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About the developer

yaahc
280 Stars 12 Forks Other 78 Commits 3 Opened issues

Description

A derive macro for implementing the display Trait via a doc comment and string interpolation

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derive(Display) ///
From

Latest Version Rust Documentation

This library provides a convenient derive macro for the standard library's

core::fmt::Display
trait.

[dependencies]
displaydoc = "0.2"

Compiler support: requires rustc 1.45+


Example

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, }


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.


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 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!

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.


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.

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