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

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Metamask: Solidity requests work in developer environment but not in production

As a Next.js developer, you are probably 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 the browser and blockchain networks.

In this article, we will examine an issue that can occur when using Metamask with Solidity requests in Next.js production environment. We will also provide troubleshooting steps and insights into why such issues may occur.

Background

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

To query a user’s token balance using a Solidity function, you typically use the “eth_call” method from the Ethers.js library or the “eth_sendTransaction” method from Metamask. Both methods allow you to send transactions to Ethereum nodes and get transaction status data.

Issue in production

Unfortunately, when we run the Next.js application in production mode, the Solidity requests made by Metamask are not executed correctly. This may seem counterintuitive, as we have optimized the code to run smoothly in a developer environment.

Here is an example of what happens when we call the 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 development environment, this code runs without any problems and returns the expected user balance. However, when we run the application in production mode using Next.js, the getBalance function fails to retrieve the balance.

Debugging the problem

To fix the problem, analyze what might be wrong:

• Environment-specific code: The main difference between development and production environments is in the environment variables and configurations used by Metamask.

• Transaction processing

  

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

• Error Handling: Metamask’s error handling mechanism is different in the dev and production environments.

Solution

To fix this issue, we need to modify our code to handle errors more reliably when running in production mode. Here is a possible 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 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 the default Ethereum wallet.

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