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Match literal at end of sub-character substring #910

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Merged
natecook1000 merged 2 commits into from
Oct 26, 2026
Merged

Match literal at end of sub-character substring #910

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2f402eb
Match literal at end of sub-character substring
natecook1000 Oct 26, 2026
f74203b
Merge branch 'main' into fix/substring-sub-character-end
natecook1000 Oct 26, 2026
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4 changes: 2 additions & 2 deletions Sources/_StringProcessing/Engine/Processor.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -799,7 +799,7 @@ extension String {
let idx = unicodeScalars.index(after: pos)
assert(idx <= end, "Input is a substring with a sub-scalar endIndex.")

if boundaryCheck && !isOnGraphemeClusterBoundary(idx) {
if boundaryCheck && idx != end && !isOnGraphemeClusterBoundary(idx) {
return nil
}

Expand All @@ -820,7 +820,7 @@ extension String {

guard cur <= end else { return nil }

if boundaryCheck && !isOnGraphemeClusterBoundary(cur) {
if boundaryCheck && cur != end && !isOnGraphemeClusterBoundary(cur) {
return nil
}

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12 changes: 12 additions & 0 deletions Tests/RegexTests/MatchTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -3059,6 +3059,18 @@ extension RegexTests {
XCTAssertNotNil("tesTs".wholeMatch(of: regex))
}

func testLiteralAtSubCharacterEnd() throws {
let cafe = "cafe\u{301}"
let sub = cafe[..<cafe.unicodeScalars.index(before: cafe.endIndex)]
for regex in [#/afe/#, #/af./#] {
XCTAssertEqual(sub.firstMatch(of: regex)?.0, "afe")
}
XCTAssertNotNil(sub.firstRange(of: "afe"))

// No match for a literal ending sub-character
XCTAssertNil(cafe.firstRange(of: Regex<Substring>(verbatim: "afe")))
}

func testAutoPossessificationSkippedNodes() throws {
firstMatchTest(#"(\w* {0})a"#, input: "a", match: "a")
firstMatchTest(#"((\w* {0})){1}()a"#, input: "a", match: "a")
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