fix: Do not convert string variant results into bool (#87)

The words "true" and "false" are valid variant keys. It's incorrect to convert them to `true` and `false`. This could result in a case where `isEnabled` returns `false` when in fact, it's `true` but the variant selected is named "false".

Added a test to confirm this change.

Author: haacked

feature_flags_test.go

@@ -947,7 +947,7 @@ func TestGetFeatureFlagPayload(t *testing.T) {
 
 func TestGetRemoteConfigPayload(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			w.Write([]byte(fixture("test-remote-config.json")))
+		w.Write([]byte(fixture("test-remote-config.json")))
 	}))
 
 	defer server.Close()
@@ -971,7 +971,6 @@ func TestGetRemoteConfigPayload(t *testing.T) {
 	}
 }
 
-
 func TestFlagWithVariantOverrides(t *testing.T) {
 
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -4646,3 +4645,71 @@ func TestFetchFlagsFails(t *testing.T) {
 		t.Error("Expected to be called", expectedCalls, "times but got", actualCalls)
 	}
 }
+
+func TestFeatureFlagWithFalseVariant(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if strings.HasPrefix(r.URL.Path, "/api/feature_flag/local_evaluation") {
+			w.Write([]byte(`{
+				"flags": [{
+					"id": 719,
+					"name": "",
+					"key": "test-flag",
+					"filters": {
+						"groups": [
+							{
+								"properties": [],
+								"rollout_percentage": 100
+							}
+						],
+						"multivariate": {
+							"variants": [
+								{"key": "false", "rollout_percentage": 50},
+								{"key": "true", "rollout_percentage": 50}
+							]
+						}
+					},
+					"deleted": false,
+					"active": true,
+					"is_simple_flag": false,
+					"rollout_percentage": null
+				}]
+			}`))
+		}
+	}))
+	defer server.Close()
+
+	client, _ := NewWithConfig("Csyjlnlun3OzyNJAafdlv", Config{
+		PersonalApiKey: "some very secret key",
+		Endpoint:       server.URL,
+	})
+	defer client.Close()
+
+	// Test GetFeatureFlag - should return the variant name "false"
+	variant, err := client.GetFeatureFlag(
+		FeatureFlagPayload{
+			Key:        "test-flag",
+			DistinctId: "test-id",
+		},
+	)
+	if err != nil {
+		t.Error("Unexpected error:", err)
+	}
+	if variant != "false" {
+		t.Errorf("Expected variant 'false', got: %v", variant)
+	}
+
+	// Test IsFeatureEnabled - should return the variant name "false"
+	// This will fail with the current implementation because it incorrectly converts "false" to false
+	isEnabled, err := client.IsFeatureEnabled(
+		FeatureFlagPayload{
+			Key:        "test-flag",
+			DistinctId: "test-id",
+		},
+	)
+	if err != nil {
+		t.Error("Unexpected error:", err)
+	}
+	if isEnabled != "false" {
+		t.Errorf("Expected variant 'false', got: %v", isEnabled)
+	}
+}

featureflags.go

@@ -1009,10 +1009,8 @@ func (poller *FeatureFlagsPoller) getFeatureFlagVariant(featureFlag FeatureFlag,
 		}
 
 		for flagKey, flagValue := range featureFlagVariants.FeatureFlags {
-			flagValueString := fmt.Sprintf("%v", flagValue)
-			if key == flagKey && flagValueString != "false" {
-				result = flagValueString
-				break
+			if key == flagKey {
+				return flagValue, nil
 			}
 		}
 		return result, nil

posthog.go

@@ -287,12 +287,6 @@ func (c *client) IsFeatureEnabled(flagConfig FeatureFlagPayload) (interface{}, e
 		return nil, err
 	}
 
-	if result == "false" {
-		result = false
-	} else if result == "true" {
-		result = true
-	}
-
 	return result, nil
 }
 

posthog_test.go

@@ -842,7 +842,7 @@ func TestIsFeatureEnabled(t *testing.T) {
 				DistinctId: "user789",
 			},
 			mockResponse:   `{"featureFlags": {"test-flag": "true"}}`,
-			expectedResult: true,
+			expectedResult: "true",
 		},
 		{
 			name: "Feature flag is a string 'false'",
@@ -851,7 +851,7 @@ func TestIsFeatureEnabled(t *testing.T) {
 				DistinctId: "user101",
 			},
 			mockResponse:   `{"featureFlags": {"test-flag": "false"}}`,
-			expectedResult: false,
+			expectedResult: "false",
 		},
 		{
 			name: "Feature flag is a variant string",