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Fix two byte-index-into-character-slice bugs in Path #13

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Merged
hellerve merged 2 commits into from
Aug 21, 2026
+22 −2
Merged

Fix two byte-index-into-character-slice bugs in Path #13

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ca69b0c
Compare the leading byte in absolute?
Aug 20, 2026
81cb3a3
Cut split-extension on byte indices
Aug 20, 2026
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6 changes: 4 additions & 2 deletions path.carp
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@ variable we use on this OS.")
(def sep-string "\\")
(def escapes? false))
(posix-only
(defn absolute? [p] (String.starts-with? p "/"))
(defn absolute? [p] (and (not (String.empty? p)) (= \/ (String.head p))))
(def separator \/)
(def separators [\/])
(def search-path-separator \:)
Expand Down Expand Up @@ -165,7 +165,9 @@ Examples on POSIX:
(let [i (Pattern.find extension-pat p)]
(if (= -1 i)
(Maybe.Nothing)
(Maybe.Just (Pair.init (prefix p i) (suffix p (inc i)))))))
(Maybe.Just
(Pair.init (String.byte-slice p 0 i)
(String.byte-slice p (inc i) (String.length p)))))))

(doc extension "gets the extension of a file as a `Maybe`.")
(defn extension [p] (Maybe.apply (split-extension p) &(fn [p] @(Pair.b &p))))
Expand Down
18 changes: 18 additions & 0 deletions test/path.carp
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Expand Up @@ -10,6 +10,9 @@
(assert-false test (absolute? "path") "absolute? works on relative paths")
(assert-false test (relative? "/path") "relative? works on absolute paths")
(assert-true test (relative? "path") "relative? works on relative paths")
(assert-false test
(absolute? &(String.from-bytes &[187b]))
"absolute? works on a path that is a lone UTF-8 continuation byte")
(assert-equal test
"file.ext"
&(add-extension "file" "ext")
Expand Down Expand Up @@ -163,6 +166,21 @@
&(Maybe.Just (Pair.init @"file/path.txt.bob" @"fred"))
&(split-extension "file/path.txt.bob.fred")
"split-extension gets last extension")
(assert-equal test
&(Maybe.Just (Pair.init @"ä" @"txt"))
&(split-extension "ä.txt")
"split-extension splits at the dot in a multi-byte filename")
(assert-equal test
&(Maybe.Just (Pair.init @"grüße" @"c"))
&(split-extension "grüße.c")
"split-extension keeps the extension of a multi-byte filename")
(assert-true test
(is-extension? "ä.txt" "txt")
"is-extension? works on a multi-byte filename")
(assert-equal test
&(Maybe.Just (Pair.init (String.from-bytes &[187b 187b]) @""))
&(split-extension &(String.from-bytes &[187b 187b 46b]))
"split-extension works on a path of UTF-8 continuation bytes")
(assert-equal test
"file.ext"
&(replace-extension "file.txt" "ext")
Expand Down