Feature request: Add require and error_code equivalent of anchor

[0xzrf]

Motivation

After writing some programs in pinocchio, I realised that there's a redundancy to check specific requirements, e.g. checking whether a account is a signer

I think it's best if there's a helper function like require that checks these requirements, and a error_code equivalent of anchor to allow for custom errors

[sonicfromnewyoke]

@0xzrf you can make it on your own, as it was shown in this tutorial https://learn.blueshift.gg/en/courses/pinocchio-for-dummies/pinocchio-errors

[0xzrf]

@sonicfromnewyoke I think it'd still be useful if pinocchio provided require! and custom error via a helper macro(the way anchor provides them) from the crate itself, since custom errors are defined in almost all the programs

[burhankhaja]

@febo please assign this issue to me, i wanna add require! macro to pinocchio ? And what are your thoughts about this change ?

[febo]

As pointed out by @sonicfromnewyoke, the tutorial linked shows a good method to achieve this. I also left a comment on the PR #266 to show how you print the error in a more program-size-friendly way.

The only part missing is the require! macro, but this can be quickly added to any program:

[macro_export]
macro_rules! require {
    ( $constraint:expr, $error:expr ) => {
        if !$constraint {
            return Err($error.into());
        }
    };
}

So I am not sure if this macro would justify its own crate.