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correctly map unsorted positions (helix-editor#7471)
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* correctly map unsorted positions

* Fix typo

Co-authored-by: Michael Davis <mcarsondavis@gmail.com>

---------

Co-authored-by: Michael Davis <mcarsondavis@gmail.com>
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@pascalkuthe @the-mikedavis
2 people authored and Schuyler Mortimer committed Jul 10, 2024
1 parent e74ba98 commit 0919a83
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Showing 2 changed files with 95 additions and 37 deletions.
130 changes: 94 additions & 36 deletions helix-core/src/transaction.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -326,7 +326,7 @@ impl ChangeSet {
self.changes.is_empty() || self.changes == [Operation::Retain(self.len)]
}

/// Map a *sorted* list of positions through the changes.
/// Map a (mostly) *sorted* list of positions through the changes.
///
/// This is equivalent to updating each position with `map_pos`:
///
Expand All @@ -335,27 +335,63 @@ impl ChangeSet {
/// *pos = changes.map_pos(*pos, assoc);
/// }
/// ```
/// However this function is significantly faster running in `O(N+M)` instead of `O(NM)`
/// However this function is significantly faster for sorted lists running
/// in `O(N+M)` instead of `O(NM)`. This function also handles unsorted/
/// partially sorted lists. However, in that case worst case complexity is
/// again `O(MN)`. For lists that are often/mostly sorted (like the end of diagnostic ranges)
/// performance is usally close to `O(N + M)`
pub fn update_positions<'a>(&self, positions: impl Iterator<Item = (&'a mut usize, Assoc)>) {
use Operation::*;

let mut positions = positions.peekable();
macro_rules! map {
($map: expr) => {
loop {
let Some((pos, assoc)) = positions.peek_mut() else { return; };
let Some(new_pos) = $map(**pos, *assoc) else { break; };
**pos = new_pos;
positions.next();
}
};
}

let mut old_pos = 0;
let mut new_pos = 0;
let mut iter = self.changes.iter().peekable();
let mut iter = self.changes.iter().enumerate().peekable();

'outer: loop {
macro_rules! map {
($map: expr, $i: expr) => {
loop {
let Some((pos, assoc)) = positions.peek_mut() else { return; };
if **pos < old_pos {
// Positions are not sorted, revert to the last Operation that
// contains this position and continue iterating from there.
// We can unwrap here since `pos` can not be negative
// (unsigned integer) and iterating backwards to the start
// should always move us back to the start
for (i, change) in self.changes[..$i].iter().enumerate().rev() {
match change {
Retain(i) => {
old_pos -= i;
new_pos -= i;
}
Delete(i) => {
old_pos -= i;
}
Insert(ins) => {
new_pos -= ins.chars().count();
}
}
if old_pos <= **pos {
iter = self.changes[i..].iter().enumerate().peekable();
}
}
debug_assert!(old_pos <= **pos, "Reverse Iter across changeset works");
continue 'outer;
}
let Some(new_pos) = $map(**pos, *assoc) else { break; };
**pos = new_pos;
positions.next();
}
};
}

let Some((i, change)) = iter.next() else {
map!(|pos, _| (old_pos == pos).then_some(new_pos), self.changes.len());
break;
};

while let Some(change) = iter.next() {
let len = match change {
Delete(i) | Retain(i) => *i,
Insert(_) => 0,
Expand All @@ -364,50 +400,58 @@ impl ChangeSet {

match change {
Retain(_) => {
map!(|pos, _| (old_end > pos).then_some(new_pos + (pos - old_pos)));
map!(
|pos, _| (old_end > pos).then_some(new_pos + (pos - old_pos)),
i
);
new_pos += len;
}
Delete(_) => {
// in range
map!(|pos, _| (old_end > pos).then_some(new_pos));
map!(|pos, _| (old_end > pos).then_some(new_pos), i);
}
Insert(s) => {
let ins = s.chars().count();

// a subsequent delete means a replace, consume it
if let Some(Delete(len)) = iter.peek() {
if let Some((_, Delete(len))) = iter.peek() {
iter.next();

old_end = old_pos + len;
// in range of replaced text
map!(|pos, assoc| (old_end > pos).then(|| {
// at point or tracking before
if pos == old_pos || assoc == Assoc::Before {
new_pos
} else {
// place to end of insert
new_pos + ins
}
}));
map!(
|pos, assoc| (old_end > pos).then(|| {
// at point or tracking before
if pos == old_pos || assoc == Assoc::Before {
new_pos
} else {
// place to end of insert
new_pos + ins
}
}),
i
);
} else {
// at insert point
map!(|pos, assoc| (old_pos == pos).then(|| {
// return position before inserted text
if assoc == Assoc::Before {
new_pos
} else {
// after text
new_pos + ins
}
}));
map!(
|pos, assoc| (old_pos == pos).then(|| {
// return position before inserted text
if assoc == Assoc::Before {
new_pos
} else {
// after text
new_pos + ins
}
}),
i
);
}

new_pos += ins;
}
}
old_pos = old_end;
}
map!(|pos, _| (old_pos == pos).then_some(new_pos));
let out_of_bounds: Vec<_> = positions.collect();

panic!("Positions {out_of_bounds:?} are out of range for changeset len {old_pos}!",)
Expand Down Expand Up @@ -822,6 +866,20 @@ mod test {
};
assert_eq!(cs.map_pos(2, Assoc::Before), 2);
assert_eq!(cs.map_pos(2, Assoc::After), 2);
// unsorted selection
let cs = ChangeSet {
changes: vec![
Insert("ab".into()),
Delete(2),
Insert("cd".into()),
Delete(2),
],
len: 4,
len_after: 4,
};
let mut positions = [4, 2];
cs.update_positions(positions.iter_mut().map(|pos| (pos, Assoc::After)));
assert_eq!(positions, [4, 2]);
}

#[test]
Expand Down
2 changes: 1 addition & 1 deletion helix-view/src/document.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1197,7 +1197,7 @@ impl Document {
if let Some(data) = Rc::get_mut(annotations) {
changes.update_positions(
data.iter_mut()
.map(|diagnostic| (&mut diagnostic.char_idx, Assoc::After)),
.map(|annotation| (&mut annotation.char_idx, Assoc::After)),
);
}
};
Expand Down

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