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use super::*;
pub(crate) trait PositionExt {
fn point(&self, document: &Document) -> Point;
}
impl PositionExt for lsp::Position {
/// LSP positions use a zero-based line index for `line` and a UTF-16
/// code-unit offset within that line for `character`.
///
/// Ropey and Tree-sitter, however, operate on UTF-8 byte offsets. To bridge
/// this mismatch, we take the line number directly as the Tree-sitter `row`,
/// then look up the corresponding line in the Rope and convert the UTF-16
/// `character` offset into a char index and, from there, into a UTF-8 byte
/// offset for the `column`.
///
/// The resulting `(row, column)` byte position is then used to locate the
/// node in the syntax tree.
fn point(&self, document: &Document) -> Point {
let row =
usize::try_from(self.line).expect("line index exceeds usize::MAX");
let line = document.content.line(row);
let utf16_cu = usize::try_from(self.character)
.expect("character index exceeds usize::MAX");
Point {
row,
column: line.char_to_byte(line.utf16_cu_to_char(utf16_cu)),
}
}
}
#[cfg(test)]
mod tests {
use {super::*, pretty_assertions::assert_eq};
#[test]
fn converts_utf16_offsets_to_utf8_columns() {
let document = Document::from("a🧪b");
let position = lsp::Position {
line: 0,
character: 3,
};
let point = position.point(&document);
assert_eq!(point, Point { row: 0, column: 5 });
}
}