solaar: clean up locale code

Usage example for German:
LC_ALL=de_DE.UTF-8 solaar

Related #2507

lib/solaar/gtk.py

@@ -19,6 +19,7 @@
 import argparse
 import faulthandler
 import importlib
+import locale
 import logging
 import os.path
 import platform
@@ -31,7 +32,6 @@ from traceback import format_exc
 import solaar.cli as _cli
 import solaar.configuration as _configuration
 import solaar.dbus as _dbus
-import solaar.i18n as _i18n
 import solaar.listener as _listener
 import solaar.ui as _ui
 import solaar.ui.common as _common
@@ -122,7 +122,8 @@ def _parse_arguments():
 
     if not args.action:
         if logger.isEnabledFor(logging.INFO):
-            logger.info("version %s, language %s (%s)", __version__, _i18n.language, _i18n.encoding)
+            language, encoding = locale.getlocale()
+            logger.info("version %s, language %s (%s)", __version__, language, encoding)
 
     return args
 

lib/solaar/i18n.py

@@ -14,43 +14,52 @@
 ## with this program; if not, write to the Free Software Foundation, Inc.,
 ## 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
-import gettext as _gettext
+import gettext
 import locale
-import os.path as _path
-import sys as _sys
+import os
+import sys
 
-from glob import glob as _glob
+from glob import glob
 
-from solaar import NAME as _NAME
+from solaar import NAME
 
-#
-#
-#
+_LOCALE_DOMAIN = NAME.lower()
 
 
-def _find_locale_path(lc_domain):
-    prefix_share = _path.normpath(_path.join(_path.realpath(_sys.path[0]), ".."))
-    src_share = _path.normpath(_path.join(_path.realpath(_sys.path[0]), "..", "share"))
+def _find_locale_path(locale_domain: str) -> str:
+    prefix_share = os.path.normpath(os.path.join(os.path.realpath(sys.path[0]), ".."))
+    src_share = os.path.normpath(os.path.join(os.path.realpath(sys.path[0]), "..", "share"))
 
     for location in prefix_share, src_share:
-        mo_files = _glob(_path.join(location, "locale", "*", "LC_MESSAGES", lc_domain + ".mo"))
+        mo_files = glob(os.path.join(location, "locale", "*", "LC_MESSAGES", locale_domain + ".mo"))
         if mo_files:
-            return _path.join(location, "locale")
+            return os.path.join(location, "locale")
+    raise FileNotFoundError(f"Could not find locale path for {locale_domain}")
 
 
-try:
-    locale.setlocale(locale.LC_ALL, "")
-except Exception:
-    pass
+def set_locale_to_system_default():
+    """Sets locale for translations to the system default.
 
-language, encoding = locale.getlocale()
+    Set LC_ALL environment variable to enforce a locale setting e.g.
+    'de_DE.UTF-8'. Run Solaar with your desired localization, for German
+    use:
+    'LC_ALL=de_DE.UTF-8 solaar'
+    """
+    try:
+        locale.setlocale(locale.LC_ALL, "")
+    except PermissionError:
+        pass
 
-_LOCALE_DOMAIN = _NAME.lower()
-path = _find_locale_path(_LOCALE_DOMAIN)
+    try:
+        path = _find_locale_path(_LOCALE_DOMAIN)
+    except FileNotFoundError:
+        path = None
+    gettext.bindtextdomain(_LOCALE_DOMAIN, path)
+    gettext.textdomain(_LOCALE_DOMAIN)
+    gettext.install(_LOCALE_DOMAIN)
 
-_gettext.bindtextdomain(_LOCALE_DOMAIN, path)
-_gettext.textdomain(_LOCALE_DOMAIN)
-_gettext.install(_LOCALE_DOMAIN)
 
-_ = _gettext.gettext
-ngettext = _gettext.ngettext
+set_locale_to_system_default()
+
+_ = gettext.gettext
+ngettext = gettext.ngettext

tests/solaar/ui/test_i18n.py

@@ -0,0 +1,28 @@
+import locale
+import os
+import platform
+
+import pytest
+
+from solaar import i18n
+
+
+@pytest.fixture
+def set_locale_de():
+    backup_lang = os.environ.get("LC_ALL", "")
+    try:
+        yield
+    finally:
+        os.environ["LC_ALL"] = backup_lang
+        i18n.set_locale_to_system_default()
+
+
+@pytest.mark.skipif(platform.system() == "Linux", reason="Adapt test for Linux")
+def test_set_locale_to_system_default(set_locale_de):
+    os.environ["LC_ALL"] = "de_DE.UTF-8"
+    i18n.set_locale_to_system_default()
+
+    language, encoding = locale.getlocale()
+
+    assert language == "de_DE"
+    assert encoding == "UTF-8"