| commit | 72ad2bb16df9e105deabf1cb718b655381b8749f | [log] [tgz] |
|---|---|---|
| author | Android Build Coastguard Worker <[email protected]> | Sat Aug 03 03:11:31 2024 +0000 |
| committer | Android Build Coastguard Worker <[email protected]> | Sat Aug 03 03:11:31 2024 +0000 |
| tree | 970fae9ffd0454eb352c1385a31367d34d37fc7b | |
| parent | 22d28dfd229eaaaa1d10a7c40f6ab9bfdf6b853c [diff] | |
| parent | a52c7af70151f7924ee14b3936f2688b8082eaa4 [diff] |
Snap for 12177962 from a52c7af70151f7924ee14b3936f2688b8082eaa4 to 24Q4-release Change-Id: I4cc03b6f8fbf109d04112dfa0e7e407e264f2f28
From<docs>
This library provides a convenient derive macro for the standard library's core::fmt::Display trait.
[dependencies] displaydoc = "0.2"
Compiler support: requires rustc 1.56+
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:
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, } 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] implements Display, we do not add it to the generated message for DataStoreError::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)/// oh no, an error: {0} #[derive(Display)] pub struct Error<E>(pub E); 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!