fix: restrict case-insensitive search to ASCII - #1159
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Case-insensitive matching previously lowercased the full target string before searching. For some Unicode runes, this changes the byte length of the string, so the returned match offsets no longer point to the original text and can highlight the wrong bytes. This patch limits case-insensitive matching to ASCII-only input, where lower/upper conversion is byte-stable and safe. Non-ASCII text keeps the existing behavior instead of relying on Unicode lowercasing that can change offset positions. This is a reference implementation for discussion and is not intended to be merged as-is.
noborus
marked this pull request as draft
August 18, 2026 13:02
- replace expensive strings.ToLower/ToUpper check with ASCII fast-path - limit lowercase conversion to ASCII alphabetic characters - add regression tests for case-insensitive detection
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This changes the behavior, so I decided to close it after all. |
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Case-insensitive matching previously lowercased the full target string before searching. For some Unicode runes, this changes the byte length of the string, so the returned match offsets no longer point to the original text and can highlight the wrong bytes.
This patch limits case-insensitive matching to ASCII-only input, where lower/upper conversion is byte-stable and safe. Non-ASCII text keeps the existing behavior instead of relying on Unicode lowercasing that can change offset positions.
This is a reference implementation for discussion and is not intended to be merged as-is.