Problem

The getProof method in the @openzeppelin/merkle-tree library expects input data in the format consistent with the leaf structure of the Merkle Tree. In the current implementation, the method is called with an array containing the address and value directly:

const proof = merkleTree.getProof([wallet.toLowerCase(), value]);

However, this results in an error because the values in the tree are formatted as strings (e.g., "uint256"), while value is passed as a bigint. This mismatch leads to invalid or empty proofs, making them unusable for verification.

Solution

To ensure compatibility with the tree's structure, the value must be converted to a string before being passed to the getProof method. This aligns the input format with the expected [address, uint256] structure of the Merkle Tree leaves.

Fixed Code:

const proof = merkleTree.getProof([wallet.toLowerCase(), value.toString()]);

Importance of Fix

1. Proof Generation: Without this fix, the proofs generated are invalid or empty, as the getProof method fails to match the input with the tree's leaves.
2. Smart Contract Compatibility: The Merkle proofs are crucial for verifying data on-chain. Incorrect proofs result in failed verification, breaking the intended functionality.
3. Data Consistency: Ensuring consistent formatting between the tree's structure and the proof input guarantees reliability and correctness.

Additional Notes

• The issue stems from a mismatch in data types: bigint vs. string. By explicitly converting the value to a string, we ensure proper functionality.
• This fix impacts the generation of proofs and their subsequent usage, so it is critical for the successful deployment of the Merkle-based system.

By addressing this issue, we ensure that the generated proofs are valid and compatible with the Merkle Tree structure and on-chain verification requirements.