Add get_values_for_keys function to utils (#607)

* Add get_values_for_keys function to utils
* Error text improvement and formatting

constance/utils.py

@@ -20,3 +20,26 @@ def get_values():
     default_initial = ((name, options[0]) for name, options in settings.CONFIG.items())
     # Then update the mapping with actually values from the backend
     return dict(default_initial, **dict(config._backend.mget(settings.CONFIG)))
+
+
+def get_values_for_keys(keys):
+    """
+    Retrieve values for specified keys from the backend.
+
+    :param keys: List of keys to retrieve.
+    :return: Dictionary with values for the specified keys.
+    :raises AttributeError: If any key is not found in the configuration.
+    """
+    if not isinstance(keys, (list, tuple, set)):
+        raise TypeError('keys must be a list, tuple, or set of strings')
+
+    # Prepare default initial mapping
+    default_initial = {name: options[0] for name, options in settings.CONFIG.items() if name in keys}
+
+    # Check if all keys are present in the default_initial mapping
+    missing_keys = [key for key in keys if key not in default_initial]
+    if missing_keys:
+        raise AttributeError(f'"{", ".join(missing_keys)}" keys not found in configuration.')
+
+    # Merge default values and backend values, prioritizing backend values
+    return dict(default_initial, **dict(config._backend.mget(keys)))

tests/test_utils.py

@@ -5,7 +5,7 @@
 from django.test import TestCase
 
 from constance.management.commands.constance import _set_constance_value
-from constance.utils import get_values
+from constance.utils import get_values, get_values_for_keys
 
 
 class UtilsTestCase(TestCase):
@@ -62,3 +62,29 @@ def test_get_values(self):
                 },
             },
         )
+
+    def test_get_values_for_keys(self):
+        self.assertEqual(
+            get_values_for_keys(['BOOL_VALUE', 'CHOICE_VALUE', 'LINEBREAK_VALUE']),
+            {
+                'BOOL_VALUE': True,
+                'CHOICE_VALUE': 'yes',
+                'LINEBREAK_VALUE': 'Spam spam',
+            },
+        )
+
+    def test_get_values_for_keys_empty_keys(self):
+        result = get_values_for_keys([])
+        self.assertEqual(result, {})
+
+    def test_get_values_for_keys_throw_error_if_no_key(self):
+        self.assertRaisesMessage(
+            AttributeError,
+            '"OLD_VALUE, BOLD_VALUE" keys not found in configuration.',
+            get_values_for_keys,
+            ['BOOL_VALUE', 'OLD_VALUE', 'BOLD_VALUE'],
+        )
+
+    def test_get_values_for_keys_invalid_input_type(self):
+        with self.assertRaises(TypeError):
+            get_values_for_keys('key1')