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diff: keep absolute ranges to support unchanged regions of different lengths

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We have two options to achieve "diff --ignore-*-space":
 a. preprocess contents to be diffed, then translate hunk ranges back
 b. add hooks to customize eq and hash functions
I originally thought (a) would be easier, but actually, there aren't many
changes needed to implement (b). And (b) should have a fewer logic errors.

This patch removes assumption that each unchanged region has the same content
length. It won't be true if whitespace characters are ignored.
This commit is contained in:
Yuya Nishihara 2024-09-22 10:26:39 +09:00
parent e28fdac48e
commit 4f8ae69367
1 changed files with 25 additions and 39 deletions
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64
lib/src/diff.rs
View file

@ -343,7 +343,7 @@ fn intersect_unchanged_words(
#[derive(Clone, PartialEq, Eq, Debug)]
struct UnchangedRange {
base: Range<usize>,
offsets: Vec<isize>,
others: Vec<Range<usize>>,
}
impl UnchangedRange {
@ -356,22 +356,10 @@ impl UnchangedRange {
) -> Self {
assert_eq!(other_sources.len(), other_positions.len());
let base = base_source.range_at(base_position);
let offsets = iter::zip(other_sources, other_positions)
.map(|(source, pos)| {
let other_range = source.range_at(*pos);
assert_eq!(base.len(), other_range.len());
other_range.start.wrapping_sub(base.start) as isize
})
let others = iter::zip(other_sources, other_positions)
.map(|(source, pos)| source.range_at(*pos))
.collect();
UnchangedRange { base, offsets }
}
fn start(&self, side: usize) -> usize {
self.base.start.wrapping_add(self.offsets[side] as usize)
}
fn end(&self, side: usize) -> usize {
self.base.end.wrapping_add(self.offsets[side] as usize)
UnchangedRange { base, others }
}
}
@ -396,9 +384,6 @@ impl Ord for UnchangedRange {
pub struct Diff<'input> {
base_input: &'input BStr,
other_inputs: Vec<&'input BStr>,
// The key is a range in the base input. The value is the start of each non-base region
// relative to the base region's start. By making them relative, they don't need to change
// when the base range changes.
unchanged_regions: Vec<UnchangedRange>,
}
@ -450,7 +435,7 @@ impl<'input> Diff<'input> {
[] => {
let whole_range = UnchangedRange {
base: 0..base_source.text.len(),
offsets: vec![],
others: vec![],
};
vec![whole_range]
}
@ -499,13 +484,12 @@ impl<'input> Diff<'input> {
}
};
// Add an empty range at the end to make life easier for hunks().
let offsets = other_inputs
.iter()
.map(|input| input.len().wrapping_sub(base_input.len()) as isize)
.collect_vec();
unchanged_regions.push(UnchangedRange {
base: base_input.len()..base_input.len(),
offsets,
others: other_inputs
.iter()
.map(|input| input.len()..input.len())
.collect(),
});
let mut diff = Self {
@ -543,12 +527,11 @@ impl<'input> Diff<'input> {
}
pub fn hunks<'diff>(&'diff self) -> DiffHunkIterator<'diff, 'input> {
let previous_offsets = vec![0; self.other_inputs.len()];
DiffHunkIterator {
diff: self,
previous: UnchangedRange {
base: 0..0,
offsets: previous_offsets,
others: vec![0..0; self.other_inputs.len()],
},
unchanged_emitted: true,
unchanged_iter: self.unchanged_regions.iter(),
@ -563,10 +546,8 @@ impl<'input> Diff<'input> {
) -> impl Iterator<Item = &'input BStr> + 'a {
itertools::chain(
iter::once(&self.base_input[previous.base.end..current.base.start]),
(0..current.offsets.len()).map(|i| {
let changed_range = previous.end(i)..current.start(i);
&self.other_inputs[i][changed_range]
}),
itertools::izip!(&self.other_inputs, &previous.others, &current.others)
.map(|(input, prev, cur)| &input[prev.end..cur.start]),
)
}
@ -575,7 +556,7 @@ impl<'input> Diff<'input> {
pub fn refine_changed_regions(&mut self, tokenizer: impl Fn(&[u8]) -> Vec<Range<usize>>) {
let mut previous = UnchangedRange {
base: 0..0,
offsets: vec![0; self.other_inputs.len()],
others: vec![0..0; self.other_inputs.len()],
};
let mut new_unchanged_ranges = vec![];
for current in self.unchanged_regions.iter() {
@ -585,15 +566,15 @@ impl<'input> Diff<'input> {
// (`self`).
let refined_diff =
Diff::for_tokenizer(self.hunk_between(&previous, current), &tokenizer);
for refined in refined_diff.unchanged_regions {
for refined in &refined_diff.unchanged_regions {
let new_base_start = refined.base.start + previous.base.end;
let new_base_end = refined.base.end + previous.base.end;
let offsets = iter::zip(refined.offsets, &previous.offsets)
.map(|(refi, prev)| refi + prev)
.collect_vec();
let new_others = iter::zip(&refined.others, &previous.others)
.map(|(refi, prev)| (refi.start + prev.end)..(refi.end + prev.end))
.collect();
new_unchanged_ranges.push(UnchangedRange {
base: new_base_start..new_base_end,
offsets,
others: new_others,
});
}
previous = current.clone();
@ -612,10 +593,15 @@ impl<'input> Diff<'input> {
let mut maybe_previous: Option<UnchangedRange> = None;
for current in self.unchanged_regions.iter() {
if let Some(previous) = maybe_previous {
if previous.base.end == current.base.start && previous.offsets == *current.offsets {
if previous.base.end == current.base.start
&& iter::zip(&previous.others, &current.others)
.all(|(prev, cur)| prev.end == cur.start)
{
maybe_previous = Some(UnchangedRange {
base: previous.base.start..current.base.end,
offsets: current.offsets.clone(),
others: iter::zip(&previous.others, &current.others)
.map(|(prev, cur)| prev.start..cur.end)
.collect(),
});
continue;
}