feat(feature-flags): support quota limiting for feature flags (#195)

* haha okay

* tests workin

* format

* use case-sensitive comparisons

* omg LOL

* fix tests

* jeez

* this will probably work

* now do local eval

* okay

* yo

* formatting

* fix import order

* type check

* ai yi yi

* code review

* format

CHANGELOG.md

@@ -1,3 +1,10 @@
+## 3.15.0 - 2025-02-19
+
+1. Support quota-limited feature flags
+
+## 3.14.2 - 2025-02-19
+
+1. Evaluate feature flag payloads with case sensitivity correctly.  Fixes <https://github.com/PostHog/posthog-python/issues/178>
 
 ## 3.14.1 - 2025-02-18
 

posthog/client.py

@@ -600,6 +600,19 @@ class Client(object):
                         "To use feature flags, please set a personal_api_key "
                         "More information: https://posthog.com/docs/api/overview",
                     )
+            elif e.status == 402:
+                self.log.warning("[FEATURE FLAGS] PostHog feature flags quota limited")
+                # Reset all feature flag data when quota limited
+                self.feature_flags = []
+                self.feature_flags_by_key = {}
+                self.group_type_mapping = {}
+                self.cohorts = {}
+
+                if self.debug:
+                    raise APIError(
+                        status=402,
+                        message="PostHog feature flags quota limited",
+                    )
             else:
                 self.log.error(f"[FEATURE FLAGS] Error loading feature flags: {e}")
         except Exception as e:
@@ -822,7 +835,7 @@ class Client(object):
                     distinct_id, groups, person_properties, group_properties, disable_geoip
                 )
                 response = responses_and_payloads["featureFlags"].get(key, None)
-                payload = responses_and_payloads["featureFlagPayloads"].get(str(key).lower(), None)
+                payload = responses_and_payloads["featureFlagPayloads"].get(str(key), None)
             except Exception as e:
                 self.log.exception(f"[FEATURE FLAGS] Unable to get feature flags and payloads: {e}")
 
@@ -875,10 +888,14 @@ class Client(object):
         if self.feature_flags_by_key is None:
             return payload
 
-        flag_definition = self.feature_flags_by_key.get(key) or {}
-        flag_filters = flag_definition.get("filters") or {}
-        flag_payloads = flag_filters.get("payloads") or {}
-        payload = flag_payloads.get(str(match_value).lower(), None)
+        flag_definition = self.feature_flags_by_key.get(key)
+        if flag_definition:
+            flag_filters = flag_definition.get("filters") or {}
+            flag_payloads = flag_filters.get("payloads") or {}
+            # For boolean flags, convert True to "true"
+            # For multivariate flags, use the variant string as-is
+            lookup_value = "true" if isinstance(match_value, bool) and match_value else str(match_value)
+            payload = flag_payloads.get(lookup_value, None)
         return payload
 
     def get_all_flags(

posthog/request.py

@@ -68,7 +68,19 @@ def _process_response(
     log = logging.getLogger("posthog")
     if res.status_code == 200:
         log.debug(success_message)
-        return res.json() if return_json else res
+        response = res.json() if return_json else res
+        # Handle quota limited decide responses by raising a specific error
+        # NB: other services also put entries into the quotaLimited key, but right now we only care about feature flags
+        # since most of the other services handle quota limiting in other places in the application.
+        if (
+            isinstance(response, dict)
+            and "quotaLimited" in response
+            and isinstance(response["quotaLimited"], list)
+            and "feature_flags" in response["quotaLimited"]
+        ):
+            log.warning("PostHog feature flags quota limited")
+            raise QuotaLimitError(res.status_code, "Feature flags quota limited")
+        return response
     try:
         payload = res.json()
         log.debug("received response: %s", payload)
@@ -112,6 +124,10 @@ class APIError(Exception):
         return msg.format(self.message, self.status)
 
 
+class QuotaLimitError(APIError):
+    pass
+
+
 class DatetimeSerializer(json.JSONEncoder):
     def default(self, obj: Any):
         if isinstance(obj, (date, datetime)):

posthog/test/test_client.py

@@ -7,6 +7,7 @@ import mock
 import six
 
 from posthog.client import Client
+from posthog.request import APIError
 from posthog.test.test_utils import FAKE_TEST_API_KEY
 from posthog.version import VERSION
 
@@ -384,6 +385,25 @@ class TestClient(unittest.TestCase):
         assert "$feature/false-flag" not in msg["properties"]
         assert "$active_feature_flags" not in msg["properties"]
 
+    @mock.patch("posthog.client.get")
+    def test_load_feature_flags_quota_limited(self, patch_get):
+        mock_response = {
+            "type": "quota_limited",
+            "detail": "You have exceeded your feature flag request quota",
+            "code": "payment_required",
+        }
+        patch_get.side_effect = APIError(402, mock_response["detail"])
+
+        client = Client(FAKE_TEST_API_KEY, personal_api_key="test")
+        with self.assertLogs("posthog", level="WARNING") as logs:
+            client._load_feature_flags()
+
+            self.assertEqual(client.feature_flags, [])
+            self.assertEqual(client.feature_flags_by_key, {})
+            self.assertEqual(client.group_type_mapping, {})
+            self.assertEqual(client.cohorts, {})
+            self.assertIn("PostHog feature flags quota limited", logs.output[0])
+
     @mock.patch("posthog.client.decide")
     def test_dont_override_capture_with_local_flags(self, patch_decide):
         patch_decide.return_value = {"featureFlags": {"beta-feature": "random-variant"}}

