How to print the error from a cross chain contract call

Smart Contracts
1

I am calling the transfer method using cis2Client where i am transferring the funds from the sender to the current contract. But seems like it is failing and i dont know why. How can i print the Cis2ClientError which is being returned.

2

To log a message from a smart contract, you need to use the concordium-smart-contract-testing library and set up an integration test.
Maybe you already have this, otherwise several of our examples showcase this.

With this set up, you can use concordium_dbg! in your smart contract to print strings (example here).
These strings will only show up as part of testing, and if you use print_emitted_events (example here) and run the tests (cargo concordium test) with the --allow-debug flag.

3

But i want to understand why doesnt Cis2ClientError implement Reject so that the error can just be returned from the entrypoint method?

4

I don’t have a good answer to why it is not implemented, it probably could be.
But you can implement a type wrapping the error and implement Reject for that.
An example of this can be found here

5

I wrote smtg like this and i guess this is what is needed tbh.


impl From<Cis2ClientError<()>> for Error {
    fn from(value: Cis2ClientError<()>) -> Self {
        match value {
            Cis2ClientError::InvokeContractError(e) => match e {
                CallContractError::AmountTooLarge => Self::AmountTooLarge,
                CallContractError::MissingAccount => Self::MissingAccount,
                CallContractError::MissingContract => Self::MissingContract,
                CallContractError::MissingEntrypoint => Self::MissingEntrypoint,
                CallContractError::MessageFailed => Self::MessageFailed,
                CallContractError::LogicReject { reason, return_value } => Self::LogicReject {
                    reason,
                    return_value
                },
                CallContractError::Trap => Self::Trap,
            },
            Cis2ClientError::ParseResult => Self::ParseResult,
            Cis2ClientError::InvalidResponse => Self::InvalidResponse,
        }
    }
}
6

With above, i can just return the error and read it on the client.

1 Like
7

A discussion about this can be found here