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perf(tspath): optimize the fast path case for ToFileNameLowerCase #1558

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Merged
merged 3 commits into from
Aug 12, 2025
Merged

perf(tspath): optimize the fast path case for ToFileNameLowerCase #1558

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8ffae86
perf(tspath): optimize the fast path case for `ToFileNameLowerCase`
camc314 Aug 11, 2025
2462166
lint
camc314 Aug 11, 2025
dcb78e8
rename fn arg from `s` to `fileName`
camc314 Aug 12, 2025
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29 changes: 28 additions & 1 deletion internal/tspath/path.go
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Original file line number Diff line number Diff line change
Expand Up @@ -534,8 +534,35 @@ func GetCanonicalFileName(fileName string, useCaseSensitiveFileNames bool) strin
// they have corresponding upper case character so they dont need special handling

func ToFileNameLowerCase(fileName string) string {
const IWithDot = '\u0130'

ascii := true
needsLower := false
for _, c := range []byte(fileName) {
if c >= 0x80 {
ascii = false
break
}
if 'A' <= c && c <= 'Z' {
needsLower = true
}
}
if ascii {
if !needsLower {
return fileName
}
b := make([]byte, len(fileName))
for i, c := range []byte(fileName) {
if 'A' <= c && c <= 'Z' {
c += 'a' - 'A' // +32
}
b[i] = c
}
return string(b)
}

return strings.Map(func(r rune) rune {
if r == '\u0130' {
if r == IWithDot {
return r
}
return unicode.ToLower(r)
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