diff options
Diffstat (limited to 'vendor/thiserror/README.md')
| -rw-r--r-- | vendor/thiserror/README.md | 222 |
1 files changed, 0 insertions, 222 deletions
diff --git a/vendor/thiserror/README.md b/vendor/thiserror/README.md deleted file mode 100644 index 9de063c..0000000 --- a/vendor/thiserror/README.md +++ /dev/null @@ -1,222 +0,0 @@ -derive(Error) -============= - -[<img alt="github" src="https://img.shields.io/badge/github-dtolnay/thiserror-8da0cb?style=for-the-badge&labelColor=555555&logo=github" height="20">](https://github.com/dtolnay/thiserror) -[<img alt="crates.io" src="https://img.shields.io/crates/v/thiserror.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/thiserror) -[<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-thiserror-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs" height="20">](https://docs.rs/thiserror) -[<img alt="build status" src="https://img.shields.io/github/actions/workflow/status/dtolnay/thiserror/ci.yml?branch=master&style=for-the-badge" height="20">](https://github.com/dtolnay/thiserror/actions?query=branch%3Amaster) - -This library provides a convenient derive macro for the standard library's -[`std::error::Error`] trait. - -[`std::error::Error`]: https://doc.rust-lang.org/std/error/trait.Error.html - -```toml -[dependencies] -thiserror = "1.0" -``` - -*Compiler support: requires rustc 1.56+* - -<br> - -## Example - -```rust -use thiserror::Error; - -#[derive(Error, Debug)] -pub enum DataStoreError { - #[error("data store disconnected")] - Disconnect(#[from] io::Error), - #[error("the data for key `{0}` is not available")] - Redaction(String), - #[error("invalid header (expected {expected:?}, found {found:?})")] - InvalidHeader { - expected: String, - found: String, - }, - #[error("unknown data store error")] - Unknown, -} -``` - -<br> - -## Details - -- Thiserror deliberately does not appear in your public API. You get the same - thing as if you had written an implementation of `std::error::Error` by hand, - and switching from handwritten impls to thiserror or vice versa is not a - breaking change. - -- Errors may be enums, structs with named fields, tuple structs, or unit - structs. - -- A `Display` impl is generated for your error if you provide `#[error("...")]` - messages on the struct or each variant of your enum, as shown above in the - example. - - The messages support a shorthand for interpolating fields from the error. - - - `#[error("{var}")]` ⟶ `write!("{}", self.var)` - - `#[error("{0}")]` ⟶ `write!("{}", self.0)` - - `#[error("{var:?}")]` ⟶ `write!("{:?}", self.var)` - - `#[error("{0:?}")]` ⟶ `write!("{:?}", self.0)` - - These shorthands can be used together with any additional format args, which - may be arbitrary expressions. For example: - - ```rust - #[derive(Error, Debug)] - pub enum Error { - #[error("invalid rdo_lookahead_frames {0} (expected < {})", i32::MAX)] - InvalidLookahead(u32), - } - ``` - - If one of the additional expression arguments needs to refer to a field of the - struct or enum, then refer to named fields as `.var` and tuple fields as `.0`. - - ```rust - #[derive(Error, Debug)] - pub enum Error { - #[error("first letter must be lowercase but was {:?}", first_char(.0))] - WrongCase(String), - #[error("invalid index {idx}, expected at least {} and at most {}", .limits.lo, .limits.hi)] - OutOfBounds { idx: usize, limits: Limits }, - } - ``` - -- A `From` impl is generated for each variant containing a `#[from]` attribute. - - Note that the variant must not contain any other fields beyond the source - error and possibly a backtrace. A backtrace is captured from within the `From` - impl if there is a field for it. - - ```rust - #[derive(Error, Debug)] - pub enum MyError { - Io { - #[from] - source: io::Error, - backtrace: Backtrace, - }, - } - ``` - -- The Error trait's `source()` method is implemented to return whichever field - has a `#[source]` attribute or is named `source`, if any. This is for - identifying the underlying lower level error that caused your error. - - The `#[from]` attribute always implies that the same field is `#[source]`, so - you don't ever need to specify both attributes. - - Any error type that implements `std::error::Error` or dereferences to `dyn - std::error::Error` will work as a source. - - ```rust - #[derive(Error, Debug)] - pub struct MyError { - msg: String, - #[source] // optional if field name is `source` - source: anyhow::Error, - } - ``` - -- The Error trait's `provide()` method is implemented to provide whichever field - has a type named `Backtrace`, if any, as a `std::backtrace::Backtrace`. - - ```rust - use std::backtrace::Backtrace; - - #[derive(Error, Debug)] - pub struct MyError { - msg: String, - backtrace: Backtrace, // automatically detected - } - ``` - -- If a field is both a source (named `source`, or has `#[source]` or `#[from]` - attribute) *and* is marked `#[backtrace]`, then the Error trait's `provide()` - method is forwarded to the source's `provide` so that both layers of the error - share the same backtrace. - - ```rust - #[derive(Error, Debug)] - pub enum MyError { - Io { - #[backtrace] - source: io::Error, - }, - } - ``` - -- Errors may use `error(transparent)` to forward the source and Display methods - straight through to an underlying error without adding an additional message. - This would be appropriate for enums that need an "anything else" variant. - - ```rust - #[derive(Error, Debug)] - pub enum MyError { - ... - - #[error(transparent)] - Other(#[from] anyhow::Error), // source and Display delegate to anyhow::Error - } - ``` - - Another use case is hiding implementation details of an error representation - behind an opaque error type, so that the representation is able to evolve - without breaking the crate's public API. - - ```rust - // PublicError is public, but opaque and easy to keep compatible. - #[derive(Error, Debug)] - #[error(transparent)] - pub struct PublicError(#[from] ErrorRepr); - - impl PublicError { - // Accessors for anything we do want to expose publicly. - } - - // Private and free to change across minor version of the crate. - #[derive(Error, Debug)] - enum ErrorRepr { - ... - } - ``` - -- See also the [`anyhow`] library for a convenient single error type to use in - application code. - - [`anyhow`]: https://github.com/dtolnay/anyhow - -<br> - -## Comparison to anyhow - -Use thiserror if you care about designing your own dedicated error type(s) so -that the caller receives exactly the information that you choose in the event of -failure. This most often applies to library-like code. Use [Anyhow] if you don't -care what error type your functions return, you just want it to be easy. This is -common in application-like code. - -[Anyhow]: https://github.com/dtolnay/anyhow - -<br> - -#### License - -<sup> -Licensed under either of <a href="LICENSE-APACHE">Apache License, Version -2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option. -</sup> - -<br> - -<sub> -Unless you explicitly state otherwise, any contribution intentionally submitted -for inclusion in this crate by you, as defined in the Apache-2.0 license, shall -be dual licensed as above, without any additional terms or conditions. -</sub> |