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Bump tree-sitter pattern matching limit to 256 #4830

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Nov 21, 2022
Merged

Bump tree-sitter pattern matching limit to 256 #4830

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17 changes: 9 additions & 8 deletions helix-core/src/syntax.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -354,24 +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.
/// The maximum number of in-progress matches a TS cursor can consider at once.
/// This is set to a constant in order to avoid performance problems for medium to large files. Set with `set_match_limit`.
/// Using such a limit means that we lose valid captures, 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;
/// Neovim chose 64 for this value somewhat arbitrarily (<https://github.com/neovim/neovim/pull/18397>).
/// 64 is too low for some languages though. In particular, it breaks some highlighting for record fields in Erlang record definitions.
/// This number can be increased if new syntax highlight breakages are found, as long as the performance penalty is not too high.
const TREE_SITTER_MATCH_LIMIT: u32 = 256;

impl TextObjectQuery {
/// Run the query on the given node and return sub nodes which match given
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