m06-error-handling

Rust error propagation requires distinct strategies for library versus application boundaries. Libraries should define typed errors with thiserror, while applications use anyhow for context-rich messages, ensuring errors are propagated without losing information.

Choose thiserror versus anyhow based on your project boundary. Use thiserror in libraries to define specific typed errors, and use anyhow in applications for flexible context-rich error handling and simplified error chaining.

The best way to add context to Rust Result error types is using anyhow during application-level error propagation. This preserves the original error while attaching context-rich messages, preventing information loss across function boundaries.

Designing Rust panic strategies involves choosing unwrap for unrecoverable contract violations and Result for expected recoverable failures. The structured decision framework evaluates whether a failure is truly unexpected before triggering a panic.

Testing Rust error handling patterns involves asserting that typed errors convert correctly across boundaries. Validate that Result returns propagate expected variants and that context enhancement via anyhow preserves the original error chain.

Rust libraries lose error context when returning generic Result types if they discard the original error source. Define typed errors using thiserror and implement the source trait to maintain the full error chaining context.