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#### Context When tree-sitter parses a file with broken syntax (e.g. a large partial SQL `VALUES` clause, or any language where a large chunk becomes invalid), it can produce a single `ERROR` node spanning thousands of lines. On every render frame, Zed queries this tree for syntax highlights via `SyntaxMapCaptures`. Previously, only `set_byte_range` was applied to the query cursor - this limits which captures are *returned*, but tree-sitter still had to *traverse* the entire ERROR subtree to find them, causing O(file size) work per frame and making scrolling/editing visibly laggy. The fix applies `set_containing_byte_range` to the highlight query cursor, mirroring what `SyntaxMapMatches` already does for indentation and bracket queries. This tells tree-sitter to skip subtrees that extend far beyond the visible window, reducing traversal to the visible range only. **Note:** This fix eliminates the main freeze/stall caused by full-tree traversal. A small amount of lag may still occur on very large broken files, as tree-sitter still needs to parse the error-recovery structure. Further improvements would require deeper changes to tree-sitter's query execution or incremental parsing. #### Closes #52390 #### How to Review Small change — focus on [syntax_map.rs:1119-1123](crates/language/src/syntax_map.rs#L1119) (the fix) and the `containing_byte_range_for_captures` helper below it. Compare with the existing `SyntaxMapMatches::new` path (line ~1255) which uses the same pattern. #### Self-Review Checklist - [x] I've reviewed my own diff for quality, security, and reliability - [x] Unsafe blocks (if any) have justifying comments - [x] The content is consistent with the [UI/UX checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist) - [x] Tests cover the new/changed behavior - [x] Performance impact has been considered and is acceptable #### Video [Screencast from 2026-03-26 14-19-19.webm](https://github.com/user-attachments/assets/6628492a-f013-438a-836a-2740f6e2f266) #### Note : Reopens previous work from closed PR #52475 (fork was deleted) Release Notes: - Fixed laggy scrolling and editing in files with large broken syntax regions (e.g. incomplete SQL `VALUES` clauses or large invalid blocks in any language) --------- Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com> |
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