pthorpe92 / ansiterm-clone Goto Github PK

ogham/rust-ansi-term#59

I'm trying to migrate my project from using colored to ansi_term, as one of my dependencies already uses the latter. I was expecting this to be a straightforward replacement, but faced an issue: the Display implementation in ansi_term seems to ignore the formatting settings, e.g. with the following code

const DIGITS: &'static str = "1234567890";

fn main() { 
    let s = Color::Red.paint(DIGITS);
    println!("{:.5}", s);
}

the expected behavior is: the provided format string is used; red string 12345 is printed;
the actual behavior is: the formatting settings are ignored; red string 1234567890 is printed.

Is this intentional, or a bug?

rustc: 1.38.0
ansi_term: 0.12.1

This issue looks pretty hairy, although there does seem to be commits/ merged PR's in other forks that we can look into to see how it is solved.

ogham/rust-ansi-term#64

Right now the paint function on Style and Color only accepts

I where
    I: Into<Cow<'a, S>>,
    <S as ToOwned>::Owned: Debug,

But in the documents it notes that the paint function doesn't do allocations and return the string with the color applied, instead it returns a Display type which wraps the original string. It seems like this restriction could be relaxed without making a breaking change.

Ideally I'd like it to return a type that impls Display if the inner type impls display, and impls Debug if the inner type impls Debug, which would let me write code like this:

                write!(
                    f,
                    "\n{}",
                    Style::new().bold().paint(format_args!(
                        "{:>8} > {}",
                        cur_line_no,
                        line.unwrap()
                    ))
                )?;

instead of what I have to write right now

                write!(
                    f,
                    "\n{:>8}{}{}",
                    bold.paint(cur_line_no.to_string()),
                    bold.paint(" > "),
                    bold.paint(line.unwrap())
                )?;

It would also make it easier to work with error reporting:

        for (n, error) in errors {
            writeln!(f)?;
            write!(Indented::numbered(f, n), "{}", Red.paint(error))?;
        }

instead of:

        let mut buf = String::new();
        for (n, error) in errors {
            writeln!(f)?;
            buf.clear();
            write!(&mut buf, "{}", error).unwrap();
            write!(Indented::numbered(f, n), "{}", Red.paint(&buf))?;
        }

I see many projects using this library, and I don't see simple way to disable colored output for those apps (without code modification). In production environments I like to grep easily logs and colors are making it super difficult.

More info about NO_COLOR environment variable at https://no-color.org/

This is a valid issue, and should be looked into