Metamask: Getting execution reverted: ERC20: transfer amount exceeds allowance code: UNPREDICTABLE_GAS_LIMIT method

Metamask: Reverting Execution in Hardhat with Uncertainty

As a developer building decentralized applications (dApps) using Smart Contracts, you’re likely familiar with the importance of ensuring secure and reliable interactions between your application and external services. However, sometimes unexpected issues can arise when interacting with external Swap Functions, causing execution to be reverted.

In this article, we’ll delve into the specifics of the issue and provide guidance on how to resolve it using a combination of Metamask and Hardhat’s TypeScript configuration.

ERC20 Transfer Amount Exceeding Allowance

The first step in troubleshooting is to understand the underlying cause of the error. The message “execution reverted: ERC20: transfer amount exceeds allowance” indicates that the external Swap Function has rejected your request due to an insufficient allowance or transfer amount. This can happen when:

• The recipient’s wallet doesn’t have sufficient Ether (ETH) in their balance.

• The transaction amount is greater than what the recipient can afford.

• There are issues with the allowance property of the token or the transfer function being called.

Metamask: Reverting Execution

To revert the execution and resolve this issue, you’ll need to modify your contract’s logic to handle cases where transfer amounts exceed allowances. One approach is to use Metamask’s built-in support for specifying gas limits in swap functions.

Here’s an example of how you can modify your contract:

import { ethers } from 'ethers';


const MAX_TRANSFER_AMOUNT = 10000000; // ETH


export async function swap(amount: number) {

    const allowance = await contract allowances.call();

    if (allowance.value < MAX_TRANSFER_AMOUNT) {

        console.log('Reverting execution due to insufficient allowance:', amount);

        return;

    }


    const gasLimit = await contract.getAllowanceGasLimit();

    if (gasLimit.value <= 20000) { // Hardcoding the gas limit

        throw new Error('Gas limit is too low');

    }


    try {

        const tx = await contract.swap(amount, allowance.value - amount);

        console.log('Swap transaction executed successfully:', tx.hash);


        // ... Rest of your swap function code ...

    } catch (error) {

        if (error instanceof ethers.AgreedError || error.status === 0x80000000) { // Execution reverted

            console.log('Execution reverted due to gas limit issue:', error.message);

            throw error;

        }

    }

}


export async function main() {

    await contract.deploy();

}

In this example, we’re checking if the allowance value is less than MAX_TRANSFER_AMOUNT before calling the swap function. If not, we revert execution and log a message.

Hardhat Configuration

To enable gas limit support in your Hardhat configuration, you can use the following TypeScript code snippet:

import { HardhatRuntimeEnvironment } from 'hardhat-typescript';

import { Web3Provider } from '@metamask/web3-provider';


export default function config({ network }) {

    return {

        // ... other configuration settings ...

        gasLimit: 20000, // Gas limit for the swap function

    };

}

Conclusion

By understanding the underlying cause of the “execution reverted” error and implementing a solution that handles transfer amounts exceeding allowances using Metamask’s built-in support for specifying gas limits in Swap Functions, you can ensure secure and reliable interactions between your application and external services. Always prioritize testing and debugging to prevent issues from arising.

If you’re experiencing persistent errors or need further assistance, consider reaching out to the Ethereum community or seeking guidance from experienced developers in your network.