gh-64243: Implement locale.getlocale fall back in gettext.find

Doc/library/gettext.rst

@@ -131,7 +131,7 @@ install themselves in the built-in namespace as the function :func:`!_`.
 
    If *localedir* is not given, then the default system locale directory is used.
    [#]_  If *languages* is not given, then the environment variable :envvar:`LANGUAGE`
-   is searched, it falls back to :func:`locale.getlocale`, which in turn falls
+   is searched, it falls back to :func:`locale.setlocale`, which in turn falls
    back to the environment variables :envvar:`LC_ALL`, :envvar:`LC_MESSAGES`, and
    :envvar:`LANG` where the first one returning a non-empty value is used for the
    *languages* variable. The environment variables should contain a colon separated
@@ -149,7 +149,7 @@ install themselves in the built-in namespace as the function :func:`!_`.
    the environment variables.
 
    .. versionchanged:: next
-      :func:`locale.getlocale` is used to generate *languages* if *languages* is
+      :func:`locale.setlocale` is used to generate *languages* if *languages* is
       not provided.
 
 .. function:: translation(domain, localedir=None, languages=None, class_=None, fallback=False)

Lib/gettext.py

@@ -230,7 +230,6 @@ def func(n):
 
 
 def _expand_lang(loc):
-    import locale
     loc = locale.normalize(loc)
     COMPONENT_CODESET   = 1 << 0
     COMPONENT_TERRITORY = 1 << 1
@@ -494,7 +493,7 @@ def find(domain, localedir=None, languages=None, all=False):
         languages = []
         if val := os.environ.get('LANGUAGE'):
             languages = val.split(':')
-        elif (loc := locale.getlocale()) != (None, None):
+        elif (loc := locale.setlocale(locale.LC_MESSAGES)) != (None, None):
             languages = [".".join(filter(None, loc))]
         else:
             for envar in ('LC_ALL', 'LC_MESSAGES', 'LANG'):

Lib/test/test_gettext.py

@@ -1,4 +1,3 @@
-import locale
 import os
 import base64
 import gettext
@@ -737,30 +736,32 @@ def create_mo_file(self, lang):
             f.write(GNU_MO_DATA)
         return mo_file
 
-    @unittest.mock.patch("locale.getlocale", return_value=(None, None))
-    def test_find_with_env_vars(self, patch_getlocale):
-        # test that find correctly finds the environment variables
-        # when languages are not supplied
-        mo_file = self.create_mo_file("ga_IE")
-        for var in ('LANGUAGE', 'LC_ALL', 'LC_MESSAGES', 'LANG'):
-            self.env.set(var, 'ga_IE')
-            result = gettext.find("mofile",
-                                  localedir=os.path.join(self.tempdir, "locale"))
-            self.assertEqual(result, mo_file)
-            self.env.unset(var)
-        # test fallbacks
+    def _for_all_vars(self, mo_file, locale):
         for var in ('LANGUAGE', 'LC_ALL', 'LC_MESSAGES', 'LANG'):
-            self.env.set(var, 'es_ES:ga_IE:fr_FR')
+            self.env.set(var, locale)
             result = gettext.find("mofile",
                                   localedir=os.path.join(self.tempdir, "locale"))
-            self.assertEqual(result, mo_file)
+            self.assertEqual(mo_file, result)
             self.env.unset(var)
 
-    @unittest.mock.patch("locale.getlocale", return_value=('ga_IE', 'UTF-8'))
-    def test_process_vars_override(self, patch_getlocale):
+    @unittest.mock.patch("locale.setlocale", return_value=(None, None))
+    def test_find_with_env_vars(self, patch_getlocale):
+        # test that find correctly finds the environment variables
+        # when languages are not supplied
         mo_file = self.create_mo_file("ga_IE")
-        result = gettext.find("mofile", localedir=os.path.join(self.tempdir, "locale"))
-        self.assertEqual(result, mo_file)
+        self._for_all_vars(mo_file, "ga_IE")
+        self._for_all_vars(mo_file, "ga_IE.UTF-8")
+        self._for_all_vars(mo_file, "es_ES:ga_IE:fr_FR")
+        self._for_all_vars(mo_file, "ga_IE@euro")
+
+    def test_process_vars_override(self):
+        mo_file = self.create_mo_file("ga_IE")
+        with unittest.mock.patch("locale.setlocale", return_value=('ga_IE', 'UTF-8')):
+            result = gettext.find("mofile", localedir=os.path.join(self.tempdir, "locale"))
+            self.assertEqual(mo_file, result)
+        with unittest.mock.patch("locale.setlocale", return_value=('ga_IE', None)):
+            result = gettext.find("mofile", localedir=os.path.join(self.tempdir, "locale"))
+            self.assertEqual(mo_file, result)
 
     def test_find_with_languages(self):
         # test that passed languages are used