fix(DataStore): created and deleted model on one device appears as created on the other (#3554)

* fix(DataStore): created and deleted model on one device appears as created on the other (#3553)

* fix(DataStore): created and deleted model on one device appears as created on the other #3553

Co-authored-by: Di Wu <github@wudi.me>

* fix(DataStore): created and deleted model on one device appears as created on the other #3553

---------

Co-authored-by: Di Wu <github@wudi.me>

Author: MuniekMg

AmplifyPlugins/DataStore/Sources/AWSDataStorePlugin/Sync/SubscriptionSync/ReconcileAndLocalSave/RemoteSyncReconciler.swift

@@ -33,26 +33,41 @@ struct RemoteSyncReconciler {
         }
     }
 
-
     /// Reconciles the incoming `remoteModels` against the local metadata to get the disposition
     ///
+    /// GroupBy the remoteModels by model identifier and apply only the latest version of the remoteModel
+    ///
     /// - Parameters:
     ///   - remoteModels: models retrieved from the remote store
     ///   - localMetadatas: metadata retrieved from the local store
     /// - Returns: disposition of models to apply locally
-    static func getDispositions(_ remoteModels: [RemoteModel],
-                                localMetadatas: [LocalMetadata]) -> [Disposition] {
-        guard !remoteModels.isEmpty else {
+    static func getDispositions(
+        _ remoteModels: [RemoteModel],
+        localMetadatas: [LocalMetadata]
+    ) -> [Disposition] {
+        let remoteModelsGroupByIdentifier = remoteModels.reduce([String: [RemoteModel]]()) {
+            $0.merging([
+                $1.model.identifier: ($0[$1.model.identifier] ?? []) + [$1]
+            ], uniquingKeysWith: { $1 })
+        }
+        
+        let optimizedRemoteModels = remoteModelsGroupByIdentifier.values.compactMap {
+            $0.sorted(by: { $0.syncMetadata.version > $1.syncMetadata.version }).first
+        }
+        
+        guard !optimizedRemoteModels.isEmpty else {
             return []
         }
-
+        
         guard !localMetadatas.isEmpty else {
-            return remoteModels.compactMap { getDisposition($0, localMetadata: nil) }
+            return optimizedRemoteModels.compactMap { getDisposition($0, localMetadata: nil) }
         }
-
-        let metadataBymodelId = localMetadatas.reduce(into: [:]) { $0[$1.modelId] = $1 }
-        let dispositions = remoteModels.compactMap { getDisposition($0, localMetadata: metadataBymodelId[$0.model.identifier]) }
-
+        
+        let metadataByModelId = localMetadatas.reduce(into: [:]) { $0[$1.modelId] = $1 }
+        let dispositions = optimizedRemoteModels.compactMap {
+            getDisposition($0, localMetadata: metadataByModelId[$0.model.identifier])
+        }
+        
         return dispositions
     }
 

AmplifyPlugins/DataStore/Tests/AWSDataStorePluginTests/Sync/SubscriptionSync/RemoteSyncReconcilerTests.swift

@@ -179,6 +179,33 @@ class RemoteSyncReconcilerTests: XCTestCase {
         }
         waitForExpectations(timeout: 1)
     }
+    
+    func testGetDispositions_emptyLocal_singleModelAddedAndDeleted() {
+        let sameId = UUID().uuidString
+        
+        let remoteModels = [
+            makeRemoteModel(modelId: sameId, deleted: false, version: 1),
+            makeRemoteModel(modelId: sameId, deleted: true, version: 2)
+        ]
+
+        let dispositions = RemoteSyncReconciler.getDispositions(remoteModels, localMetadatas: [])
+
+        XCTAssertTrue(dispositions.isEmpty)
+    }
+    
+    func testGetDispositions_emptyLocal_oneModelAdded_SecondModelAddedAndDeleted() {
+        let sameId = UUID().uuidString
+        
+        let remoteModels = [
+            makeRemoteModel(deleted: false, version: 1),
+            makeRemoteModel(modelId: sameId, deleted: false, version: 1),
+            makeRemoteModel(modelId: sameId, deleted: true, version: 2)
+        ]
+
+        let dispositions = RemoteSyncReconciler.getDispositions(remoteModels, localMetadatas: [])
+
+        XCTAssertTrue(dispositions.count == 1)
+    }
 
     // MARK: - Utilities