fix(ls): use GetACP to detect UTF-8 encoding on Windows

On Windows, locale environment variables (LC_ALL, LC_COLLATE, LANG)
are typically unset, causing get_locale_from_env() to default to
UEncoding::Ascii. This makes non-ASCII filenames display as octal
escape sequences or `?` characters in ls output.

Fix by querying the system ANSI code page via GetACP() when no locale
variables are set. If the active code page is 65001 (UTF-8), use
UEncoding::Utf8. This aligns with GNU coreutils' gnulib approach
which calls locale_charset() -> GetACP() on Windows.

Fixes: #11103

Author: mattsu2020

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

@@ -28,6 +28,24 @@ pub enum UEncoding {
 // This ensures real locales like "en-US" won't match
 const DEFAULT_LOCALE: Locale = locale!("und");
 
+/// On Windows, detect the encoding from the system ANSI code page.
+/// Returns `UEncoding::Utf8` if the active code page is 65001 (UTF-8),
+/// otherwise `UEncoding::Ascii`.
+///
+/// This mirrors the GNU lib approach where `locale_charset()` calls `GetACP()` on Windows.
+#[cfg(target_os = "windows")]
+fn get_windows_encoding() -> UEncoding {
+    unsafe extern "system" {
+        fn GetACP() -> u32;
+    }
+    let acp = unsafe { GetACP() };
+    if acp == 65001 {
+        UEncoding::Utf8
+    } else {
+        UEncoding::Ascii
+    }
+}
+
 /// Look at 3 environment variables in the following order
 ///
 /// 1. LC_ALL
@@ -70,8 +88,18 @@ pub fn get_locale_from_env(locale_name: &str) -> (Locale, UEncoding) {
             return (locale, encoding);
         }
     }
-    // Default POSIX locale representing LC_ALL=C
-    (DEFAULT_LOCALE, UEncoding::Ascii)
+    // No locale environment variables set.
+    // On Windows, check the system ANSI code page to determine encoding,
+    // matching GNU coreutils' approach (locale_charset -> GetACP).
+    #[cfg(target_os = "windows")]
+    {
+        (DEFAULT_LOCALE, get_windows_encoding())
+    }
+    #[cfg(not(target_os = "windows"))]
+    {
+        // Default POSIX locale representing LC_ALL=C
+        (DEFAULT_LOCALE, UEncoding::Ascii)
+    }
 }
 
 /// Get the collating locale from the environment

tests/by-util/test_ls.rs

@@ -7195,3 +7195,81 @@ fn test_ls_a_dotdot_no_error_on_wasi() {
         .stdout_contains("..")
         .no_stderr();
 }
+
+/// Verify that ls correctly detects encoding from locale environment variables.
+/// Non-ASCII filenames should be escaped in C/POSIX/non-UTF-8 locales
+/// and displayed as-is in UTF-8 locales.
+#[cfg(not(any(target_vendor = "apple", target_os = "windows", target_os = "openbsd")))]
+mod locale_encoding {
+    use uutests::util::TestScenario;
+    use uutests::util_name;
+
+    /// Create a file with a non-ASCII name and check ls output with the given locale.
+    /// If `expect_utf8` is true, assert the filename is shown as-is (UTF-8 locale).
+    /// Otherwise, assert the non-ASCII character is escaped (ASCII locale).
+    fn check_locale(locale: &str, expect_utf8: bool) {
+        let scene = TestScenario::new(util_name!());
+        let at = &scene.fixtures;
+        let filename = uucore::os_str_from_bytes("é".as_bytes())
+            .expect("should be valid Unicode");
+        at.touch(filename);
+
+        let result = scene
+            .ucmd()
+            .env("LC_ALL", locale)
+            .arg("--quoting-style=shell-escape")
+            .succeeds();
+
+        if expect_utf8 {
+            result.stdout_contains("é");
+        } else {
+            result.stdout_does_not_contain("é");
+        }
+    }
+
+    #[test]
+    fn test_ls_locale_c_escapes_non_ascii() {
+        check_locale("C", false);
+    }
+
+    #[test]
+    fn test_ls_locale_posix_escapes_non_ascii() {
+        check_locale("POSIX", false);
+    }
+
+    #[test]
+    fn test_ls_locale_utf8_suffix_shows_non_ascii() {
+        check_locale("en_US.UTF-8", true);
+    }
+
+    #[test]
+    fn test_ls_locale_utf8_lowercase_shows_non_ascii() {
+        check_locale("en_US.utf8", true);
+    }
+
+    #[test]
+    fn test_ls_locale_iso8859_escapes_non_ascii() {
+        check_locale("en_US.ISO-8859-1", false);
+    }
+
+    #[test]
+    fn test_ls_locale_no_encoding_suffix_escapes_non_ascii() {
+        check_locale("en_US", false);
+    }
+}
+
+/// On Windows, verify that ls can display non-ASCII filenames correctly
+/// when the system ANSI code page is set to UTF-8 (ACP 65001).
+#[cfg(target_os = "windows")]
+#[test]
+fn test_ls_windows_non_ascii_filename() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.touch("文件1");
+
+    scene
+        .ucmd()
+        .succeeds()
+        .stdout_contains("文件1")
+        .no_stderr();
+}