From e985466556c71743ec9f47ee969bb4f45da141aa Mon Sep 17 00:00:00 2001 From: Yuan Fu Date: Sat, 18 Feb 2023 02:20:12 -0800 Subject: [PATCH] Fix comment in treesit_record_change (bug#61369) Turns out the previous commit message and comment is not entirely correct: the old behavior is in fact wrong, not just "correct but has problems". Here is why the old code is wrong: |visible range| -> markup for visible range updated range -> markup for updated range ------------- First we have some text |aaaaaa| Now we insert something at the beginning, because we clip new_end_offset to visible_end, out of eight b's inserted, only the first six are known to tree-sitter. |bbbbbbbbaaaa|aa start: 0, old_end: 0, new_end: 6 ------ In treesit_sync_visible_region, we sync up visible region, but the two missing b's are not in the updated range. |bbbbbbbbaaaaaa| start: 12, old_end: 12, new_end: 14 -- The old behavior not only is wrong, but also doesn't make much sense. * src/treesit.c (treesit_record_change): Update comment. --- src/treesit.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/src/treesit.c b/src/treesit.c index e1d6f1ef79f..ef0f2407840 100644 --- a/src/treesit.c +++ b/src/treesit.c @@ -797,12 +797,10 @@ treesit_record_change (ptrdiff_t start_byte, ptrdiff_t old_end_byte, max (visible_beg, old_end_byte)) - visible_beg); /* We don't clip new_end_offset under visible_end, because - inserting in narrowed region always extends the visible - region. If we clip new_end_offset here, and re-add the - clipped "tail" in treesit_sync_visible_region later, - while it is technically equivalent, tree-sitter's - incremental parsing algorithm doesn't seem to like it - (bug#61369). */ + otherwise we would miss updating the clipped part. Plus, + when inserting in narrowed region, the narrowed region + will grow to accommodate the new text, so this is the + correct behavior. (Bug#61369). */ ptrdiff_t new_end_offset = (max (visible_beg, new_end_byte) - visible_beg); eassert (start_offset <= old_end_offset); -- 2.39.5