indenter

A few wrappers for the fmt::Write objects that efficiently appends and remove common indentation after every newline

Setup

Add this to your Cargo.toml:

[dependencies]
indenter = "0.2"

Examples

Indentation only

This type is intended primarily for writing error reporters that gracefully format error messages that span multiple lines.

use std::error::Error;
use std::fmt::{self, Write};
use indenter::indented;

struct ErrorReporter<'a>(&'a dyn Error);

impl fmt::Debug for ErrorReporter<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let mut source = Some(self.0);
        let mut i = 0;

        while let Some(error) = source {
            writeln!(f)?;
            write!(indented(f).ind(i), "{}", error)?;

            source = error.source();
            i += 1;
        }

        Ok(())
    }
}

“Dedenting” (removing common leading indendation)

This type is intended primarily for formatting source code. For example, when generating code.

This type requires the feature std.

use std::error::Error;
use core::fmt::{self, Write};
use indenter::CodeFormatter;

let mut output = String::new();
let mut f = CodeFormatter::new(&mut output, "    ");

write!(
    f,
    r#"
    Hello
        World
    "#,
);

assert_eq!(output, "Hello\n    World\n");

let mut output = String::new();
let mut f = CodeFormatter::new(&mut output, "    ");

// it can also indent...
f.indent(2);

write!(
    f,
    r#"
    Hello
        World
    "#,
);

assert_eq!(output, "        Hello\n            World\n");

License