handle DeciderFeatureNotFoundException with warnings.warn

Author: mrlevitas

reddit_decider/__init__.py

@@ -1,4 +1,5 @@
 import logging
+import warnings
 
 from copy import deepcopy
 from dataclasses import dataclass
@@ -13,6 +14,7 @@
 
 import rust_decider  # type: ignore
 from rust_decider import Decider as RustDecider
+from rust_decider import DeciderFeatureNotFoundException
 from rust_decider import DeciderInitException
 from rust_decider import DeciderException
 
@@ -346,6 +348,9 @@ def get_variant(
 
         try:
             decision = self._rs_decider.choose(experiment_name, ctx)
+        except DeciderFeatureNotFoundException as exc:
+            warnings.warn(exc)
+            return None
         except DeciderException as exc:
             logger.info(exc)
             return None

tests/decider_tests.py

@@ -3,6 +3,7 @@
 import logging
 import tempfile
 import unittest
+import warnings
 
 from unittest import mock
 
@@ -149,7 +150,7 @@ def test_make_object_for_context_and_decider_context(self):
         with self.assertLogs(logger, logging.WARN) as captured:
             # ensure no warnings are printed except for the dummy one
             # https://stackoverflow.com/a/61381576/4260179
-            logger.warn("Dummy warning")
+            logger.warning("Dummy warning")
             decider = decider_ctx_factory.make_object_for_context(name="test", span=self.mock_span)
             assert len(captured.records) == 1
             self.assertEqual(["WARNING:root:Dummy warning"], captured.output)
@@ -226,7 +227,7 @@ def test_make_object_for_context_and_decider_context_without_span(self):
         with self.assertLogs(logger, logging.WARN) as captured:
             # ensure no warnings are printed except for the dummy one
             # https://stackoverflow.com/a/61381576/4260179
-            logger.warn("Dummy warning")
+            logger.warning("Dummy warning")
 
             decider = decider_ctx_factory.make_object_for_context(name="test", span=None)
             assert len(captured.records) == 1
@@ -520,9 +521,22 @@ def test_none_returned_on_get_variant_call_with_experiment_not_found(self):
             decider = setup_decider(f, self.minimal_decider_context, self.mock_span, self.event_logger)
 
             self.assertEqual(self.event_logger.log.call_count, 0)
-            variant = decider.get_variant("anything")
+            with warnings.catch_warnings(record=True) as captured:
+                variant = decider.get_variant("anything")
+
+                # can't test warning log only shows up only once if `decider.get_variant("anything")`
+                # is called again due to bug in `catch_warnings` contextmanager
+                # see https://github.com/python/cpython/issues/73858
+                assert any(
+                    'Feature "anything" not found.'
+                    in str(x.message)
+                    for x in captured
+                )
             self.assertEqual(variant, None)
 
+            # no exposures should be triggered
+            self.assertEqual(self.event_logger.log.call_count, 0)
+
     def test_get_variant_without_expose(self):
         with create_temp_config_file(self.exp_base_config) as f:
             decider = setup_decider(f, self.dc, self.mock_span, self.event_logger)