Help me with this error

[Aashim-Limbu]

Discussion: Identifying the Cause of Unexpected Revert in Next.js Integration with Etherscan

Context:

I am integrating my project with Next.js and encountered an unexpected revert while interacting with Etherscan. The issue arises during a read operation in my Solidity smart contract. Given that this is a read operation, I assume it is not related to gas limits.

Here’s the relevant part of my Solidity code:

struct File {
    string fileHash;
    uint256 fee;
}
mapping(address => File[]) private s_addressToFiles;

function getMyFile(uint256 fileCounter) 
    external 
    view 
    returns (string memory fHash, uint256 fee) 
{
    File memory file = s_addressToFiles[msg.sender][fileCounter];
    return (file.fileHash, file.fee);
}

function getFileFee(address _owner, uint256 _fileId) 
    external 
    view 
    returns (uint256) 
{
    if (_fileId >= s_addressToFiles[_owner].length) {
        revert EHRManagement__FileNotFound();
    }
    return s_addressToFiles[_owner][_fileId].fee;
}

Issue:

-

• When executing getFileFee() or getMyFile() for specific file indices or owners, the call sometimes reverts on Etherscan with an error message indicating a problem.
• As this is a read-only function, I am confused about the potential reasons for the revert.

Observations:

• The revert condition (_fileId >= s_addressToFiles[_owner].length) is explicitly defined, but I’ve double-checked the file IDs and owner addresses in my test cases.
• The data mappings seem correct in storage, and the issue is not consistently reproducible.

Questions:

1. What might be causing the revert in this case, especially during a read operation?
2. Could it be related to data corruption in the storage mappings, or is there another explanation?
3. How can I debug this issue effectively, given that it happens on Etherscan and not locally i mean in test?

You can copy and paste this into any markdown-compatible platform.

[EngrPips]

Honestly, It is tough to say what could be wrong, considering the issue is not persistent. It could be an issue on etherscan, considering it didn't occur when you were testing stuff locally.

[KMean]

@Aashim-Limbu did you try to check for out of bounds in your getMyFile?

function getMyFile(uint256 fileCounter) 
    external 
    view 
    returns (string memory fHash, uint256 fee) 
{
    // Boundary check
    if (fileCounter >= s_addressToFiles[msg.sender].length) {
        revert("File index out of bounds");
    }
    File memory file = s_addressToFiles[msg.sender][fileCounter];
    return (file.fileHash, file.fee);
}

You can use forge to test it forking a chain.

[Aashim-Limbu]

@KMean:

I would say no, I didn’t include an out-of-bounds check in my getMyFile function. However, I am confident that the first file associated with the user’s address contains a valid file instance because I can successfully query for the file fee.

Here is an image showing the file fee query:

Problem

While I can query the file fee, I am unable to retrieve the destructured values of the File struct (i.e., fileHash and fee) as shown in the image above.

Questions

1. Could the issue be related to the absence of an explicit out-of-bounds check in the getMyFile function?
2. What could prevent the destructuring of the File struct values in this case, even though the file fee query works as expected?
3. Are there additional debugging steps I should follow to trace this issue effectively?

[KMean]

@KMean:

I would say no, I didn’t include an out-of-bounds check in my getMyFile function. However, I am confident that the first file associated with the user’s address contains a valid file instance because I can successfully query for the file fee.

Here is an image showing the file fee query:

Problem

While I can query the file fee, I am unable to retrieve the destructured values of the File struct (i.e., fileHash and fee) as shown in the image above.

Questions

1. Could the issue be related to the absence of an explicit out-of-bounds check in the getMyFile function?

2. What could prevent the destructuring of the File struct values in this case, even though the file fee query works as expected?

3. Are there additional debugging steps I should follow to trace this issue effectively?

I would do it at least just to test it so you can log what the error is. It's tricky to say what calldata you're sending to the contract from the UI without seeing the UI code.

[Aashim-Limbu]

Yeah that does make sense but you know i haven't integrated to the UI i was just testing if things works well in etherscan.io but i found that it do not work for getMyFile . while rest of the part works perfectly fine for me

[EngrPips]

Hey @Aashim-Limbu, Are you sure you are calling the getMyFile function with an address that has created a file on the contract?

[EngrPips]

Please share a link to the contract address so maybe I can interact on my end too and see how things play out. You are working on ETH Sepolia, right?

[Aashim-Limbu]

@EngrPips yup 😀.
contract address : 0x49Fc8312908F6c3982571DdBAf63EeeaC35B2830

[EngrPips]

Thanks

[KMean]

0x49Fc8312908F6c3982571DdBAf63EeeaC35B2830

as mentioned by @EngrPips I guess that the problem arise because the function getMyFile fetches files for msg.sender. If you're testing this on Etherscan you should make sure that you're connected with the correct address (the one that uploaded the file). If msg.sender has no files, the array s_addressToFiles[msg.sender] will be empty, even if other addresses have uploaded files. In fact calling getAllUserFile from my side to verify if the caller (msg.sender) has files stored in s_addressToFiles returns an empty array.

what does getAllUserFile returns if you call it from the owner?

EDIT:

I tried to upload a document on your contract and calling getAllUserFile and indeed returns the correct array with file and fee in it. As I said I would add some checks in getMyFile to narrow down the problem

function getMyFile(uint256 fileCounter) external view returns (string memory fHash, uint256 fee) {
        uint256 length = s_addressToFiles[msg.sender].length;

        // Ensure the caller has uploaded files
        if (length == 0) {
            revert("Caller has no files uploaded");
        }

        // Validate fileCounter is within bounds
        if (fileCounter >= length) {
            revert("Index out of bounds");
        }

        // Safely access the file
        File memory file = s_addressToFiles[msg.sender][fileCounter];
        return (file.fileHash, file.fee);
    }

[Aashim-Limbu]

@KMean Thank you for the concern .