fix(wc): keep WASI default locale UTF-8 compatible

WASI does not provide an ambient locale, so treating a missing LC_CTYPE/LANG as C/POSIX makes wc -m count bytes by default. Preserve the existing UTF-8 behavior for WASI while keeping POSIX fallback on platforms with native locale environments.

Author: naoNao89

src/uucore/src/lib/features/i18n/charmap.rs

@@ -41,11 +41,24 @@ fn get_effective_ctype_locale() -> Option<String> {
 
 /// Return whether the effective `LC_CTYPE` locale is the byte-oriented C/POSIX locale.
 ///
-/// A missing effective locale defaults to POSIX behavior. Only exact `C` and
-/// `POSIX` locale values are treated as explicit C/POSIX locales; locales such
-/// as `C.UTF-8` are not.
+/// WASI has no native locale environment, so it keeps the existing
+/// UTF-8-compatible behavior regardless of forwarded locale variables.
+#[cfg(target_os = "wasi")]
 pub fn is_effective_ctype_c_or_posix() -> bool {
-    get_effective_ctype_locale().is_none_or(|locale| locale == "C" || locale == "POSIX")
+    false
+}
+
+/// Return whether the effective `LC_CTYPE` locale is the byte-oriented C/POSIX locale.
+///
+/// A missing effective locale defaults to POSIX behavior on platforms with a
+/// native locale environment.
+#[cfg(not(target_os = "wasi"))]
+pub fn is_effective_ctype_c_or_posix() -> bool {
+    match get_effective_ctype_locale().as_deref() {
+        Some("C" | "POSIX") => true,
+        Some(_) => false,
+        None => true,
+    }
 }
 
 fn get_encoding() -> &'static MbEncoding {

tests/by-util/test_wc.rs

@@ -983,6 +983,7 @@ fn test_posixly_correct_whitespace() {
 }
 
 #[test]
+#[cfg_attr(wasi_runner, ignore = "WASI has no native C/POSIX locale")]
 fn test_wc_chars_c_locale() {
     // In C/POSIX locale, wc -m should count bytes, not UTF-8 characters
     // Vietnamese "Tiếng Việt" uses diacritics (2 bytes per char in UTF-8)
@@ -1057,6 +1058,7 @@ fn test_wc_chars_utf8_locale() {
 }
 
 #[test]
+#[cfg_attr(wasi_runner, ignore = "WASI has no native C/POSIX locale")]
 fn test_wc_chars_default_locale() {
     // When no locale is set (empty LC_ALL), it defaults to POSIX (chars == bytes)
     // This ensures backward compatibility
@@ -1084,6 +1086,7 @@ fn test_wc_chars_default_locale() {
 }
 
 #[test]
+#[cfg_attr(wasi_runner, ignore = "WASI has no native C/POSIX locale")]
 fn test_wc_multibyte_c_locale() {
     // Issue #9712 and #5831: Test various multibyte characters in C locale
     // All should be counted as bytes