default skip on, persist feature flags through session (#218)

* default to using skip

* Revert "default to using skip"

This reverts commit 2816867.

* implement default value and session feature flag consistency

* Delete contents.xcworkspacedata

---------

Co-authored-by: Mike <[email protected]>

StatsigInjections/StatsigInjections/StatsigInjections.swift

@@ -13,6 +13,14 @@ import Combine
 
     private let apiKey: String
     private let environment: StatsigEnvironment
+    // ensures feature flag values stay constant throughout the app session after they are used the first time, even if they are initialized to null
+    private var sessionValues = [String: Availabilty]()
+
+    private enum Availabilty {
+        case available(Bool)
+        // unavailable is the case for a new feature flag, or a first launch of the app with Statsig
+        case unavailable
+    }
 
     public enum Environment {
         case production
@@ -67,22 +75,37 @@ import Combine
                     if let error {
                         Console.shared.log("Statsig feature flags failed to initialize: \(error)")
                     }
-                    self?.newValuesSubject.send()
                     // intentionally not calling completion here since we do not want ff init to be blocking startup
                     // this may change if we need FF pre-launch
 //                    completion()
                 }
         }
         completion()
     }
-
-    private let newValuesSubject = PassthroughSubject<Void, Never>()
-    public var newValuesAvailablePublisher: AnyPublisher<Void, Never> {
-        newValuesSubject.eraseToAnyPublisher()
-    }
 
+    // https://docs.statsig.com/sdk/debugging
     public func isOn(feature: String) -> Bool? {
-        Statsig.checkGate(feature)
+        let featureGate = Statsig.getFeatureGate(feature)
+        let availability: Availabilty
+        if let existingAvailability = sessionValues[feature] {
+            // a featuregate value has already been set for this session
+            availability = existingAvailability
+        } else if featureGate.evaluationDetails.reason == .Recognized {
+            // a featuregate will be recognized if the feature gate has been fetched in previous Statsig inits (cache is non-empty)
+            availability = .available(featureGate.value)
+        } else {
+            // a featuregate will be unrecognized if the feature gate is new or this is first time initializing Statsig (cache would be empty)
+            availability = .unavailable
+        }
+        sessionValues[feature] = availability
+
+        switch availability {
+        case .available(let bool):
+            return bool
+        case .unavailable:
+            // defer to calling context for default value
+            return nil
+        }
     }
 
     public func value(feature: String) -> String? {

Utilities/Utilities/_Utils/_FeatureFlags/CompositeFeatureFlagsProvider.swift

@@ -12,12 +12,6 @@ import Combine
 public class CompositeFeatureFlagsProvider: NSObject & FeatureFlagsProtocol {
     public var local: FeatureFlagsProtocol?
     public var remote: FeatureFlagsProtocol?
-
-    public var newValuesAvailablePublisher: AnyPublisher<Void, Never> {
-        Publishers.Merge(local?.newValuesAvailablePublisher ?? Just(()).eraseToAnyPublisher(),
-                         remote?.newValuesAvailablePublisher ?? Just(()).eraseToAnyPublisher())
-            .eraseToAnyPublisher()
-    }
 
     public func refresh(completion: @escaping () -> Void) {
         if let local = local {

Utilities/Utilities/_Utils/_FeatureFlags/FeatureService.swift

@@ -17,15 +17,6 @@ public protocol FeatureFlagsProtocol {
     func isOn(feature: String) -> Bool?
 
     func customized() -> Bool
-
-    var newValuesAvailablePublisher: AnyPublisher<Void, Never> { get }
-}
-
-// default impl
-extension FeatureFlagsProtocol {
-    public var newValuesAvailablePublisher: AnyPublisher<Void, Never> {
-        return Just(()).eraseToAnyPublisher()
-    }
 }
 
 public class FeatureService {

dydx/dydxFormatter/dydxFormatter/_Utils/dydxFeatureFlag.swift

@@ -10,18 +10,28 @@ import Foundation
 import Utilities
 
 public enum dydxBoolFeatureFlag: String, CaseIterable {
-    case push_notification
     case force_mainnet
     case enable_app_rating
     case shouldUseSkip = "ff_skip_migration"
 
+    var defaultValue: Bool {
+        switch self {
+        case .force_mainnet:
+            return false
+        case .enable_app_rating:
+            return true
+        case .shouldUseSkip:
+            return true
+        }
+    }
+
     private static let obj = NSObject()
 
     public var isEnabled: Bool {
         if FeatureService.shared == nil {
             Console.shared.log("WARNING: FeatureService not yet set up.")
         }
-        return FeatureService.shared?.isOn(feature: rawValue) == true
+        return FeatureService.shared?.isOn(feature: rawValue) ?? defaultValue
     }
 
     public static var enabledFlags: [String] {

dydx/dydxStateManager/dydxStateManager/AbacusStateManager.swift

@@ -158,6 +158,7 @@ public final class AbacusStateManager: NSObject {
 
         appConfigs.onboardingConfigs.squidVersion = OnboardingConfigs.SquidVersion.v2
         appConfigs.onboardingConfigs.alchemyApiKey = CredientialConfig.shared.credential(for: "alchemyApiKey")
+        StatsigConfig.shared.useSkip = dydxBoolFeatureFlag.shouldUseSkip.isEnabled
 
         return AsyncAbacusStateManagerV2(
             deploymentUri: deploymentUri,
@@ -177,8 +178,6 @@ public final class AbacusStateManager: NSObject {
         _ = CosmoJavascript.shared
         _ = foregroundToken
         _ = backgroundToken
-
-        startListeningForFeatureFlagChanges()
     }
 
     private func start() {
@@ -207,14 +206,6 @@ public final class AbacusStateManager: NSObject {
         isStarted = true
     }
 
-    private func startListeningForFeatureFlagChanges() {
-        FeatureService.shared?.newValuesAvailablePublisher
-            .sink {
-                StatsigConfig.shared.useSkip = dydxBoolFeatureFlag.shouldUseSkip.isEnabled
-            }
-            .store(in: &cancellables)
-    }
-
     public func setMarket(market: String?) {
         asyncStateManager.market = market
     }