Crate uniquote

This crate allows quoting strings for use in output. It works similarly to str::escape_debug, but the result is meant to be shown to users. Simply call Quote::quote on an argument passed to println! or a similar macro to quote it.

One of the primary uses for this crate is displaying paths losslessly. Since Path has no Display implementation, it is usually output by calling Path::display or Path::to_string_lossy beforehand. However, both of those methods are lossy; they replace all invalid characters with REPLACEMENT_CHARACTER. This crate escapes those invalid characters instead, allowing them to always be displayed correctly.

Unprintable characters are also escaped, to give unambiguous output. All code points are supported, but the Unicode Standard does not define which are unprintable. So, a typical subset is used that may change between minor versions. Guarantees are made in the next section.

Format

The format used to represent strings is different from typical Debug output, because it is designed to show most paths correctly on any platform. In particular, backslashes (\) will never be escaped, since Windows uses them as directory separators. They exist in almost every path users provide on Windows.

In their place, curly braces ({ and }) are substituted, since they appear less frequently. Thus, normal paths should not require any escaping at all. The intention is to make the result easily readable on any system.

These are some examples of the quoting format:

use uniquote::Quote;

assert_eq!(r#""foo bar""#,      "foo bar".quote().to_string());
assert_eq!(r#""foo{~n}bar""#,   "foo\nbar".quote().to_string());
assert_eq!(r#""foo{~u7f}bar""#, "foo\x7Fbar".quote().to_string());
assert_eq!(r#""foo{"}bar""#,    "foo\"bar".quote().to_string());

The only ASCII characters escaped are ", {, }, and control characters. Other characters are not guaranteed to be quoted in a specific way but will generally only be escaped if unprintable.

Features

These features are optional and can be enabled or disabled in a “Cargo.toml” file.

Default Features

• alloc - Provides implementations of Quote for types that require allocation. This feature is enabled automatically when the std feature is enabled.

• std - Provides implementations of Quote for types that require the standard library. When this feature is disabled, this crate can be used in #![no_std] environments.

Examples

Printing Command Line Arguments:

use std::env;

use uniquote::Quote;

for (i, arg) in env::args_os().enumerate() {
    println!("arg #{} is {}", i, arg.quote());
}

Creating a Descriptive Error Message:

use std::error::Error;
use std::fmt;
use std::fmt::Display;
use std::fmt::Formatter;
use std::path::PathBuf;

use uniquote::Quote;

#[derive(Debug)]
struct FileNotFoundError(PathBuf);

impl Display for FileNotFoundError {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        write!(f, "file not found at {}", self.0.quote())
    }
}

impl Error for FileNotFoundError {}

Structs

Error

The error type returned by Quote::escape.

Formatter

The type passed between calls to Quote::escape.

Traits

Quote

The trait used to quote strings.

Type Definitions

Result

The type returned by Quote::escape.