How to use thiserror crate in Rust error types

Use the thiserror crate to define an error enum with the #[derive(thiserror::Error)] attribute and annotate variants with #[error(...)] for messages or #[from] for automatic conversion.

use thiserror::Error;

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

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

Add thiserror = "1.0.60" to your Cargo.toml dependencies.

The thiserror crate lets you create custom error types that automatically handle formatting and converting other errors into your own. Think of it as a template system for error messages that saves you from writing repetitive boilerplate code. You use it whenever you need to return specific, descriptive errors from your functions instead of generic ones.