gh-124969: Fix locale.nl_langinfo(locale.ALT_DIGITS) (GH-124974)

Now it returns a tuple of up to 100 strings (an empty tuple on most locales).
Previously it returned the first item of that tuple or an empty string.

Author: serhiy-storchaka

Doc/library/locale.rst

@@ -158,7 +158,8 @@ The :mod:`locale` module defines the following exception and functions:
 
 .. function:: nl_langinfo(option)
 
-   Return some locale-specific information as a string.  This function is not
+   Return some locale-specific information as a string (or a tuple for
+   ``ALT_DIGITS``).  This function is not
    available on all systems, and the set of possible options might also vary
    across platforms.  The possible argument values are numbers, for which
    symbolic constants are available in the locale module.
@@ -311,8 +312,7 @@ The :mod:`locale` module defines the following exception and functions:
 
    .. data:: ALT_DIGITS
 
-      Get a representation of up to 100 values used to represent the values
-      0 to 99.
+      Get a tuple of up to 100 strings used to represent the values 0 to 99.
 
    The function temporarily sets the ``LC_CTYPE`` locale to the locale
    of the category that determines the requested value (``LC_TIME``,

Lib/test/test__locale.py

@@ -1,4 +1,4 @@
-from _locale import (setlocale, LC_ALL, LC_CTYPE, LC_NUMERIC, localeconv, Error)
+from _locale import (setlocale, LC_ALL, LC_CTYPE, LC_NUMERIC, LC_TIME, localeconv, Error)
 try:
     from _locale import (RADIXCHAR, THOUSEP, nl_langinfo)
 except ImportError:
@@ -74,6 +74,17 @@ def accept(loc):
     'ps_AF': ('\u066b', '\u066c'),
 }
 
+known_alt_digits = {
+    'C': (0, {}),
+    'en_US': (0, {}),
+    'fa_IR': (100, {0: '\u06f0\u06f0', 10: '\u06f1\u06f0', 99: '\u06f9\u06f9'}),
+    'ja_JP': (100, {0: '\u3007', 10: '\u5341', 99: '\u4e5d\u5341\u4e5d'}),
+    'lzh_TW': (32, {0: '\u3007', 10: '\u5341', 31: '\u5345\u4e00'}),
+    'my_MM': (100, {0: '\u1040\u1040', 10: '\u1041\u1040', 99: '\u1049\u1049'}),
+    'or_IN': (100, {0: '\u0b66', 10: '\u0b67\u0b66', 99: '\u0b6f\u0b6f'}),
+    'shn_MM': (100, {0: '\u1090\u1090', 10: '\u1091\u1090', 99: '\u1099\u1099'}),
+}
+
 if sys.platform == 'win32':
     # ps_AF doesn't work on Windows: see bpo-38324 (msg361830)
     del known_numerics['ps_AF']
@@ -179,6 +190,34 @@ def test_lc_numeric_basic(self):
         if not tested:
             self.skipTest('no suitable locales')
 
+    @unittest.skipUnless(nl_langinfo, "nl_langinfo is not available")
+    @unittest.skipUnless(hasattr(locale, 'ALT_DIGITS'), "requires locale.ALT_DIGITS")
+    @unittest.skipIf(
+        support.is_emscripten or support.is_wasi,
+        "musl libc issue on Emscripten, bpo-46390"
+    )
+    def test_alt_digits_nl_langinfo(self):
+        # Test nl_langinfo(ALT_DIGITS)
+        tested = False
+        for loc, (count, samples) in known_alt_digits.items():
+            with self.subTest(locale=loc):
+                try:
+                    setlocale(LC_TIME, loc)
+                except Error:
+                    self.skipTest(f'no locale {loc!r}')
+                    continue
+                with self.subTest(locale=loc):
+                    alt_digits = nl_langinfo(locale.ALT_DIGITS)
+                    self.assertIsInstance(alt_digits, tuple)
+                    if count and not alt_digits and sys.platform == 'darwin':
+                        self.skipTest(f'ALT_DIGITS is not set for locale {loc!r} on macOS')
+                    self.assertEqual(len(alt_digits), count)
+                    for i in samples:
+                        self.assertEqual(alt_digits[i], samples[i])
+                    tested = True
+        if not tested:
+            self.skipTest('no suitable locales')
+
     def test_float_parsing(self):
         # Bug #1391872: Test whether float parsing is okay on European
         # locales.

Misc/NEWS.d/next/Library/2024-10-08-12-09-09.gh-issue-124969._VBQLq.rst

@@ -0,0 +1,3 @@
+Fix ``locale.nl_langinfo(locale.ALT_DIGITS)``. Now it returns a tuple of up
+to 100 strings (an empty tuple on most locales). Previously it returned the
+first item of that tuple or an empty string.

Modules/_localemodule.c

@@ -666,9 +666,35 @@ _locale_nl_langinfo_impl(PyObject *module, int item)
             {
                 return NULL;
             }
-            PyObject *unicode = PyUnicode_DecodeLocale(result, NULL);
+            PyObject *pyresult;
+#ifdef ALT_DIGITS
+            if (item == ALT_DIGITS) {
+                /* The result is a sequence of up to 100 NUL-separated strings. */
+                const char *s = result;
+                int count = 0;
+                for (; count < 100 && *s; count++) {
+                    s += strlen(s) + 1;
+                }
+                pyresult = PyTuple_New(count);
+                if (pyresult != NULL) {
+                    for (int i = 0; i < count; i++) {
+                        PyObject *unicode = PyUnicode_DecodeLocale(result, NULL);
+                        if (unicode == NULL) {
+                            Py_CLEAR(pyresult);
+                            break;
+                        }
+                        PyTuple_SET_ITEM(pyresult, i, unicode);
+                        result += strlen(result) + 1;
+                    }
+                }
+            }
+            else
+#endif
+            {
+                pyresult = PyUnicode_DecodeLocale(result, NULL);
+            }
             restore_locale(oldloc);
-            return unicode;
+            return pyresult;
         }
     }
     PyErr_SetString(PyExc_ValueError, "unsupported langinfo constant");