fix: Fix data store mutation when restoring network (#1345)

Fixes an issue in DataStore where it dropped consecutive updates to a model if
received while the network was not connected. As part of this fix, we
simplified the OutgoingMutationQueue state machine and cleaned up potential
race conditions in state synchronization between RemoteSyncEngine and
OutgoingMutationQueue.

- fix: Fix data races in MutationRetryNotifier encountered in some test
  situations. It's unclear whether this would be encountered in production
  since the production model includes additional queue protections.

- fix: Fix retain cycles in RemoteSyncEngine

- fix: RemoteSyncEngine now correctly sets up publisher notifications for
  custom reachability publishers

- test: Change SyncEngineTestBase reachabilityPublisher to be
  CurrentValueSubject

- test: DataStore sync tests can now specify an on-disk SQLite file rather than
  only an in-memory SQLite database to back the DataStore.

- test: API category can now specify a custom reachability publisher

- test: fix Amplify.reset(). This includes explicitly declaring Resettable
  conformance for a few types that were missing it, protecting `Logger` with an
  AtomicValue since it is used during the actual reset() flow, and adding
  verbose logging to reset flows to help identify race conditions or deadlocks
  in future. Amplify.reset() is also now synchronous, although Resettable.reset()
  still accepts a callback.

- test: Overall DataStore test stability fixes

Author: palpatim

.gitignore

@@ -50,3 +50,24 @@ amplifyconfiguration.json
 credentials-mc.json
 
 fastlane/report.xml
+
+# Amplify artifacts, such as used for integ tests
+amplify
+amplify/\#current-cloud-backend
+amplify/.config/local-*
+amplify/logs
+amplify/mock-data
+amplify/backend/amplify-meta.json
+amplify/backend/awscloudformation
+amplify/backend/.temp
+build/
+dist/
+node_modules/
+aws-exports.js
+awsconfiguration.json
+amplifyconfiguration.json
+amplifyconfiguration.dart
+amplify-build-config.json
+amplify-gradle-config.json
+amplifytools.xcconfig
+.secret-*

Amplify/Amplify.swift

@@ -30,10 +30,21 @@ public class Amplify {
     public static internal(set) var Auth = AuthCategory()
     public static internal(set) var DataStore = DataStoreCategory()
     public static internal(set) var Hub = HubCategory()
-    public static internal(set) var Logging = LoggingCategory()
     public static internal(set) var Predictions = PredictionsCategory()
     public static internal(set) var Storage = StorageCategory()
 
+    // Special case category. We protect this with an AtomicValue because it is used by reset()
+    // methods during setup & teardown of tests
+    public static internal(set) var Logging: LoggingCategory {
+        get {
+            loggingAtomic.get()
+        }
+        set {
+            loggingAtomic.set(newValue)
+        }
+    }
+    private static let loggingAtomic = AtomicValue<LoggingCategory>(initialValue: LoggingCategory())
+
     /// Adds `plugin` to the Analytics category
     ///
     /// - Parameter plugin: The AnalyticsCategoryPlugin to add

Amplify/Categories/API/Internal/APICategory+Resettable.swift

@@ -13,12 +13,18 @@ extension AmplifyAPICategory: Resettable {
         let group = DispatchGroup()
 
         for plugin in plugins.values {
+            log.verbose("Resetting \(categoryType) plugin")
             group.enter()
-            plugin.reset { group.leave() }
+            plugin.reset {
+                self.log.verbose("Resetting \(self.categoryType) plugin: finished")
+                group.leave()
+            }
         }
 
+        log.verbose("Resetting ModelRegistry and ModelListDecoderRegistry")
         ModelRegistry.reset()
         ModelListDecoderRegistry.reset()
+        log.verbose("Resetting ModelRegistry and ModelListDecoderRegistry: finished")
 
         group.wait()
 

