test: Add tests for user language detection and normalization

aider/coders/base_coder.py

@@ -1103,7 +1103,7 @@ class Coder:
             if lang:
                 return self.normalize_language(lang)
         except Exception:
-            pass  # pragma: no cover
+            pass
 
         # Environment variables
         for env_var in ("LANG", "LANGUAGE", "LC_ALL", "LC_MESSAGES"):

tests/basic/test_coder.py

@@ -1,5 +1,6 @@
 import os
 import tempfile
+import locale
 import unittest
 from pathlib import Path
 from unittest.mock import MagicMock, patch
@@ -1181,6 +1182,112 @@ This command will print 'Hello, World!' to the console."""
             sanity_check_messages(coder.cur_messages)
             self.assertEqual(coder.cur_messages[-1]["role"], "assistant")
 
+    def test_normalize_language(self):
+        coder = Coder.create(self.GPT35, None, io=InputOutput())
+
+        # Test None and empty
+        self.assertIsNone(coder.normalize_language(None))
+        self.assertIsNone(coder.normalize_language(""))
+
+        # Test "C" and "POSIX"
+        self.assertIsNone(coder.normalize_language("C"))
+        self.assertIsNone(coder.normalize_language("POSIX"))
+
+        # Test already formatted names
+        self.assertEqual(coder.normalize_language("English"), "English")
+        self.assertEqual(coder.normalize_language("French"), "French")
+
+        # Test common locale codes (fallback map, assuming babel is not installed or fails)
+        with patch("aider.coders.base_coder.Locale", None):
+            self.assertEqual(coder.normalize_language("en_US"), "English")
+            self.assertEqual(coder.normalize_language("fr_FR"), "French")
+            self.assertEqual(coder.normalize_language("es"), "Spanish")
+            self.assertEqual(coder.normalize_language("de_DE.UTF-8"), "German")
+            self.assertEqual(coder.normalize_language("ja"), "Japanese")
+            self.assertEqual(coder.normalize_language("unknown_code"), "unknown_code") # Fallback to original
+
+        # Test with babel.Locale mocked (available)
+        mock_babel_locale = MagicMock()
+        mock_locale_instance = MagicMock()
+        mock_locale_instance.get_display_name.return_value = "english" # babel returns lowercase
+        mock_babel_locale.parse.return_value = mock_locale_instance
+
+        with patch("aider.coders.base_coder.Locale", mock_babel_locale):
+            self.assertEqual(coder.normalize_language("en_US"), "English")
+            mock_babel_locale.parse.assert_called_with("en_US")
+            mock_locale_instance.get_display_name.assert_called_with("en")
+
+            self.assertEqual(coder.normalize_language("fr-FR"), "French") # Test with hyphen
+            mock_babel_locale.parse.assert_called_with("fr_FR") # Hyphen replaced
+
+        # Test with babel.Locale raising an exception (simulating parse failure)
+        mock_babel_locale_error = MagicMock()
+        mock_babel_locale_error.parse.side_effect = Exception("Babel parse error")
+        with patch("aider.coders.base_coder.Locale", mock_babel_locale_error):
+            self.assertEqual(coder.normalize_language("en_US"), "English") # Falls back to map
+
+    def test_get_user_language(self):
+        io = InputOutput()
+        coder = Coder.create(self.GPT35, None, io=io)
+
+        # 1. Test with self.chat_language set
+        coder.chat_language = "fr_CA"
+        with patch.object(coder, "normalize_language", return_value="French Canadian") as mock_norm:
+            self.assertEqual(coder.get_user_language(), "French Canadian")
+            mock_norm.assert_called_once_with("fr_CA")
+        coder.chat_language = None # Reset
+
+        # 2. Test with locale.getlocale()
+        with patch("locale.getlocale", return_value=("en_GB", "UTF-8")) as mock_getlocale:
+            with patch.object(coder, "normalize_language", return_value="British English") as mock_norm:
+                self.assertEqual(coder.get_user_language(), "British English")
+                mock_getlocale.assert_called_once()
+                mock_norm.assert_called_once_with("en_GB")
+
+        # Test with locale.getlocale() returning None or empty
+        with patch("locale.getlocale", return_value=(None, None)) as mock_getlocale:
+            with patch("os.environ.get") as mock_env_get: # Ensure env vars are not used yet
+                mock_env_get.return_value = None
+                self.assertIsNone(coder.get_user_language()) # Should be None if nothing found
+
+        # 3. Test with environment variables
+        env_vars_to_test = ["LANG", "LANGUAGE", "LC_ALL", "LC_MESSAGES"]
+
+        # Test LANG
+        with patch("locale.getlocale", side_effect=Exception("locale error")): # Mock locale to fail
+            with patch("os.environ.get") as mock_env_get:
+                mock_env_get.side_effect = lambda key: "de_DE.UTF-8" if key == "LANG" else None
+                with patch.object(coder, "normalize_language", return_value="German") as mock_norm:
+                    self.assertEqual(coder.get_user_language(), "German")
+                    mock_env_get.assert_any_call("LANG")
+                    mock_norm.assert_called_once_with("de_DE")
+
+        # Test LANGUAGE (takes precedence over LANG if both were hypothetically checked by os.environ.get)
+        # but our code checks in order, so we only need to mock the first one it finds.
+        with patch("locale.getlocale", side_effect=Exception("locale error")):
+            with patch("os.environ.get") as mock_env_get:
+                mock_env_get.side_effect = lambda key: "es_ES" if key == "LANGUAGE" else None
+                with patch.object(coder, "normalize_language", return_value="Spanish") as mock_norm:
+                    self.assertEqual(coder.get_user_language(), "Spanish")
+                    mock_env_get.assert_any_call("LANGUAGE") # LANG would be called first
+                    mock_norm.assert_called_once_with("es_ES")
+
+        # 4. Test priority: chat_language > locale > env
+        coder.chat_language = "it_IT"
+        with patch("locale.getlocale", return_value=("en_US", "UTF-8")) as mock_getlocale:
+            with patch("os.environ.get", return_value="de_DE") as mock_env_get:
+                with patch.object(coder, "normalize_language", side_effect=lambda x: x.upper()) as mock_norm:
+                    self.assertEqual(coder.get_user_language(), "IT_IT") # From chat_language
+                    mock_norm.assert_called_once_with("it_IT")
+                    mock_getlocale.assert_not_called()
+                    mock_env_get.assert_not_called()
+        coder.chat_language = None
+
+        # 5. Test when no language is found
+        with patch("locale.getlocale", side_effect=Exception("locale error")):
+            with patch("os.environ.get", return_value=None) as mock_env_get:
+                self.assertIsNone(coder.get_user_language())
+
     def test_architect_coder_auto_accept_true(self):
         with GitTemporaryDirectory():
             io = InputOutput(yes=True)