From<docs>
This library provides a convenient derive macro for the standard library's
[core::fmt::Display] trait.
toml
[dependencies]
displaydoc = "0.2"
Compiler support: requires rustc 1.56+
Demonstration alongside the [Error][std::error::Error] derive macro from thiserror,
to propagate source locations from [io::Error][std::io::Error] with the #[source] attribute:
```rust
use std::io;
use displaydoc::Display;
use thiserror::Error;
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,
}
let error = DataStoreError::Redaction("CLASSIFIED CONTENT".to_string());
assert!("the data for key CLASSIFIED CONTENT is not available" == &format!("{}", error));
``
*Note that although [io::Error][std::io::Error] implementsDisplay, we do not add it to the
generated message forDataStoreError::Disconnect, since it is already made available via
#[source]`. See further context on avoiding duplication in error reports at the rust blog
here.*
fmt::Display impl is generated for your enum if you provide
a docstring comment on each variant as shown above in the example. The
Display derive macro supports a shorthand for interpolating fields from
the error:
/// {var} ⟶ write!("{}", self.var)/// {0} ⟶ write!("{}", self.0)/// {var:?} ⟶ write!("{:?}", self.var)/// {0:?} ⟶ write!("{:?}", self.0)pub struct Error
let error: Error<&str> = Error("muahaha i am an error"); assert!("oh no, an error: muahaha i am an error" == &format!("{}", error)); ```
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.
Is this crate no_std compatible?
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.Does this crate work with Path and PathBuf via the Display trait?
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!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.