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Use icu4x for casefold() #7780

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Merged
youknowone merged 1 commit into from
May 16, 2026
Merged

Use icu4x for casefold() #7780

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10 changes: 0 additions & 10 deletions Cargo.lock
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1 change: 0 additions & 1 deletion Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -186,7 +186,6 @@ bitflags = "2.11.0"
bitflagset = "0.0.3"
bstr = "1"
bzip2 = "0.6"
caseless = "0.2.2"

@ShaharNaveh ShaharNaveh May 15, 2026

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nice

chrono = { version = "0.4.44", default-features = false, features = ["clock", "std"] }
console_error_panic_hook = "0.1"
constant_time_eq = "0.4"
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1 change: 0 additions & 1 deletion crates/vm/Cargo.toml
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Expand Up @@ -73,7 +73,6 @@ strum_macros = { workspace = true }
thiserror = { workspace = true }
memchr = { workspace = true }

caseless = { workspace = true }
flamer = { workspace = true, optional = true }
half = { workspace = true }
psm = { workspace = true }
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37 changes: 24 additions & 13 deletions crates/vm/src/builtins/str.rs
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Expand Up @@ -45,10 +45,10 @@ use rustpython_common::{
hash,
lock::PyMutex,
str::DeduceStrKind,
wtf8::{CodePoint, Wtf8, Wtf8Buf, Wtf8Chunk, Wtf8Concat},
wtf8::{CodePoint, Wtf8, Wtf8Buf, Wtf8Concat},
};

use icu_casemap::TitlecaseMapper;
use icu_casemap::{CaseMapper, TitlecaseMapper};
use icu_locale::LanguageIdentifier;
use icu_properties::props::{
BidiClass, BinaryProperty, CaseIgnorable, Cased, EnumeratedProperty, GeneralCategory,
Expand Down Expand Up @@ -743,20 +743,31 @@ impl PyStr {
}
}

// casefold is much more aggressive than lower
// Case folding is a Unicode standard operation to erase case differences.
//
// Lower, upper, and title case are special properties. Case folding erases those
// differences. For ASCII, case folding is the same as lower case but other scripts have
// their own, well-defined mappings.
#[pymethod]
fn casefold(&self) -> Self {
match self.as_str_kind() {
PyKindStr::Ascii(s) => caseless::default_case_fold_str(s.as_str()).into(),
PyKindStr::Utf8(s) => caseless::default_case_fold_str(s).into(),
PyKindStr::Wtf8(w) => w
.chunks()
.map(|c| match c {
Wtf8Chunk::Utf8(s) => Wtf8Buf::from_string(caseless::default_case_fold_str(s)),
Wtf8Chunk::Surrogate(c) => Wtf8Buf::from(c),
})
.collect::<Wtf8Buf>()
.into(),
PyKindStr::Ascii(s) => s.to_ascii_lowercase().into(),
PyKindStr::Utf8(s) => CaseMapper::new().fold_string(s).to_string().into(),
PyKindStr::Wtf8(w) => {
let mut out = VecFmtWriter(Vec::with_capacity(w.len()));
let mapper = CaseMapper::new();
for chunk in w.as_bytes().utf8_chunks() {
mapper
.fold(chunk.valid())
.write_to(&mut out)
.expect("Writing to an in-memory buffer cannot fail.");
out.0.extend(chunk.invalid());
}
// SAFETY:
// * CaseMapper only produces valid UTF-8
// * Surrogates are appended as-is
unsafe { Wtf8Buf::from_bytes_unchecked(out.0) }.into()
}
}
}

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