Anyhow Rust Error Handling Library

Anyhow is a free and open-source Rust library that provides ergonomic error handling for applications, making it easy to work with multiple error types and attach context to errors. Created by David Tolnay (also the creator of Serde, syn, quote, and proc-macro2) in 2019, Anyhow is one of the most popular Rust libraries with over 100 million downloads, widely used in CLI tools, daemons, and application-level Rust code. Key features: error chaining: anyhow::Result allows returning any error type implementing std::error::Error, automatically converting them via the ? operator without explicit mapping. This eliminates the need for custom error enums in application code. Context attachment: the .context() and .with_context() methods attach human-readable context strings to errors, creating an error chain showing the full path of what went wrong. For example, a low-level IO error can be enriched with context like 'failed to open configuration file'. Backtrace support: automatically captures a backtrace when an error is created (on nightly Rust or with the backtrace feature), making it easy to locate error origins. Display formatting: {:?} (Debug) shows the full error chain with context, while {} (Display) shows only the top-level error. Downcasting: errors stored as anyhow::Error can be downcast to original concrete types via .downcast_ref() and .downcast_mut(). Macros: anyhow! creates an error from a format string, bail! returns an error early, ensure! for conditional error returns. Compatible with thiserror (for library-level error types). no-std support with alloc. MIT/Apache-2.0.