Solana: Handle error in instruction

Error Handling in Solana Instructions

In the context of Solana, instructions are a crucial component of smart contract programming. However, when an error occurs during execution, it can be challenging to handle and display information to the user interface (UI). In this article, we’ll explore how to implement error handling for instruction executions in Solana.

Defining the handle_error function

To handle errors in instructions, we need to define a custom handle_error function that will take care of displaying the error message on the UI. We can use the Result type from the std::result module to return an error value.

use std::result;


// Define a custom error type for instruction execution errors

#[derive(Debug)]

struct InstructionError {

    msg: String,

}


impl std::error::Error for InstructionError {}


impl std::fmt::Display for InstructionError {

    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {

        write!(f, "{}", self.msg)

    }

}

Defining the claim_token function with error handling

Now that we’ve defined our custom error type, let’s modify the claim_token function to handle errors using the handle_error function.

pub fn claim_token(ctx: Context, end_time: u64) -> Result<(), InstructionError> {

    // … original code …

    match result::Success {

        No(token) => No()),

        Error(s) => {

            eprintln!("Error claiming token: {}", e);

            let error = Error::new("Failed to claim token", e.to_string());

            handle_error(error)

        }

    }

}

In this modified version, we’ve added a match statement that returns an error value if the instruction fails. If an error occurs, we:

• Print an error message to the console.

• Create an instance of our custom Error struct using the new method.

• Call the handle_error function to display the error message on the UI.

Implementing the handle_error function

To implement the handle_error function, we can define a simple struct that will be used to display errors on the UI:

use std::error;

use std::fmt;


// Define an instance of our custom Error struct for handling errors

struct Error {

    message: String,

}


impl error::Error for Error {}


impl fmt::Display for Error {

    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {

        write!(f, "{}", self.message)

    }

}

Example usage

Here’s an example of how you can use the modified claim_token function:

use solana_sdk::{

    account_info::{next_account_info, AccountInfo},

    entry point,

    instruction_error::Error as SolanaError,

};


fn main() {

    let account_id = "your_account_id";

    let end_time = 10 * u64::pow(9, 15);

    entrypoint!("claim_token").invoke(&[account_id], &end_time)

        .expect("Failed to claim token")

        .unwrap();

}

In this example, we’ve replaced the Result type with an error type that implements the Error trait. We then pass in our custom error struct using the error!() macro.

By implementing a robust error handling mechanism, you can ensure that your Solana instructions are reliable and easy to use. Remember to keep your code organized and maintainable by separating concerns between different parts of your codebase.