IBC Reply Error Handling

ibc_reply.rs

#[entry_point]
pub fn ibc_packet_receive(
    deps: DepsMut,
    _env: Env,
    msg: IbcPacketReceiveMsg,
) -> Result<IbcReceiveResponse, Never> {
    // other parse code here...
    
    let msg = Cw20ExecuteMsg::Transfer {
        recipient,
        amount: coin.amount,
    };
    let exec = WasmMsg::Execute {
        contract_addr: coin.address,
        msg: to_binary(&msg).unwrap(),
        funds: vec![],
    };
    let sub_msg = SubMsg::reply_on_error(exec, SEND_TOKEN_ID);
    
    // return submessage with pre-emptive success packet in the data field
    IbcReceiveResponse::new()
        .set_ack(ack_success())
        .add_submessage(sub_msg)
        .add_attributes(attributes)
}

#[entry_point]
pub fn reply(_deps: DepsMut, _env: Env, reply: Reply) -> Result<Response, ContractError> {
    if reply.id != SEND_TOKEN_ID {
        return Err(ContractError::UnknownReplyId { id: reply.id });
    }
    // always return a success... just overwrite the data field (ack packet) on error
    let res = match reply.result {
        ContractResult::Ok(_) => Response::new(),
        ContractResult::Err(err) => {
            // encode an acknowledgement error
            Response::new().set_data(ack_fail(err))
        }
    };
    Ok(res)
}