fix: prevent panic in search highlighting on multibyte text#66
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buildSnippet sliced snippets at fixed byte offsets without respecting UTF-8 rune boundaries, which could split multibyte characters (e.g. Korean) and produce invalid UTF-8. highlightMatches then lowercased that text for matching, and Go's invalid-byte-to-U+FFFD substitution could make the lowercased string longer than the original, causing highlight spans computed against it to overrun the original text and panic on slice-bounds-out-of-range. Snap snippet boundaries to rune starts, and clamp highlight spans against the actual text length before slicing.
jinsekim
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Kairo-Kim
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Jul 13, 2026
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Summary
buildSnippetsliced search snippets at fixed byte offsets (firstMatch ± 40/80) without respecting UTF-8 rune boundaries, which could split a multibyte character (e.g. Korean) in half and produce invalid UTF-8.highlightMatchesthen calledstrings.ToLoweron that invalid text; Go's invalid-byte → U+FFFD substitution can make the lowercased string longer than the original in byte length.text, so a span's end could exceedlen(text), causingpanic: runtime error: slice bounds out of range.Fix
buildSnippet: snapstart/endto the nearest rune boundary viautf8.RuneStartbefore slicing.highlightMatches: clamp each span againstlen(text)(and the running cursor) before slicing, guarding against any remaining case-folding length divergence (e.g. Turkish İ, German ẞ).Test plan
TestBuildSnippet_MultibyteBoundary— exercises snippet building around Korean text at every byte offset.TestHighlightMatches_NoPanicOnCaseFoldLengthChange— Turkish İ case-folding length change, asserts no panic.go build ./...,go vet ./...,go test ./...all pass.