Add utility function ansi::slice_ansi_str

[remi-dupre]

Hi!

While working on a bug of indicatif (cf. console-rs/indicatif#627), I needed an ANSI-aware slicing method. I think it made more sense to add it in this crate.

/// Slice a `&str` in terms of text width. This means that only the text
/// columns strictly between `start` and `stop` will be kept.
///
/// If a multi-columns character overlaps with the end of the interval it will
/// not be included. In such a case, the result will be less than `end - start`
/// columns wide.
///
/// If non-empty head and tail are specified, they are inserted between the
/// ANSI symbols from truncated bounds and the slice.
///
/// This ensures that escape codes are not screwed up in the process.
pub fn slice_str<'a>(s: &'a str, head: &str, bounds: Range<usize>, tail: &str) -> Cow<'a, str> {
    ...
}

This is a generalisation of truncate_str 😃

[remi-dupre]

This was just a random (new?) clippy lint : these are already u16 🤷

[remi-dupre]

Not related to the MR, but while implementing a less optimized draft of my fix I thought this could spare a few allocs. This is probably not something to care about so I wouldn't mind if you want to revert this for the sake of simplification.

[djc]

Can you avoid let .. else in order to pass the MSRV tests?

[remi-dupre]

Indeed, that should be good now 👍

[remi-dupre]

And format is also a recent-is feature, on it 😬

I'll try to build on 1.56, it didn't work last time I tried it because it fails to resolve regex = "=1.10.3" 😞

EDIT : Ok, got it

[remi-dupre]

Should be good, make test runs with rust 1.56 on my machine 👍

[remi-dupre]

Hi!

I bumped into this while doing some cleanup and I think it might still be useful. So I've rebased it on latest main!

[djc]

I definitely don't want to accept a semver-incompatible change for this. Is there a way to make this compatible?

[remi-dupre]

Hi!

You're right that it would be a shame.

Although I think I made a mistake with semver : I only added a new function without affecting the behavior of the existing, as we're still on unstable scheme 0.x.y this should only affect the last (y) component.

I changed the target version to 0.15.12 and made sure that I didn't modify previously existing test cases 👍

[djc]

Okay, this doesn't currently pass the MSRV jobs in CI, so that's something that will have to be fixed. I'd like a cleaner set of changes for review, with separate commits or PRs for each of these changes:

• clippy fixes
• saving allocations on measure_text_width()
• introducing slice_ansi_str()

Please avoid unrelated changes as much as possible (as such, keep functions/logic in the place as much as possible to minimize the diffs). You can leave the version bumping and changelog to me (note that the CHANGELOG.md file is no longer being used).

[remi-dupre]

Hello mon ami ! 🥖

Those are super relevant comments 👍

1. I've created two smaller MRs for parasitic changes
   a. fix: clippy lint (clippy::unnecessary cast) #247
   b. Implement measure_text_width with no allocation #246
2. Following your advice, I've created another to suggest a fix to the MSRV issue : chore: pin once_cell<1.21 to enforce MSRV #248
3. I've removed version & changelog related diffs

[remi-dupre]

I'm putting this in draft until #250 is solved.

[remi-dupre]

Rebased & ready for review again! 😄