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Fix to implements in-place stdx::replace #20706

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Merged
merged 2 commits into from
Sep 20, 2025
+41 −3
Merged

Fix to implements in-place stdx::replace #20706

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48dc150
Fix to implements in-place stdx::replace
A4-Tacks Sep 20, 2025
29de96c
Add some test for stdx::replace
A4-Tacks Sep 20, 2025
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44 changes: 41 additions & 3 deletions crates/stdx/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -187,11 +187,19 @@ pub fn is_upper_snake_case(s: &str) -> bool {
}

pub fn replace(buf: &mut String, from: char, to: &str) {
if !buf.contains(from) {
let replace_count = buf.chars().filter(|&ch| ch == from).count();
if replace_count == 0 {
return;
}
// FIXME: do this in place.
*buf = buf.replace(from, to);
let from_len = from.len_utf8();
let additional = to.len().saturating_sub(from_len);
buf.reserve(additional * replace_count);

let mut end = buf.len();
while let Some(i) = buf[..end].rfind(from) {
buf.replace_range(i..i + from_len, to);
end = i;
}
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@ShoyuVanilla ShoyuVanilla Sep 20, 2025 •
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The implementation looks great. But seems that we don't have any test for this function so far. Could we have a simple test for this?

}

#[must_use]
Expand Down Expand Up @@ -343,4 +351,34 @@ mod tests {
"fn main() {\n return 92;\n}\n"
);
}

#[test]
fn test_replace() {
#[track_caller]
fn test_replace(src: &str, from: char, to: &str, expected: &str) {
let mut s = src.to_owned();
replace(&mut s, from, to);
assert_eq!(s, expected, "from: {from:?}, to: {to:?}");
}

test_replace("", 'a', "b", "");
test_replace("", 'a', "😀", "");
test_replace("", '😀', "a", "");
test_replace("a", 'a', "b", "b");
test_replace("aa", 'a', "b", "bb");
test_replace("ada", 'a', "b", "bdb");
test_replace("a", 'a', "😀", "😀");
test_replace("😀", '😀', "a", "a");
test_replace("😀x", '😀', "a", "ax");
test_replace("y😀x", '😀', "a", "yax");
test_replace("a,b,c", ',', ".", "a.b.c");
test_replace("a,b,c", ',', "..", "a..b..c");
test_replace("a.b.c", '.', "..", "a..b..c");
test_replace("a.b.c", '.', "..", "a..b..c");
test_replace("a😀b😀c", '😀', ".", "a.b.c");
test_replace("a.b.c", '.', "😀", "a😀b😀c");
test_replace("a.b.c", '.', "😀😀", "a😀😀b😀😀c");
test_replace(".a.b.c.", '.', "()", "()a()b()c()");
test_replace(".a.b.c.", '.', "", "abc");
}
}
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