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Fix common_prefix_at panic when needle contains multibyte chars

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Also, make the prefix matching case-insensitive, since this is the
typical behavior with autocomplete.
This commit is contained in:
Max Brunsfeld 2022-04-01 14:49:36 -07:00
parent 6f28033efe
commit 5090e6f146
2 changed files with 57 additions and 27 deletions
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34
crates/text/src/text.rs
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@ -1510,31 +1510,25 @@ impl BufferSnapshot {
pub fn common_prefix_at<T>(&self, position: T, needle: &str) -> Range<T>
where
T: Clone + ToOffset + FromAnchor,
T: ToOffset + TextDimension,
{
let position_offset = position.to_offset(self);
// Get byte indices and char counts for every character in needle in reverse order
let char_indices = needle
let offset = position.to_offset(self);
let common_prefix_len = needle
.char_indices()
.map(|(index, _)| index)
.chain(std::iter::once(needle.len()))
.enumerate()
// Don't test any prefixes that are bigger than the requested position
.take_while(|(_, prefix_length)| *prefix_length <= position_offset);
let start = char_indices
// Compute the prefix string and prefix start location
.map(move |(byte_position, char_length)| {
(position_offset - char_length, &needle[..byte_position])
.chain([needle.len()])
.take_while(|&len| len <= offset)
.filter(|&len| {
let left = self
.chars_for_range(offset - len..offset)
.flat_map(|c| char::to_lowercase(c));
let right = needle[..len].chars().flat_map(|c| char::to_lowercase(c));
left.eq(right)
})
// Only take strings when the prefix is contained at the expected prefix position
.filter(|(prefix_offset, prefix)| self.contains_str_at(prefix_offset, prefix))
// Convert offset to T
.map(|(prefix_offset, _)| T::from_anchor(&self.anchor_before(prefix_offset), self))
.last()
// If no prefix matches, return the passed in position to create an empty range
.unwrap_or(position.clone());
.unwrap_or(0);
let start_offset = offset - common_prefix_len;
let start = self.text_summary_for_range(0..start_offset);
start..position
}