Metamask: function selector not found in hardhat node

Here is an article that explains the issue you’re facing with Metamask’s function selector not found error when calling a smart contract from your ReactJS application:

Metamask Function Selector Not Found Error

When developing decentralized applications (dApps), it’s common to interact with Ethereum-based contracts using Web3 libraries like Ethers.js. However, one common issue that can arise is the “function selector not found” error in Hardhat node.

In this article, we’ll delve into what causes this error and how you can resolve it when calling a smart contract from your ReactJS application using Metamask.

What is Metamask?

Metamask is an Ethereum wallet that allows users to interact with the Ethereum blockchain. It provides a user-friendly interface for managing private keys, sending transactions, and accessing various functionality of the Ethereum network.

Function Selector Not Found Error in Hardhat Node

When you’re using Hardhat node to compile and deploy smart contracts, Metamask needs to know which function selector to use to interact with the contract. However, if this information is not provided or is incorrect, you’ll encounter a “function selector not found” error.

Here’s an example of what might go wrong:

import { compile } from 'hardhat-typescript';


const compileContract = async (contractName, ABI) => {

  try {

    const contract = await compile(contractName);

    const binascii = Buffer.from(ABI.map((key) => key.type).join(','));

    const selector = '0x' + binascii;

    console.log(selector); // This should be the correct function selector


    // Now, you're calling the contract with this selector

    await contract.at(selector).call('getTokenDepositAmount', inputToken);

  } catch (error) {

    console.error(error);

  }

};

In this example, selector is a hexadecimal string that represents the Ethereum bytecode for the function getTokenDepositAmount. The at() method of the contract object returns a new contract with the specified selector. However, if you’re using a smart contract from Metamask’s collection, like the “SushiSwap” contract, it will have a different bytecode.

What goes wrong when using Metamask?

There are several reasons why you might encounter a “function selector not found” error:

• Incorrect ABI: If your smart contract’s ABI is incorrect or missing certain functions, Metamask won’t be able to determine the correct function selector.

• Metamask collection: When using a smart contract from Metamask’s collection (e.g., SushiSwap), you need to specify the correct bytecode in the compileContract function.

• Hardhat configuration: Your Hardhat project might not have the necessary configuration settings or dependencies to properly compile and deploy your smart contracts.

Resolving the issue

To resolve this error, ensure that:

• You’ve correctly compiled and deployed your smart contract using a tool like Truffle or Vyper.

• Your Metamask collection is set up correctly and includes all required functions (e.g., getTokenDepositAmount).

• Your Hardhat project has the necessary dependencies and configuration settings.

Here’s an updated example that uses SushiSwap’s contract:

“`javascript

import { compileContract } from ‘hardhat-typescript’;

import ‘@nomiclabs/hardhat-waffle’;

const compile = async (contractName, ABI) => {

try {

const contract = await compile(contractName);

const binascii = Buffer.from(ABI.map((key) => key.type).join(‘,’));

const selector = ‘0x’ + binascii;

// Now, you’re calling the contract with this selector

return await contract.at(selector).call(‘getTokenDepositAmount’, inputToken);

} catch (error) {

console.