Amplify/Categories/Analytics/Internal/AnalyticsCategory+Resettable.swift

@@ -13,8 +13,12 @@ extension AnalyticsCategory: Resettable {
         let group = DispatchGroup()
 
         for plugin in plugins.values {
+            log.verbose("Resetting \(categoryType) plugin")
             group.enter()
-            plugin.reset { group.leave() }
+            plugin.reset {
+                self.log.verbose("Resetting \(self.categoryType) plugin: finished")
+                group.leave()
+            }
         }
 
         group.wait()

Amplify/Categories/Auth/Internal/AuthCategory+Resettable.swift

@@ -13,8 +13,12 @@ extension AuthCategory: Resettable {
         let group = DispatchGroup()
 
         for plugin in plugins.values {
+            log.verbose("Resetting \(categoryType) plugin")
             group.enter()
-            plugin.reset { group.leave() }
+            plugin.reset {
+                self.log.verbose("Resetting \(self.categoryType) plugin: finished")
+                group.leave()
+            }
         }
 
         group.wait()

Amplify/Categories/DataStore/Internal/DataStoreCategory+Resettable.swift

@@ -13,12 +13,18 @@ extension DataStoreCategory: Resettable {
         let group = DispatchGroup()
 
         for plugin in plugins.values {
+            log.verbose("Resetting \(categoryType) plugin")
             group.enter()
-            plugin.reset { group.leave() }
+            plugin.reset {
+                self.log.verbose("Resetting \(self.categoryType) plugin: finished")
+                group.leave()
+            }
         }
 
+        log.verbose("Resetting ModelRegistry and ModelListDecoderRegistry")
         ModelRegistry.reset()
         ModelListDecoderRegistry.reset()
+        log.verbose("Resetting ModelRegistry and ModelListDecoderRegistry: finished")
 
         group.wait()
 

Amplify/Categories/Hub/Internal/HubCategory+Resettable.swift

@@ -13,8 +13,12 @@ extension HubCategory: Resettable {
         let group = DispatchGroup()
 
         for plugin in plugins.values {
+            log.verbose("Resetting \(categoryType) plugin")
             group.enter()
-            plugin.reset { group.leave() }
+            plugin.reset {
+                self.log.verbose("Resetting \(self.categoryType) plugin: finished")
+                group.leave()
+            }
         }
 
         group.wait()

Amplify/Categories/Logging/Internal/LoggingCategory+Resettable.swift

@@ -10,12 +10,14 @@ import Foundation
 extension LoggingCategory: Resettable {
 
     public func reset(onComplete: @escaping BasicClosure) {
+        log.verbose("Resetting \(categoryType) plugin: no 'finish' message will be logged")
         concurrencyQueue.sync {
             let group = DispatchGroup()
 
             group.enter()
-
-            plugin.reset { group.leave() }
+            plugin.reset {
+                group.leave()
+            }
 
             group.wait()
 

Amplify/Categories/Predictions/Internal/PredictionsCategory+Resettable.swift

@@ -13,8 +13,12 @@ extension PredictionsCategory: Resettable {
         let group = DispatchGroup()
 
         for plugin in plugins.values {
+            log.verbose("Resetting \(categoryType) plugin")
             group.enter()
-            plugin.reset { group.leave() }
+            plugin.reset {
+                self.log.verbose("Resetting \(self.categoryType) plugin: finished")
+                group.leave()
+            }
         }
 
         group.wait()

Amplify/Categories/Storage/Internal/StorageCategory+Resettable.swift

@@ -13,8 +13,12 @@ extension StorageCategory: Resettable {
         let group = DispatchGroup()
 
         for plugin in plugins.values {
+            log.verbose("Resetting \(categoryType) plugin")
             group.enter()
-            plugin.reset { group.leave() }
+            plugin.reset {
+                self.log.verbose("Resetting \(self.categoryType) plugin: finished")
+                group.leave()
+            }
         }
 
         group.wait()