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#![cfg(feature="std")]
use snafu::prelude::*;
use std::{
error::Error as StdError,
fs, io,
path::{Path, PathBuf},
ptr,
};
#[derive(Debug, Snafu)]
#[snafu(display("filename: {}, source: {}", filename.display(), source))]
struct Error {
filename: PathBuf,
source: io::Error,
}
type Result<T, E = Error> = std::result::Result<T, E>;
fn example(filename: impl AsRef<Path>) -> Result<()> {
let filename = filename.as_ref();
let _config = fs::read(filename).context(Snafu { filename })?;
Ok(())
}
#[test]
fn implements_error() {
fn check<T: StdError>() {}
check::<Error>();
let path = "/some/directory/that/does/not/exist";
let e = example(path).unwrap_err();
assert_eq!(e.filename, Path::new(path));
let source = e.source().expect("Source must be present");
let source_as_io_error = source
.downcast_ref::<io::Error>()
.expect("Source must be io::Error");
assert!(ptr::eq(source_as_io_error, &e.source));
let display = e.to_string();
assert!(
display.starts_with("filename: /some/directory/that/does/not/exist, source: "),
"Display string incorrect, is: {}",
display,
);
}
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