add optional custom seed override for fractional op

Signed-off-by: Cole Bailey <[email protected]>

core/pkg/evaluator/fractional.go

@@ -64,12 +64,19 @@ func parseFractionalEvaluationData(values, data any) (string, []fractionalEvalua
 		bucketBy = fmt.Sprintf("%s%s", properties.FlagKey, targetingKey)
 	}
 
+	seed, ok := valuesArray[0].(string)
+	if ok {
+		valuesArray = valuesArray[1:]
+	} else {
+		seed = properties.FlagKey
+	}
+
 	feDistributions, err := parseFractionalEvaluationDistributions(valuesArray)
 	if err != nil {
 		return "", nil, err
 	}
 
-	return bucketBy, feDistributions, nil
+	return fmt.Sprintf("%s%s", seed, bucketBy), feDistributions, nil
 }
 
 func parseFractionalEvaluationDistributions(values []any) ([]fractionalEvaluationDistribution, error) {

core/pkg/evaluator/fractional_test.go

@@ -29,7 +29,8 @@ func TestFractionalEvaluation(t *testing.T) {
 											  },
 											  {
 												"fractional": [
-												  {"cat": [{"var": "$flagd.flagKey"}, {"var": "email"}]},
+												  {"var": "email"},
+												  {"var": "$flagd.flagKey"},
 												  [
 												  "red",
 												  25
@@ -69,7 +70,8 @@ func TestFractionalEvaluation(t *testing.T) {
 						},
 						{
 						"fractional": [
-							{"cat": ["my-seed", {"var": "email"}]},
+							{"var": "email"},
+							"my-seed",
 							["red",25],
 							["blue",25],
 							["green",25],
@@ -224,6 +226,59 @@ func TestFractionalEvaluation(t *testing.T) {
 			expectedValue:   "#FF0000",
 			expectedReason:  model.TargetingMatchReason,
 		},
+		"[email protected] with default seed": {
+			flags: Flags{
+				Flags: map[string]model.Flag{
+					"headerColor": {
+						State:          "ENABLED",
+						DefaultVariant: "red",
+						Variants: map[string]any{
+							"red":    "#FF0000",
+							"blue":   "#0000FF",
+							"green":  "#00FF00",
+							"yellow": "#FFFF00",
+						},
+						Targeting: []byte(`{
+							"if": [
+								{
+									"in": ["@faas.com", {
+										"var": ["email"]
+									}]
+								},
+								{
+									"fractional": [
+										{"var": "email"},
+										[
+										"red",
+										25
+									  	],
+									  	[
+										"blue",
+										25
+										],
+										[
+										"green",
+										25
+									  	],
+									  	[
+										"yellow",
+										25
+									  	]
+									]
+								}, null
+							]
+						}`),
+					},
+				},
+			},
+			flagKey: "headerColor",
+			context: map[string]any{
+				"email": "[email protected]",
+			},
+			expectedVariant: "green",
+			expectedValue:   "#00FF00",
+			expectedReason:  model.TargetingMatchReason,
+		},
 		"non even split": {
 			flags: Flags{
 				Flags: map[string]model.Flag{