Custom Program Errors - Need Better Documentation?

Question

I have been working with compressing NFTs and I experience custom program errors in transactions like this one

custom program error: 0xbc4

This might not be the most up to date it could be, it has some error handling though:

https://github.com/solana-labs/solana-program-library/blob/master/token/program/src/error.rs

Answer 1

If that's from an Anchor program, the error is this:

#[msg("The program expected this account to be already initialized")]
AccountNotInitialized,

https://github.com/coral-xyz/anchor/blob/master/lang/src/error.rs#L185