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Fix split_at (return Result ver.) #455

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Fix split_at (return Result ver.) #455

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9e9176b
Fix: split_at returns Result
kyoheiu Nov 3, 2022
1e60395
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kyoheiu Nov 3, 2022
f17907b
Revert format
kyoheiu Nov 24, 2022
267ce40
Revert format in test section
kyoheiu Nov 24, 2022
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60 changes: 44 additions & 16 deletions src/util.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -228,7 +228,10 @@ impl<'a> Iterator for LinesWithEndings<'a> {
/// the `Vec<(Style, &str)>` returned by `highlight` methods. Look at the source
/// code for `modify_range` for an example usage.
#[allow(clippy::type_complexity)]
pub fn split_at<'a, A: Clone>(v: &[(A, &'a str)], split_i: usize) -> (Vec<(A, &'a str)>, Vec<(A, &'a str)>) {
pub fn split_at<'a, A: Clone>(
v: &[(A, &'a str)],
split_i: usize,
) -> Result<(Vec<(A, &'a str)>, Vec<(A, &'a str)>), std::fmt::Error> {
// This function works by gradually reducing the problem into smaller sub-problems from the front
let mut rest = v;
let mut rest_split_i = split_i;
Expand All @@ -247,15 +250,21 @@ pub fn split_at<'a, A: Clone>(v: &[(A, &'a str)], split_i: usize) -> (Vec<(A, &'
let mut after = Vec::new();
// If necessary, split the token the split falls inside
if !rest.is_empty() && rest_split_i > 0 {
let (sa, sb) = rest[0].1.split_at(rest_split_i);
before.push((rest[0].0.clone(), sa));
after.push((rest[0].0.clone(), sb));
rest = &rest[1..];
// Splitting in the middle of a multibyte character cause panic.
// To avoid it, this function may return Err.
if !rest[0].1.is_char_boundary(rest_split_i) {
return Err(std::fmt::Error);
} else {
let (sa, sb) = rest[0].1.split_at(rest_split_i);
before.push((rest[0].0.clone(), sa));
after.push((rest[0].0.clone(), sb));
rest = &rest[1..];
}
}

after.extend_from_slice(rest);

(before, after)
Ok((before, after))
}

/// Modify part of a highlighted line using a style modifier, useful for highlighting sections of a line.
Expand All @@ -274,13 +283,17 @@ pub fn split_at<'a, A: Clone>(v: &[(A, &'a str)], split_i: usize) -> (Vec<(A, &'
/// let l2 = modify_range(l, 1..6, boldmod);
/// assert_eq!(l2, &[(plain, "a"), (bold, "bc"), (bold, "def"), (plain, "ghi")]);
/// ```
pub fn modify_range<'a>(v: &[(Style, &'a str)], r: Range<usize>, modifier: StyleModifier) -> Vec<(Style, &'a str)> {
let (mut result, in_and_after) = split_at(v, r.start);
let (inside, mut after) = split_at(&in_and_after, r.end - r.start);
pub fn modify_range<'a>(
v: &[(Style, &'a str)],
r: Range<usize>,
modifier: StyleModifier,
) -> Result<Vec<(Style, &'a str)>, std::fmt::Error> {
let (mut result, in_and_after) = split_at(v, r.start)?;
let (inside, mut after) = split_at(&in_and_after, r.end - r.start)?;

result.extend(inside.iter().map(|(style, s)| { (style.apply(modifier), *s)}));
result.append(&mut after);
result
Ok(result)
}

#[cfg(test)]
Expand Down Expand Up @@ -309,25 +322,40 @@ mod tests {
#[test]
fn test_split_at() {
let l: &[(u8, &str)] = &[];
let (before, after) = split_at(l, 0); // empty
let (before, after) = split_at(l, 0).unwrap(); // empty
assert_eq!((&before[..], &after[..]), (&[][..],&[][..]));

let l = &[(0u8, "abc"), (1u8, "def"), (2u8, "ghi")];

let (before, after) = split_at(l, 0); // at start
let (before, after) = split_at(l, 0).unwrap(); // at start
assert_eq!((&before[..], &after[..]), (&[][..],&[(0u8, "abc"), (1u8, "def"), (2u8, "ghi")][..]));

let (before, after) = split_at(l, 4); // inside token
let (before, after) = split_at(l, 4).unwrap(); // inside token
assert_eq!((&before[..], &after[..]), (&[(0u8, "abc"), (1u8, "d")][..],&[(1u8, "ef"), (2u8, "ghi")][..]));

let (before, after) = split_at(l, 3); // between tokens
let (before, after) = split_at(l, 3).unwrap(); // between tokens
assert_eq!((&before[..], &after[..]), (&[(0u8, "abc")][..],&[(1u8, "def"), (2u8, "ghi")][..]));

let (before, after) = split_at(l, 9); // just after last token
let (before, after) = split_at(l, 9).unwrap(); // just after last token
assert_eq!((&before[..], &after[..]), (&[(0u8, "abc"), (1u8, "def"), (2u8, "ghi")][..], &[][..]));

let (before, after) = split_at(l, 10); // out of bounds
let (before, after) = split_at(l, 10).unwrap(); // out of bounds
assert_eq!((&before[..], &after[..]), (&[(0u8, "abc"), (1u8, "def"), (2u8, "ghi")][..], &[][..]));

let l = &[(0u8, "こんにちは"), (1u8, "世界"), (2u8, "！")];

let (before, after) = split_at(l, 3).unwrap();

assert_eq!(
(&before[..], &after[..]),
(
&[(0u8, "こ")][..],
&[(0u8, "んにちは"), (1u8, "世界"), (2u8, "！")][..]
)
);

//Splitting in the middle of a multibyte character returns Err
assert!(split_at(l, 4).is_err());
}

#[test]
Expand Down