Use casefold to compare strings case insensitively (#184)

Author: haacked

posthog/feature_flags.py

@@ -7,6 +7,7 @@
 from dateutil import parser
 from dateutil.relativedelta import relativedelta
 
+from posthog import utils
 from posthog.utils import convert_to_datetime_aware, is_valid_regex
 
 __LONG_SCALE__ = float(0xFFFFFFFFFFFFFFF)
@@ -129,8 +130,8 @@ def match_property(property, property_values) -> bool:
 
         def compute_exact_match(value, override_value):
             if isinstance(value, list):
-                return str(override_value).lower() in [str(val).lower() for val in value]
-            return str(value).lower() == str(override_value).lower()
+                return str(override_value).casefold() in [str(val).casefold() for val in value]
+            return utils.str_iequals(value, override_value)
 
         if operator == "exact":
             return compute_exact_match(value, override_value)
@@ -141,10 +142,10 @@ def compute_exact_match(value, override_value):
         return key in property_values
 
     if operator == "icontains":
-        return str(value).lower() in str(override_value).lower()
+        return utils.str_icontains(override_value, value)
 
     if operator == "not_icontains":
-        return str(value).lower() not in str(override_value).lower()
+        return not utils.str_icontains(override_value, value)
 
     if operator == "regex":
         return is_valid_regex(str(value)) and re.compile(str(value)).search(str(override_value)) is not None

posthog/test/test_feature_flags.py

@@ -68,6 +68,59 @@ def test_flag_person_properties(self, patch_get):
         self.assertTrue(feature_flag_match)
         self.assertFalse(not_feature_flag_match)
 
+    def test_case_insensitive_matching(self):
+        self.client.feature_flags = [
+            {
+                "id": 1,
+                "name": "Beta Feature",
+                "key": "person-flag",
+                "is_simple_flag": True,
+                "active": True,
+                "filters": {
+                    "groups": [
+                        {
+                            "properties": [
+                                {
+                                    "key": "location",
+                                    "operator": "exact",
+                                    "value": ["Straße"],
+                                    "type": "person",
+                                }
+                            ],
+                            "rollout_percentage": 100,
+                        },
+                        {
+                            "properties": [
+                                {
+                                    "key": "star",
+                                    "operator": "exact",
+                                    "value": ["ſun"],
+                                    "type": "person",
+                                }
+                            ],
+                            "rollout_percentage": 100,
+                        },
+                    ],
+                },
+            }
+        ]
+
+        self.assertTrue(
+            self.client.get_feature_flag("person-flag", "some-distinct-id", person_properties={"location": "straße"})
+        )
+
+        self.assertTrue(
+            self.client.get_feature_flag("person-flag", "some-distinct-id", person_properties={"location": "strasse"})
+        )
+
+        self.assertTrue(
+            self.client.get_feature_flag("person-flag", "some-distinct-id", person_properties={"star": "ſun"})
+        )
+
+        self.assertTrue(
+            self.client.get_feature_flag("person-flag", "some-distinct-id", person_properties={"star": "sun"})
+        )
+
     @mock.patch("posthog.client.decide")
     @mock.patch("posthog.client.get")
     def test_flag_group_properties(self, patch_get, patch_decide):

posthog/utils.py

@@ -125,3 +125,43 @@ def convert_to_datetime_aware(date_obj):
     if date_obj.tzinfo is None:
         date_obj = date_obj.replace(tzinfo=timezone.utc)
     return date_obj
+
+
+def str_icontains(source, search):
+    """
+    Check if a string contains another string, ignoring case.
+
+    Args:
+        source: The string to search within
+        search: The substring to search for
+
+    Returns:
+        bool: True if search is a substring of source (case-insensitive), False otherwise
+
+    Examples:
+        >>> str_icontains("Hello World", "WORLD")
+        True
+        >>> str_icontains("Hello World", "python")
+        False
+    """
+    return str(search).casefold() in str(source).casefold()
+
+
+def str_iequals(value, comparand):
+    """
+    Check if a string equals another string, ignoring case.
+
+    Args:
+        value: The string to compare
+        comparand: The string to compare with
+
+    Returns:
+        bool: True if value and comparand are equal (case-insensitive), False otherwise
+
+    Examples:
+        >>> str_iequals("Hello World", "hello world")
+        True
+        >>> str_iequals("Hello World", "hello")
+        False
+    """
+    return str(value).casefold() == str(comparand).casefold()