feat!: Use FeatureValue.priority for multivariate evaluations (#268)

Author: khvn26

.gitmodules

@@ -1,4 +1,4 @@
 [submodule "tests/engine_tests/engine-test-data"]
 	path = tests/engine_tests/engine-test-data
 	url = https://github.com/flagsmith/engine-test-data.git
-	tag = v2.2.0
+	tag = v2.4.0

flag_engine/context/types.py

@@ -24,6 +24,7 @@ class EnvironmentContext(TypedDict):
 class FeatureValue(TypedDict):
     value: Any
     weight: float
+    priority: int
 
 
 class IdentityContext(TypedDict):

flag_engine/segments/evaluator.py

@@ -131,12 +131,12 @@ def get_flag_result_from_feature_context(
             [feature_context["key"], key]
         )
 
-        # We expect `variants` to be pre-sorted in order of persistence. This gives us a
-        # way to ensure that the same value is returned every time we use the same
-        # percentage value.
         start_percentage = 0.0
 
-        for variant in variants:
+        for variant in sorted(
+            variants,
+            key=operator.itemgetter("priority"),
+        ):
             limit = (weight := variant["weight"]) + start_percentage
             if start_percentage <= percentage_value < limit:
                 return {

tests/engine_tests/engine-test-data

@@ -855,8 +855,8 @@ def test_get_flag_result_from_feature_context__calls_returns_expected(
         "name": "my_feature",
         "value": "control",
         "variants": [
-            {"value": "foo", "weight": 30},
-            {"value": "bar", "weight": 30},
+            {"value": "foo", "weight": 30, "priority": 1},
+            {"value": "bar", "weight": 30, "priority": 2},
         ],
     }
 
@@ -897,8 +897,8 @@ def test_get_flag_result_from_feature_context__null_key__calls_returns_expected(
         "name": "my_feature",
         "value": "control",
         "variants": [
-            {"value": "foo", "weight": 30},
-            {"value": "bar", "weight": 30},
+            {"value": "foo", "weight": 30, "priority": 1},
+            {"value": "bar", "weight": 30, "priority": 2},
         ],
     }