6cfafad3c5
Previously, if an error was returned from the formatter that did not originate in an underlying writer error, Write::write_fmt would return successfully even if the formatting did not complete (was interrupted by an `fmt::Error` return). Now we choose to emit an io::Error with kind Other for formatter errors. Since this may reveal error returns from `write!()` and similar that previously passed silently, it's a kind of a [breaking-change].
55 lines
1.8 KiB
Rust
55 lines
1.8 KiB
Rust
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use std::fmt;
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use std::io::{self, Error, Write, sink};
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struct ErrorDisplay;
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impl fmt::Display for ErrorDisplay {
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fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result {
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Err(fmt::Error)
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}
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}
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struct ErrorWriter;
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const FORMAT_ERROR: io::ErrorKind = io::ErrorKind::Other;
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const WRITER_ERROR: io::ErrorKind = io::ErrorKind::NotConnected;
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impl Write for ErrorWriter {
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fn write(&mut self, _buf: &[u8]) -> io::Result<usize> {
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Err(Error::new(WRITER_ERROR, "not connected"))
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}
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fn flush(&mut self) -> io::Result<()> { Ok(()) }
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}
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fn main() {
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// Test that the error from the formatter is propagated.
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let res = write!(sink(), "{} {} {}", 1, ErrorDisplay, "bar");
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assert!(res.is_err(), "formatter error did not propagate");
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assert_eq!(res.unwrap_err().kind(), FORMAT_ERROR);
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// Test that an underlying error is propagated
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let res = write!(ErrorWriter, "abc");
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assert!(res.is_err(), "writer error did not propagate");
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// Writer error
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let res = write!(ErrorWriter, "abc {}", ErrorDisplay);
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assert!(res.is_err(), "writer error did not propagate");
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assert_eq!(res.unwrap_err().kind(), WRITER_ERROR);
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// Formatter error
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let res = write!(ErrorWriter, "{} abc", ErrorDisplay);
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assert!(res.is_err(), "formatter error did not propagate");
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assert_eq!(res.unwrap_err().kind(), FORMAT_ERROR);
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}
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