Debugging ERC4337 UserOps using Tenderly

Summary

This video explains how to debug common errors in DApp integration with Bonomi using Tenderly. The tutorial walks through a smart contract example where a failed transaction occurs due to not sending enough ether. By simulating the transaction in Tenderly and decoding the call data, developers can diagnose the exact cause of failure. The video also covers how to handle user operations (User Ops) and resolve common issues like invalid nonces or signature errors. Finally, it highlights the troubleshooting page in Bonomi’s documentation, offering solutions to frequent errors faced during integration.

Takeaways

• 😀 Understanding how to debug Bonomi errors using Tenderly is essential for efficient troubleshooting in DApp integrations.
• 😀 When integrating Bonomi, common errors can occur, such as transaction failures due to missing conditions like sending sufficient ether.
• 😀 The provided contract has a `require` statement that fails when less than 1 ether is sent for an `incrementCount` function, which is the focus of this debugging demo.
• 😀 In Tenderly, decoding call data is crucial to identify the exact reason behind a failed transaction, like missing ether in this case.
• 😀 The simulation of transactions in Tenderly involves entering raw input data and the correct contract address to investigate failure reasons.
• 😀 A common error in Bonomi integrations is the invalid nonce (AA25). This happens when the nonce in a user operation is not updated correctly.
• 😀 The user operation object (user op) is a key component for simulating transaction failures, allowing developers to test different scenarios.
• 😀 Ensure that the `from` address is correctly set as the EntryPoint contract address, not the smart account address when simulating transactions in Tenderly.
• 😀 Errors like 'Sender Already Constructed' (AA1) occur when the init code is modified after deployment, and need to be avoided during simulation.
• 😀 Signature mismatches can lead to 'AA24 Signature Error', a common issue when the signature used in a user operation is incorrect.
• 😀 Bonomi’s documentation includes a troubleshooting page listing common errors, making it a useful resource for developers to quickly resolve issues.
• 😀 For complex issues, reaching out to Bonomi's support team via Discord or Telegram is recommended for additional assistance.

Q & A

What is the purpose of the video?

The video demonstrates how to debug common errors when integrating Bonomi into decentralized applications (DApps) using Tenderly, focusing on transaction failures and user operation issues.

What is the specific issue being tested in the demo contract?

The demo contract includes a require statement that ensures a minimum of 1 ether must be sent to increment a counter. The test involves sending 0.5 ether, which should trigger a failure due to the require condition.

What happens when the transaction fails in this case?

When the transaction fails, the success status of the transaction is marked as 'false'. The reason for the failure is tied to the contract's require statement, which ensures that at least 1 ether is sent.

How can Tenderly be used to debug transaction failures?

Tenderly can be used by decoding the input data and simulating the transaction in their simulator to identify the specific reason for failure, such as a failed require statement or incorrect parameters.

What is the role of call data in debugging with Tenderly?

Call data is essential in debugging because it provides the necessary transaction details, such as the smart contract address and other input parameters, which can be used to simulate and understand why the transaction failed.

What is a user operation (user op), and why is it important for debugging?

A user operation (user op) contains transaction details such as the sender's address, nonce, and other fields. It is important for debugging because issues like incorrect nonces, gas limits, or signatures can cause transaction failures, and these can be identified in the user op object.

What common error occurs when the nonce in a user op is incorrect?

A common error is the 'AA25 invalid account nonce' error, which occurs when the nonce in a user op is one or more units lower than the expected nonce, causing the transaction to fail.

How can the nonce error be fixed when debugging with Tenderly?

To fix the nonce error, the correct nonce value must be retrieved and used in the user op. This ensures that the nonce in the transaction matches the current state of the account.

What happens if the init code in the user op is altered incorrectly?

If the init code in the user op is altered incorrectly, Tenderly will throw an 'AA1 sender already constructed' error, indicating that the contract has already been deployed and cannot be re-initialized with different code.

What should developers do if they encounter common errors during Bonomi integration?

Developers should consult the troubleshooting section in Bonomi's documentation, which lists common errors and their resolutions. Additionally, they can reach out to the Bonomi team on Discord or Telegram for support.