fix(ExperimentWhitelistService): Fix finding variation by key (#155)

Previously, GetDecision of ExperimentWhitelistService was incorrectly using variation key to look up variations in the Variations map of an Experiment struct, in which keys are variation IDs, not variation keys. 

With this fix, we iterate over variations to find the one with the desired key. To avoid needing to search all variations, we can add a map keyed by variation key as a follow up.

Author: mjc1283

pkg/decision/experiment_whitelist_service.go

@@ -47,13 +47,16 @@ func (s ExperimentWhitelistService) GetDecision(decisionContext ExperimentDecisi
 		return decision, nil
 	}
 
-	variation, ok := decisionContext.Experiment.Variations[variationKey]
-	if !ok {
-		decision.Reason = reasons.InvalidWhitelistVariationAssignment
-		return decision, nil
+	// TODO(Matt): Add a VariationsByKey map to the Experiment struct, and use it to look up Variation by key
+	for _, variation := range decisionContext.Experiment.Variations {
+		variation := variation
+		if variation.Key == variationKey {
+			decision.Reason = reasons.WhitelistVariationAssignmentFound
+			decision.Variation = &variation
+			return decision, nil
+		}
 	}
 
-	decision.Reason = reasons.WhitelistVariationAssignmentFound
-	decision.Variation = &variation
+	decision.Reason = reasons.InvalidWhitelistVariationAssignment
 	return decision, nil
 }

pkg/decision/helpers_test.go

@@ -226,7 +226,7 @@ var testTargetedExp1116 = entities.Experiment{
 // Experiment with a whitelist
 const testExpWhitelistKey = "test_experiment_whitelist"
 
-var testExpWhitelistVar2229 = entities.Variation{ID: "2229", Key: "2229"}
+var testExpWhitelistVar2229 = entities.Variation{ID: "2229", Key: "var_2229"}
 var testExpWhitelist = entities.Experiment{
 	ID:  "1117",
 	Key: testExpWhitelistKey,
@@ -237,8 +237,8 @@ var testExpWhitelist = entities.Experiment{
 		entities.Range{EntityID: "2229", EndOfRange: 10000},
 	},
 	Whitelist: map[string]string{
-		"test_user_1": "2229",
-		// Note: this is an invalid entry, there is no variation 2230 in this experiment
-		"test_user_2": "2230",
+		"test_user_1": "var_2229",
+		// Note: this is an invalid entry, there is no variation with key "var_2230" in this experiment
+		"test_user_2": "var_2230",
 	},
 }