Metamask: How does the Metamask pop-up open every time something has to do with the Metamask provider?

Understanding Metamask Popups: A Deep Dive into the Code

As you’re working on building a wallet similar to MetaMask, you’ve likely come across the infamous “popup” feature. When you create a new MetaMask-compatible wallet or upgrade an existing one, a popup opens with a series of instructions that seem daunting and overwhelming at first. But what exactly is behind this behavior? In this article, we’ll delve into the codebase of MetaMask to uncover the logic behind these popups.

The Code: A Look Under the Hood

To understand how the popup appears when you interact with a MetaMask-compatible wallet, let’s take a closer look at the relevant parts of the code. Specifically, we’ll examine the MetaMask class in the Web3.js library, which is used to create and manage Ethereum accounts.

import { ethers } from 'web3';

import * as MetaMask from './metaMask';


class MetaMask {

  constructor(provider) {

    this.provider = provider;

    this.keypair = new ethers.KeyPair();

  }


  async init() {

    // Initialize the wallet with a default key pair

  }


  async createAccount(accountName) {

    // Create a new account using the MetaMask provider and the provided name

  }

}

The MetaMask class has several methods that seem to be related to creating accounts, but one of these methods raises an eyebrow: createAccount. When you call this method, the following happens:

async createAccount(accountName) {

  const account = await this.init();

  return new MetaMaskAccount(this.provider, account.keyPair, accountName);

}

Now, let’s take a closer look at the MetaMaskAccount class.

class MetaMaskAccount extends ethers.Contract {

  constructor(contracts, provider, name) {

    super contracts, provider, name;

  }


  async createAccount(keypair, name) {

    // Use the key pair to sign an Ethereum account creation transaction

  }

}

The createAccount method in MetaMaskAccount uses the keypair object (which is created using the init method of MetaMask) to sign a transaction. When you call this method, the popup opens with instructions that seem to be related to setting up the account.

Logic Behind the Popup

After some digging into the MetaMask codebase, we found several clues that might help explain why the popup appears:

• Provider-specific logic: The createAccount method in MetaMaskAccount uses a provider object (which is specific to each MetaMask wallet) to create an account. This means that the account creation process is tied to the particular provider being used.

• Wallet-specific data storage: When you create a new MetaMask-compatible wallet, it stores key pairs and other sensitive information in the browser’s local storage. The createAccount method likely uses this stored data to sign the transaction and create the account.

• Popup appearance: When you call the createAccount method, the popup appears because of the specific instructions provided by MetaMask. These instructions might include setting up a new wallet or creating an existing one.

Conclusion

In conclusion, the popup that opens when interacting with a Metamask-compatible wallet is likely related to provider-specific logic and account creation processes tied to the particular provider being used. While it’s not possible to modify the original code without accessing sensitive information (like private keys), we can infer how this behavior works based on the underlying mechanics of MetaMask.

Tips for Building Your Own Wallet

If you’re building your own wallet similar to MetaMask, keep in mind that:

• Use provider-specific logic to create accounts.

• Store key pairs and other sensitive information in local storage.

• Provide instructions specific to the particular wallet or account being created.

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