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-rw-r--r--helix-core/src/syntax.rs23
1 files changed, 23 insertions, 0 deletions
diff --git a/helix-core/src/syntax.rs b/helix-core/src/syntax.rs
index 0f62577f..b320fcda 100644
--- a/helix-core/src/syntax.rs
+++ b/helix-core/src/syntax.rs
@@ -354,6 +354,25 @@ impl<'a> CapturedNode<'a> {
}
}
+/// The number of matches a TS cursor can at once to avoid performance problems for medium to large files.
+/// Set with `set_match_limit`.
+/// Using such a limit means that we lose valid captures in, so there is fundamentally a tradeoff here.
+///
+///
+/// Old tree sitter versions used a limit of 32 by default until this limit was removed in version `0.19.5` (must now be set manually).
+/// However, this causes performance issues for medium to large files.
+/// In helix, this problem caused treesitter motions to take multiple seconds to complete in medium-sized rust files (3k loc).
+/// Neovim also encountered this problem and reintroduced this limit after it was removed upstream
+/// (see <https://github.com/neovim/neovim/issues/14897> and <https://github.com/neovim/neovim/pull/14915>).
+/// The number used here is fundamentally a tradeoff between breaking some obscure edge cases and performance.
+///
+///
+/// A value of 64 was chosen because neovim uses that value.
+/// Neovim chose this value somewhat arbitrarily (<https://github.com/neovim/neovim/pull/18397>) adjusting it whenever issues occur in practice.
+/// However this value has been in use for a long time and due to the large userbase of neovim it is probably a good choice.
+/// If this limit causes problems for a grammar in the future, it could be increased.
+const TREE_SITTER_MATCH_LIMIT: u32 = 64;
+
impl TextObjectQuery {
/// Run the query on the given node and return sub nodes which match given
/// capture ("function.inside", "class.around", etc).
@@ -394,6 +413,8 @@ impl TextObjectQuery {
.iter()
.find_map(|cap| self.query.capture_index_for_name(cap))?;
+ cursor.set_match_limit(TREE_SITTER_MATCH_LIMIT);
+
let nodes = cursor
.captures(&self.query, node, RopeProvider(slice))
.filter_map(move |(mat, _)| {
@@ -843,6 +864,7 @@ impl Syntax {
let mut cursor = ts_parser.cursors.pop().unwrap_or_else(QueryCursor::new);
// TODO: might need to set cursor range
cursor.set_byte_range(0..usize::MAX);
+ cursor.set_match_limit(TREE_SITTER_MATCH_LIMIT);
let source_slice = source.slice(..);
@@ -1032,6 +1054,7 @@ impl Syntax {
// if reusing cursors & no range this resets to whole range
cursor_ref.set_byte_range(range.clone().unwrap_or(0..usize::MAX));
+ cursor_ref.set_match_limit(TREE_SITTER_MATCH_LIMIT);
let mut captures = cursor_ref
.captures(