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|
//! This library provides a convenient derive macro for the standard library's
//! [`core::fmt::Display`] trait.
//!
//! [`core::fmt::Display`]: https://doc.rust-lang.org/std/fmt/trait.Display.html
//!
//! ```toml
//! [dependencies]
//! displaydoc = "0.2"
//! ```
//!
//! *Compiler support: requires rustc 1.31+*
//!
//! <br>
//!
//! ## Example
//!
//! ```rust
//! use std::io;
//! use displaydoc::Display;
//! use thiserror::Error;
//!
//! #[derive(Display, Error, Debug)]
//! pub enum DataStoreError {
//! /// data store disconnected
//! Disconnect(#[source] io::Error),
//! /// the data for key `{0}` is not available
//! Redaction(String),
//! /// invalid header (expected {expected:?}, found {found:?})
//! InvalidHeader {
//! expected: String,
//! found: String,
//! },
//! /// unknown data store error
//! Unknown,
//! }
//! ```
//!
//! <br>
//!
//! ## Details
//!
//! - A `Display` impl is generated for your type if you provide doc comment
//! 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.
//!
//! - `/// {var}` ⟶ `write!("{}", self.var)`
//! - `/// {0}` ⟶ `write!("{}", self.0)`
//! - `/// {var:?}` ⟶ `write!("{:?}", self.var)`
//! - `/// {0:?}` ⟶ `write!("{:?}", self.0)`
//!
//! - Two optional attributes can be added to your types next to the derive:
//!
//! - `#[ignore_extra_doc_attributes]` makes the macro ignore any doc
//! comment attributes (or `///` lines) after the first. Multi-line
//! comments using `///` are otherwise treated as an error, so use this
//! attribute or consider switching to block doc comments (`/** */`).
//!
//! - `#[prefix_enum_doc_attributes]` combines the doc comment message on
//! your enum itself with the messages for each variant, in the format
//! “enum: variant”. When added to an enum, the doc comment on the enum
//! becomes mandatory. When added to any other type, it has no effect.
//!
//! - In case you want to have an independent doc comment, the
//! `#[displaydoc("...")` atrribute may be used on the variant or struct to
//! override it.
//!
//! <br>
//!
//! ## FAQ
//!
//! 1. **Is this crate `no_std` compatible?**
//! * Yes! This crate implements the `core::fmt::Display` trait not the `std::fmt::Display` trait so it should work in `std` and `no_std` environments. Just add `default-features = false`.
//!
//! 2. **Does this crate work with `Path` and `PathBuf` via the `Display` trait?**
//! * Yuuup. This crate uses @dtolnay's [autoref specialization technique](https://github.com/dtolnay/case-studies/blob/master/autoref-specialization/README.md) to add a special trait for types to get the display impl, it then specializes for `Path` and `PathBuf` and when either of these types are found it calls `self.display()` to get a `std::path::Display<'_>` type which can be used with the Display format specifier!
#![doc(html_root_url = "https://docs.rs/displaydoc/0.2.3")]
#![cfg_attr(docsrs, feature(doc_cfg))]
#![warn(
rust_2018_idioms,
unreachable_pub,
bad_style,
const_err,
dead_code,
improper_ctypes,
non_shorthand_field_patterns,
no_mangle_generic_items,
overflowing_literals,
path_statements,
patterns_in_fns_without_body,
private_in_public,
unconditional_recursion,
unused,
unused_allocation,
unused_comparisons,
unused_parens,
while_true
)]
#![allow(clippy::try_err)]
#[allow(unused_extern_crates)]
extern crate proc_macro;
mod attr;
mod expand;
mod fmt;
use proc_macro::TokenStream;
use syn::{parse_macro_input, DeriveInput};
/// Derive macro for implementing `Display` via doc comment attributes
#[proc_macro_derive(
Display,
attributes(ignore_extra_doc_attributes, prefix_enum_doc_attributes, displaydoc)
)]
pub fn derive_error(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as DeriveInput);
expand::derive(&input)
.unwrap_or_else(|err| err.to_compile_error())
.into()
}
|
