage, {
    maxFeePerGas: gasPrice,
    maxPriorityFeePerGas: ethers.BigNumber.from(0),
    gasLimit: gasLimit,
    customData: {
      gasPerPubdata: utils.DEFAULT_GAS_PER_PUBDATA_LIMIT,
      // paymasterParams: paymasterParams,
      paymasterParams
    },
  });
  console.log(`Transaction to change the message is ${tx.hash}`);
  await tx.wait();

  // Read message after transaction
  console.log(`The message now is ${await contract.greet()}`);
}

And let me know if that works for you. You will notice we are using Wallet from zksync-web3 and connecting to when doing the setGreeter call.

[enochSatis]

I see! Thanks for your help!