1 use crate::lib::{Debug, Display};
2 
3 /// Either a re-export of std::error::Error or a new identical trait, depending
4 /// on whether Serde's "std" feature is enabled.
5 ///
6 /// Serde's error traits [`serde::ser::Error`] and [`serde::de::Error`] require
7 /// [`std::error::Error`] as a supertrait, but only when Serde is built with
8 /// "std" enabled. Data formats that don't care about no\_std support should
9 /// generally provide their error types with a `std::error::Error` impl
10 /// directly:
11 ///
12 /// ```edition2021
13 /// #[derive(Debug)]
14 /// struct MySerError {...}
15 ///
16 /// impl serde::ser::Error for MySerError {...}
17 ///
18 /// impl std::fmt::Display for MySerError {...}
19 ///
20 /// // We don't support no_std!
21 /// impl std::error::Error for MySerError {}
22 /// ```
23 ///
24 /// Data formats that *do* support no\_std may either have a "std" feature of
25 /// their own:
26 ///
27 /// ```toml
28 /// [features]
29 /// std = ["serde/std"]
30 /// ```
31 ///
32 /// ```edition2021
33 /// #[cfg(feature = "std")]
34 /// impl std::error::Error for MySerError {}
35 /// ```
36 ///
37 /// ... or else provide the std Error impl unconditionally via Serde's
38 /// re-export:
39 ///
40 /// ```edition2021
41 /// impl serde::ser::StdError for MySerError {}
42 /// ```
43 pub trait Error: Debug + Display {
44     /// The underlying cause of this error, if any.
source(&self) -> Option<&(Error + 'static)>45     fn source(&self) -> Option<&(Error + 'static)> {
46         None
47     }
48 }
49