Metamask: Solidity query works in dev environment but not in production build (nextJS)

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Metamask: Solidity Queries Work in Dev Environment but Not in Production Build

As a Next.js developer, you’re likely familiar with interacting with decentralized applications (dApps) using Web3 APIs. One of the most popular ways to interact with dApps is through the Metamask wallet, which provides seamless integration between your browser and blockchain networks.

In this article, we’ll explore an issue that can arise when using Metamask with Solidity queries in a Next.js production build environment. We’ll also provide troubleshooting steps and insights into why such issues might occur.

Background

Metamask is a popular wallet for Ethereum-based dApps, allowing users to store, send, receive, and manage their assets. It provides an interface to interact with blockchain networks using Web3 APIs, including the Solidity programming language.

To query the token balance of a user in a Solidity function, you would typically use the eth_call method from the Ethers.js library or Metamask’s eth_sendTransaction method. Both methods allow for sending transactions to Ethereum nodes and retrieving data about the transaction status.

Issue in Production Build

Unfortunately, when we run our Next.js app in production mode, the Solidity queries performed by Metamask fail to execute correctly. This might seem counterintuitive, as we’ve optimized the code to work seamlessly on the dev environment.

Here’s an example of what happens when we call a function that queries the token balance:

import { ethers } from "ethers";


const contractAddress = "0x..."; // replace with your contract address

const userAddress = "0x..."; // replace with your user address


async function getBalance() {

  try {

    const result = await contractAddress.methods.balanceOf(userAddress).call();

    console.log(result);

  } catch (error) {

    console.error(error);

  }

}

In the dev environment, this code executes without issues and returns the expected balance of the user. However, when we run our app in production mode using Next.js, the getBalance function fails to retrieve the balance.

Debugging the Issue

To troubleshoot the issue, let’s analyze what might be going wrong:

• Environment-specific code

  : The key difference between dev and prod environments lies in the environment variables and configurations that are used by Metamask.

• Transaction processing

  : In the production build, the getBalance function is executed on a different Ethereum node than the one used in the dev environment. This might lead to incorrect transaction processing or missing data due to differences in network topology.

• Error handling: The error handling mechanism of Metamask differs between dev and prod environments.

Solution

To resolve this issue, we need to modify our code to handle errors more robustly when running in production mode. Here’s a potential solution:

import { ethers } from "ethers";


const contractAddress = "0x..."; // replace with your contract address

const userAddress = "0x..."; // replace with your user address


async function getBalance() {

  try {

    const result = await contractAddress.methods.balanceOf(userAddress).call();

    console.log(result);

  } catch (error) {

    if (error instanceof ethers.WalletError || error.code === 'E431') {

      console.error("Metamask wallet is not initialized.");

    } else {

      throw error;

    }

  }

}

In this modified code, we added a try-catch block that checks for the following conditions:

• ethers.WalletError: indicates a wallet-related issue.

• E431: occurs when a transaction fails to sign using Ethereum’s default wallet.