Anyhow

Anyhow is a Rust crate that provides ergonomic error handling for applications. It centers on a single, dynamic error type called anyhow::Error, which can represent any error type at runtime and can be created from most error values. This design reduces boilerplate when errors are propagated through layered code, while still preserving rich error information.

Key features include a convenient macro and methods for adding context. The anyhow! macro creates an error from a message, and with_context or context methods attach additional information as errors bubble up. The resulting error chain can be formatted to display both the high-level message and the underlying cause. The crate also offers a commonly used Result<T> alias for Result<T, anyhow::Error>, making it straightforward to return errors through functions without defining a custom error type.

Backtraces are supported when compiled with the backtrace feature, capturing the call-site location to aid debugging. Anyhow implements the standard error traits, enabling compatibility with the Rust ecosystem and with many libraries that rely on std::error::Error.

Use cases and guidance: anyhow is well-suited for binary applications, prototypes, and other code paths where a single, flexible error type is sufficient. It is typically not the best choice for library crates that publish APIs requiring stable, explicit error types, since the dynamic nature of anyhow::Error can obscure error structure from API consumers. Developers often use anyhow to simplify error handling in main or test code and then convert to or interact with more specific error types when necessary.

In summary, anyhow emphasizes ergonomic error propagation and rich context for applications, trading some static error-type exhaustiveness for ease of use and rapid development.