# facet-error
[](https://coveralls.io/github/facet-rs/facet?branch=main)
[](https://crates.io/crates/facet-error)
[](https://docs.rs/facet-error)
[](./LICENSE)
[](https://discord.gg/JhD7CwCJ8F)
# facet-error
A `thiserror` replacement powered by facet reflection. This crate is a plugin for `#[derive(Facet)]` that generates `Display` and `Error` trait implementations from doc comments.
## Usage
```rust
use facet::Facet;
#[derive(Facet, Debug)]
#[facet(derive(Error))]
#[repr(u8)]
pub enum MyError {
/// something went wrong
Unknown,
/// invalid value: {0}
InvalidValue(String),
/// invalid header (expected {expected}, found {found})
InvalidHeader { expected: String, found: String },
}
```
This generates:
- `impl Display for MyError` using doc comments as format strings
- `impl Error for MyError` with proper `source()` implementation
- Field interpolation works automatically for struct variants (e.g., `{expected}`, `{found}`)
- Tuple variants support positional interpolation (e.g., `{0}`)
## Features
- **Doc-driven Display**: Doc comments become your error messages
- **Field interpolation**: Reference struct fields by name in messages
- **Zero boilerplate**: No manual Display or Error implementations
- **Integration with facet**: Works seamlessly with the facet reflection system
## Future Work
- `#[facet(error::source)]` - mark fields as error sources
- `#[facet(error::from)]` - generate `From` implementations
- Support for error wrapping and transparent delegation
## Sponsors
Thanks to all individual sponsors:
<p> <a href="https://github.com/sponsors/fasterthanlime">
<picture>
<source media="(prefers-color-scheme: dark)" srcset="https://github.com/facet-rs/facet/raw/main/static/sponsors-v3/github-dark.svg">
<img src="https://github.com/facet-rs/facet/raw/main/static/sponsors-v3/github-light.svg" height="40" alt="GitHub Sponsors">
</picture>
</a> <a href="https://patreon.com/fasterthanlime">
<picture>
<source media="(prefers-color-scheme: dark)" srcset="https://github.com/facet-rs/facet/raw/main/static/sponsors-v3/patreon-dark.svg">
<img src="https://github.com/facet-rs/facet/raw/main/static/sponsors-v3/patreon-light.svg" height="40" alt="Patreon">
</picture>
</a> </p>
...along with corporate sponsors:
<p> <a href="https://aws.amazon.com">
<picture>
<source media="(prefers-color-scheme: dark)" srcset="https://github.com/facet-rs/facet/raw/main/static/sponsors-v3/aws-dark.svg">
<img src="https://github.com/facet-rs/facet/raw/main/static/sponsors-v3/aws-light.svg" height="40" alt="AWS">
</picture>
</a> <a href="https://zed.dev">
<picture>
<source media="(prefers-color-scheme: dark)" srcset="https://github.com/facet-rs/facet/raw/main/static/sponsors-v3/zed-dark.svg">
<img src="https://github.com/facet-rs/facet/raw/main/static/sponsors-v3/zed-light.svg" height="40" alt="Zed">
</picture>
</a> <a href="https://depot.dev?utm_source=facet">
<picture>
<source media="(prefers-color-scheme: dark)" srcset="https://github.com/facet-rs/facet/raw/main/static/sponsors-v3/depot-dark.svg">
<img src="https://github.com/facet-rs/facet/raw/main/static/sponsors-v3/depot-light.svg" height="40" alt="Depot">
</picture>
</a> </p>
...without whom this work could not exist.
## Special thanks
The facet logo was drawn by [Misiasart](https://misiasart.com/).
## License
Licensed under either of:
- Apache License, Version 2.0 ([LICENSE-APACHE](https://github.com/facet-rs/facet/blob/main/LICENSE-APACHE) or <http://www.apache.org/licenses/LICENSE-2.0>)
- MIT license ([LICENSE-MIT](https://github.com/facet-rs/facet/blob/main/LICENSE-MIT) or <http://opensource.org/licenses/MIT>)
at your option.