Cache validity of a locale name

Currently `_cache` is only populated on `load`, this is an issue with
code which do a lot of locale parsing / instantiation but for one
reason or an other rarely end up needing to actually load the locale
data (e.g. date formatting with non-locale-dependent patterns) because
every cache miss is an `os.path.exists`.

Cache `exists` separately.

Update test because `lru_cache` requires all parameters to be
hashasble and a list is not that.

Author: xmo-odoo

babel/localedata.py

@@ -60,6 +60,7 @@ def resolve_locale_filename(name: os.PathLike[str] | str) -> str:
     return os.path.join(_dirname, f"{name}.dat")
 
 
+@lru_cache(maxsize=None)
 def exists(name: str) -> bool:
     """Check whether locale data is available for the given locale.
 
@@ -72,7 +73,7 @@ def exists(name: str) -> bool:
     if name in _cache:
         return True
     file_found = os.path.exists(resolve_locale_filename(name))
-    return True if file_found else bool(normalize_locale(name))
+    return file_found or bool(normalize_locale(name))
 
 
 @lru_cache(maxsize=None)

tests/test_localedata.py

@@ -109,10 +109,10 @@ def test_locale_argument_acceptance():
     assert normalized_locale is None
     assert not localedata.exists(None)
 
-    # Testing list input.
+    # Testing tuple input.
     normalized_locale = localedata.normalize_locale(['en_us', None])
     assert normalized_locale is None
-    assert not localedata.exists(['en_us', None])
+    assert not localedata.exists(('en_us', None))
 
 
 def test_locale_identifiers_cache(monkeypatch):