Simplify first-in-line computation for indent queries. (helix-editor#…

…10527)

helix-core/src/indent.rs

@@ -247,41 +247,18 @@ fn add_indent_level(
  }
 }
 
-/// Computes for node and all ancestors whether they are the first node on their line.
-/// The first entry in the return value represents the root node, the last one the node itself
-fn get_first_in_line(mut node: Node, new_line_byte_pos: Option<usize>) -> Vec<bool> {
- let mut first_in_line = Vec::new();
- loop {
- if let Some(prev) = node.prev_sibling() {
- // If we insert a new line, the first node at/after the cursor is considered to be the first in its line
- let first = prev.end_position().row != node.start_position().row
- || new_line_byte_pos.map_or(false, |byte_pos| {
- node.start_byte() >= byte_pos && prev.start_byte() < byte_pos
- });
- first_in_line.push(Some(first));
- } else {
- // Nodes that have no previous siblings are first in their line if and only if their parent is
- // (which we don't know yet)
- first_in_line.push(None);
- }
- if let Some(parent) = node.parent() {
- node = parent;
- } else {
- break;
- }
- }
-
- let mut result = Vec::with_capacity(first_in_line.len());
- let mut parent_is_first = true; // The root node is by definition the first node in its line
- for first in first_in_line.into_iter().rev() {
- if let Some(first) = first {
- result.push(first);
- parent_is_first = first;
- } else {
- result.push(parent_is_first);
+/// Return true if only whitespace comes before the node on its line.
+/// If given, new_line_byte_pos is treated the same way as any existing newline.
+fn is_first_in_line(node: Node, text: RopeSlice, new_line_byte_pos: Option<usize>) -> bool {
+ let mut line_start_byte_pos = text.line_to_byte(node.start_position().row);
+ if let Some(pos) = new_line_byte_pos {
+ if line_start_byte_pos < pos && pos <= node.start_byte() {
+ line_start_byte_pos = pos;
  }
  }
- result
+ text.byte_slice(line_start_byte_pos..node.start_byte())
+ .chars()
+ .all(|c| c.is_whitespace())
 }
 
 /// The total indent for some line of code.
@@ -852,7 +829,6 @@ pub fn treesitter_indent_for_pos<'a>(
  byte_pos,
  new_line_byte_pos,
  )?;
- let mut first_in_line = get_first_in_line(node, new_line.then_some(byte_pos));
 
  let mut result = Indentation::default();
  // We always keep track of all the indent changes on one line, in order to only indent once
@@ -861,9 +837,7 @@ pub fn treesitter_indent_for_pos<'a>(
  let mut indent_for_line_below = Indentation::default();
 
  loop {
- // This can safely be unwrapped because `first_in_line` contains
- // one entry for each ancestor of the node (which is what we iterate over)
- let is_first = *first_in_line.last().unwrap();
+ let is_first = is_first_in_line(node, text, new_line_byte_pos);
 
  // Apply all indent definitions for this node.
  // Since we only iterate over each node once, we can remove the
@@ -906,7 +880,6 @@ pub fn treesitter_indent_for_pos<'a>(
  }
 
  node = parent;
- first_in_line.pop();
  } else {
  // Only add the indentation for the line below if that line
  // is not after the line that the indentation is calculated for.