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GeezerVison is showing github.com — Fix swapcase() by joshuamegnauth54 · Pull Request #7788 · RustPython/RustPython

Fix swapcase() #7788

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Merged

youknowone merged 1 commit into RustPython:main from joshuamegnauth54:swapcase-fixes

May 13, 2026

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Merged

Fix swapcase() #7788

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joshuamegnauth54 May 5, 2026

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1 change: 0 additions & 1 deletion 1 Lib/test/test_str.py

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -972,7 +972,6 @@ def test_title(self):
		self.assertEqual('A\u03a3 \u1fa1xy'.title(), 'A\u03c2 \u1fa9xy')
		self.assertEqual('A\u03a3A'.title(), 'A\u03c3a')

		@unittest.expectedFailure # TODO: RUSTPYTHON; + 𐐧
		def test_swapcase(self):
		string_tests.StringLikeTest.test_swapcase(self)
		self.assertEqual('\U0001044F'.swapcase(), '\U00010427')
Expand Down

59 changes: 45 additions & 14 deletions 59 crates/vm/src/builtins/str.rs

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -11,10 +11,13 @@ use crate::{
		TryFromBorrowedObject, VirtualMachine,
		anystr::{self, AnyStr, AnyStrContainer, AnyStrWrapper, adjust_indices},
		atomic_func,
		bytes_inner::{swapcase_ascii, title_ascii},
		cformat::cformat_string,
		class::PyClassImpl,
		common::lock::LazyLock,
		common::str::{PyKindStr, StrData, StrKind},
		common::{
		lock::LazyLock,
		str::{PyKindStr, StrData, StrKind},
		},
		convert::{IntoPyException, ToPyException, ToPyObject, ToPyResult},
		format::{format, format_map},
		function::{ArgIterable, ArgSize, FuncArgs, OptionalArg, OptionalOption, PyComparisonValue},
Expand Down Expand Up		@@ -1078,7 +1081,7 @@ impl PyStr {
		fn title(&self) -> Wtf8Buf {
		match self.as_str_kind() {
		PyKindStr::Ascii(_) => unsafe {
		Wtf8Buf::from_bytes_unchecked(crate::bytes_inner::title_ascii(self.as_bytes()))
		Wtf8Buf::from_bytes_unchecked(title_ascii(self.as_bytes()))
		},
		PyKindStr::Utf8(s) => {
		let mut out = VecFmtWriter(Vec::with_capacity(s.len()));
Expand All		@@ -1102,19 +1105,29 @@ impl PyStr {

		#[pymethod]
		fn swapcase(&self) -> Wtf8Buf {
		let mut swapped_str = Wtf8Buf::with_capacity(self.data.len());
		for c_orig in self.as_wtf8().code_points() {
		let c = c_orig.to_char_lossy();
		// to_uppercase returns an iterator because case changes may be multiple bytes
		if c.is_lowercase() {
		swapped_str.extend(c.to_uppercase());
		} else if c.is_uppercase() {
		swapped_str.extend(c.to_lowercase());
		} else {
		swapped_str.push(c_orig);
		match self.as_str_kind() {
		PyKindStr::Ascii(s) => unsafe {
		// SAFETY: ASCII is valid Unicode and swapcase_ascii does not produce non-ASCII.
		Wtf8Buf::from_bytes_unchecked(swapcase_ascii(s.as_bytes()))
		},
		PyKindStr::Utf8(s) => {
		let mut out = VecFmtWriter(Vec::with_capacity(s.len()));
		swapcase_utf8(s, &mut out);
		// SAFETY: `s` is valid UTF-8 and swapcase_utf8 only works on Unicode.
		unsafe { Wtf8Buf::from_bytes_unchecked(out.0) }
		}
		PyKindStr::Wtf8(s) => {
		let mut out = VecFmtWriter(Vec::with_capacity(s.len()));
		for chunk in s.as_bytes().utf8_chunks() {
		swapcase_utf8(chunk.valid(), &mut out);
		out.0.extend(chunk.invalid());
		}
		// SAFETY:
		// * `s` is valid WTF-8; surrogate bytes were appended without processing.
		// * swapcase_utf8 produces valid UTF-8.
		unsafe { Wtf8Buf::from_bytes_unchecked(out.0) }
		}
		}
		swapped_str
		}

		#[pymethod]
Expand Down Expand Up		@@ -1648,6 +1661,24 @@ fn handle_capital_sigma(s: &str, i: usize) -> char {
		if before && !after { 'ς' } else { 'σ' }
		}

		fn swapcase_utf8(s: &str, out: &mut VecFmtWriter) {
		for (i, ch) in s.char_indices() {
		if ch.is_uppercase() {
		lowercase_or_sigma(ch, s, i, out);
		} else if ch.is_lowercase() {
		for ch in ch.to_uppercase() {
		let mut buf = [0u8; 4];
		let s = ch.encode_utf8(&mut buf);
		out.0.extend(s.as_bytes());
		}
		} else {
		let mut buf = [0u8; 4];
		let s = ch.encode_utf8(&mut buf);
		out.0.extend(s.as_bytes());
		}
		}
		}
Comment thread coderabbitai[bot] marked this conversation as resolved. Resolved Uh oh! There was an error while loading. Please reload this page.

		impl PyRef<PyStr> {
		#[must_use]
		pub fn is_empty(&self) -> bool {
Expand Down

17 changes: 8 additions & 9 deletions 17 crates/vm/src/bytes_inner.rs

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -413,15 +413,7 @@ impl PyBytesInner {
		}

		pub fn swapcase(&self) -> Vec<u8> {
		let mut new: Vec<u8> = Vec::with_capacity(self.elements.len());
		for w in &self.elements {
		match w {
		b'A'..=b'Z' => new.push(w.to_ascii_lowercase()),
		b'a'..=b'z' => new.push(w.to_ascii_uppercase()),
		x => new.push(*x),
		}
		}
		new
		swapcase_ascii(self.as_bytes())
		}

		pub fn hex(
Expand Down Expand Up		@@ -1238,3 +1230,10 @@ pub(crate) fn title_ascii(bytes: &[u8]) -> Vec<u8> {
		}
		out
		}

		pub(crate) fn swapcase_ascii(bytes: &[u8]) -> Vec<u8> {
		bytes
		.iter()
		.map(\|&b\| if b.is_ascii_alphabetic() { b ^ 0x20 } else { b })
		.collect()
		}

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