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Add top-level documentation on reporting errors #466

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Nov 4, 2024
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Add top-level documentation on reporting errors #466

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58 changes: 58 additions & 0 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
//! - [`Options`](OptionExt)
#![cfg_attr(feature = "futures", doc = " - [`Futures`](futures::TryFutureExt)")]
#![cfg_attr(feature = "futures", doc = " - [`Streams`](futures::TryStreamExt)")]
//! - [Error reporting](#reporting)
//! - Suitable for libraries and applications
//! - `no_std` compatibility
//! - Generic types and lifetimes
Expand Down Expand Up @@ -200,6 +201,63 @@
//! your error type to be used in multithreaded programs, by changing
//! `dyn std::error::Error` to `dyn std::error::Error + Send + Sync`.
//!
//! ## Reporting
//!
//! Printing an error via [`Display`][]
//! will only show the top-level error message without the underlying sources.
//! For an extended error report,
//! SNAFU offers a user-friendly error output mechanism.
//! It prints the main error and all underlying errors in the chain,
//! from the most recent to the oldest,
//! plus the [backtrace](Backtrace) if applicable.
//! This is done by using the [`macro@report`] procedural macro
//! or the [`Report`] type directly.
//!
//! ```no_run
//! use snafu::prelude::*;
//!
//! #[derive(Debug, Snafu)]
//! #[snafu(display("Could not load configuration file {path}"))]
//! struct ConfigFileError {
//! source: std::io::Error,
//! path: String,
//! }
//!
//! fn read_config_file(path: &str) -> Result<String, ConfigFileError> {
//! std::fs::read_to_string(path).context(ConfigFileSnafu { path })
//! }
//!
//! #[snafu::report]
//! fn main() -> Result<(), ConfigFileError> {
//! read_config_file("bad-config.ini")?;
//! Ok(())
//! }
//! ```
//!
//! This will print:
//!
//! ```none
//! Error: Could not load configuration file bad-config.ini
//!
//! Caused by this error:
//! 1: No such file or directory (os error 2)
//! ```
//!
//! Which shows the underlying errors, unlike [`Display`]:
//!
//! ```none
//! Error: Could not load configuration file bad-config.ini
//! ```
//!
//! ... and is also more readable than the [`Debug`] output:
//!
//! ```none
//! Error: ConfigFileError { source: Os { code: 2, kind: NotFound, message: "No such file or directory" }, path: "bad-config.ini" }
//! ```
//!
//! [`Display`]: core::fmt::Display
//! [`Debug`]: core::fmt::Debug
//!
//! ## Next steps
//!
//! Read the documentation for the [`Snafu`][] macro to see all of the
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