refactor-state-errors

Refactoring Rust service errors into domain-specific enums involves replacing plain end-user error structs in state.rs with a domain error enum using thiserror, keeping message text centralized within the enum variants themselves.

Using thiserror for domain error handling in Rust allows you to define domain-specific error enums that represent service errors without HTTP or wire knowledge, enforcing a clean separation between domain logic and handler error shaping.

The best way to separate domain errors from wire format responses is to move domain-to-wire error mapping into handlers.rs, exhaustively matching enum variants to wire responses while using err.to_string() to maintain a single source of truth for messages.

Yes, you need to add thiserror to your Cargo.toml dependencies to use thiserror for error refactoring, replacing state.rs error struct constructions with explicit enum variants and updating handlers.rs accordingly.

Exhaustive matching when mapping Rust error enums to wire responses requires the handler error-shaping function to explicitly cover every domain enum variant, ensuring all possible service errors are translated into appropriate wire formats without missing cases.

You should move error shaping out of state.rs in a Rust service crate when your service logic needs to represent errors without HTTP or wire knowledge, centralizing message text in domain enums and handling wire formatting exclusively in the handler layer.