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io::Write::write_fmt: panic if the formatter fails when the stream does not fail

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This commit is contained in:
Ralf Jung 2024-05-11 14:23:37 +02:00
parent ef15976387
commit e00f27b7be
3 changed files with 26 additions and 13 deletions
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29
tests/ui/write-fmt-errors.rs
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@ -1,9 +1,11 @@
//@ run-pass
//@ needs-unwind
#![feature(io_error_uncategorized)]
use std::fmt;
use std::io::{self, Error, Write, sink};
use std::panic::catch_unwind;
struct ErrorDisplay;
@ -15,7 +17,6 @@ impl fmt::Display for ErrorDisplay {
struct ErrorWriter;
const FORMAT_ERROR: io::ErrorKind = io::ErrorKind::Uncategorized;
const WRITER_ERROR: io::ErrorKind = io::ErrorKind::NotConnected;
impl Write for ErrorWriter {
@ -27,22 +28,28 @@ impl Write for ErrorWriter {
}
fn main() {
// Test that the error from the formatter is propagated.
let res = write!(sink(), "{} {} {}", 1, ErrorDisplay, "bar");
assert!(res.is_err(), "formatter error did not propagate");
assert_eq!(res.unwrap_err().kind(), FORMAT_ERROR);
// Test that an underlying error is propagated
let res = write!(ErrorWriter, "abc");
assert!(res.is_err(), "writer error did not propagate");
// Writer error
// Test that the error from the formatter is detected.
let res = catch_unwind(|| write!(sink(), "{} {} {}", 1, ErrorDisplay, "bar"));
let err = res.expect_err("formatter error did not lead to panic").downcast::<&str>().unwrap();
assert!(
err.contains("formatting trait implementation returned an error"),
"unexpected panic: {}", err
);
// Writer error when there's some string before the first `{}`
let res = write!(ErrorWriter, "abc {}", ErrorDisplay);
assert!(res.is_err(), "writer error did not propagate");
assert_eq!(res.unwrap_err().kind(), WRITER_ERROR);
// Formatter error
let res = write!(ErrorWriter, "{} abc", ErrorDisplay);
assert!(res.is_err(), "formatter error did not propagate");
assert_eq!(res.unwrap_err().kind(), FORMAT_ERROR);
// Formatter error when the `{}` comes first
let res = catch_unwind(|| write!(ErrorWriter, "{} abc", ErrorDisplay));
let err = res.expect_err("formatter error did not lead to panic").downcast::<&str>().unwrap();
assert!(
err.contains("formatting trait implementation returned an error"),
"unexpected panic: {}", err
);
}