posthog/test/test_feature_flags.py

@@ -4640,3 +4640,84 @@ class TestConsistency(unittest.TestCase):
                 self.assertEqual(feature_flag_match, results[i])
             else:
                 self.assertFalse(feature_flag_match)
+
+    @mock.patch("posthog.client.decide")
+    def test_feature_flag_case_sensitive(self, mock_decide):
+        mock_decide.return_value = {"featureFlags": {}}  # Ensure decide returns empty flags
+
+        client = Client(api_key=FAKE_TEST_API_KEY, personal_api_key=FAKE_TEST_API_KEY)
+        client.feature_flags = [
+            {
+                "id": 1,
+                "key": "Beta-Feature",
+                "active": True,
+                "filters": {
+                    "groups": [{"properties": [], "rollout_percentage": 100}],
+                },
+            }
+        ]
+
+        # Test that flag evaluation is case-sensitive
+        self.assertTrue(client.feature_enabled("Beta-Feature", "user1"))
+        self.assertFalse(client.feature_enabled("beta-feature", "user1"))
+        self.assertFalse(client.feature_enabled("BETA-FEATURE", "user1"))
+
+    @mock.patch("posthog.client.decide")
+    def test_feature_flag_payload_case_sensitive(self, mock_decide):
+        mock_decide.return_value = {
+            "featureFlags": {"Beta-Feature": True},
+            "featureFlagPayloads": {"Beta-Feature": {"some": "value"}},
+        }
+
+        client = Client(api_key=FAKE_TEST_API_KEY, personal_api_key=FAKE_TEST_API_KEY)
+        client.feature_flags = [
+            {
+                "id": 1,
+                "key": "Beta-Feature",
+                "active": True,
+                "filters": {
+                    "groups": [{"properties": [], "rollout_percentage": 100}],
+                    "payloads": {
+                        "true": {"some": "value"},
+                    },
+                },
+            }
+        ]
+
+        # Test that payload retrieval is case-sensitive
+        self.assertEqual(client.get_feature_flag_payload("Beta-Feature", "user1"), {"some": "value"})
+        self.assertIsNone(client.get_feature_flag_payload("beta-feature", "user1"))
+        self.assertIsNone(client.get_feature_flag_payload("BETA-FEATURE", "user1"))
+
+    @mock.patch("posthog.client.decide")
+    def test_feature_flag_case_sensitive_consistency(self, mock_decide):
+        mock_decide.return_value = {
+            "featureFlags": {"Beta-Feature": True},
+            "featureFlagPayloads": {"Beta-Feature": {"some": "value"}},
+        }
+
+        client = Client(api_key=FAKE_TEST_API_KEY, personal_api_key=FAKE_TEST_API_KEY)
+        client.feature_flags = [
+            {
+                "id": 1,
+                "key": "Beta-Feature",
+                "active": True,
+                "filters": {
+                    "groups": [{"properties": [], "rollout_percentage": 100}],
+                    "payloads": {
+                        "true": {"some": "value"},
+                    },
+                },
+            }
+        ]
+
+        # Test that flag evaluation and payload retrieval are consistently case-sensitive
+        # Only exact match should work
+        self.assertTrue(client.feature_enabled("Beta-Feature", "user1"))
+        self.assertEqual(client.get_feature_flag_payload("Beta-Feature", "user1"), {"some": "value"})
+
+        # Different cases should not match
+        test_cases = ["beta-feature", "BETA-FEATURE", "bEtA-FeAtUrE"]
+        for case in test_cases:
+            self.assertFalse(client.feature_enabled(case, "user1"))
+            self.assertIsNone(client.get_feature_flag_payload(case, "user1"))

posthog/test/test_request.py

@@ -2,10 +2,11 @@ import json
 import unittest
 from datetime import date, datetime
 
+import mock
 import pytest
 import requests
 
-from posthog.request import DatetimeSerializer, batch_post, determine_server_host
+from posthog.request import DatetimeSerializer, QuotaLimitError, batch_post, decide, determine_server_host
 from posthog.test.test_utils import TEST_API_KEY
 
 
@@ -44,6 +45,36 @@ class TestRequests(unittest.TestCase):
                 "key", batch=[{"distinct_id": "distinct_id", "event": "python event", "type": "track"}], timeout=0.0001
             )
 
+    def test_quota_limited_response(self):
+        mock_response = requests.Response()
+        mock_response.status_code = 200
+        mock_response._content = json.dumps(
+            {
+                "quotaLimited": ["feature_flags"],
+                "featureFlags": {},
+                "featureFlagPayloads": {},
+                "errorsWhileComputingFlags": False,
+            }
+        ).encode("utf-8")
+
+        with mock.patch("posthog.request._session.post", return_value=mock_response):
+            with self.assertRaises(QuotaLimitError) as cm:
+                decide("fake_key", "fake_host")
+
+            self.assertEqual(cm.exception.status, 200)
+            self.assertEqual(cm.exception.message, "Feature flags quota limited")
+
+    def test_normal_decide_response(self):
+        mock_response = requests.Response()
+        mock_response.status_code = 200
+        mock_response._content = json.dumps(
+            {"featureFlags": {"flag1": True}, "featureFlagPayloads": {}, "errorsWhileComputingFlags": False}
+        ).encode("utf-8")
+
+        with mock.patch("posthog.request._session.post", return_value=mock_response):
+            response = decide("fake_key", "fake_host")
+            self.assertEqual(response["featureFlags"], {"flag1": True})
+
 
 @pytest.mark.parametrize(
     "host, expected",

posthog/version.py

@@ -1,4 +1,4 @@
-VERSION = "3.14.1"
+VERSION = "3.15.0"
 
 if __name__ == "__main__":
     print(VERSION, end="")  # noqa: T201