How to use thiserror crate in Rust error derive

Use the thiserror::Error derive macro on your error enum to automatically implement std::error::Error and define display messages via attributes.

use thiserror::Error;

#[derive(Error, Debug)]
pub enum Error {
    #[error("No config for '{0}'")]
    NoConfig(String),

    #[error(transparent)]
    Mdbook(#[from] mdbook_preprocessor::errors::Error),
}

This pattern allows you to define custom error messages with placeholders and transparently wrap other errors using #[from] for automatic conversion.

The thiserror crate automatically generates the boilerplate code needed to make your custom errors work with Rust's standard error handling system. Instead of writing repetitive code to display error messages or convert between different error types, you just add a small tag to your error list. It's like having a template that fills in the boring parts so you can focus on what the error actually means.