fix(@aws-amplify/datastore): correctly processing Delta Sync query response in RN

packages/datastore/__tests__/Merger.test.ts

@@ -0,0 +1,145 @@
+import { ModelMerger } from '../src/sync/merger';
+import { PersistentModelConstructor } from '../src/';
+import {
+	DataStore as DataStoreType,
+	initSchema as initSchemaType,
+} from '../src/datastore/datastore';
+import { Model as ModelType, testSchema } from './helpers';
+
+let initSchema: typeof initSchemaType;
+let DataStore: typeof DataStoreType;
+let Storage: any;
+const ownSymbol = Symbol('sync');
+
+describe('ModelMerger tests', () => {
+	let modelMerger: ModelMerger;
+	let Model: PersistentModelConstructor<InstanceType<typeof ModelType>>;
+
+	describe('mergePage', () => {
+		beforeAll(async () => {
+			({ initSchema, DataStore } = require('../src/datastore/datastore'));
+			({ Model } = initSchema(testSchema()) as {
+				Model: PersistentModelConstructor<ModelType>;
+			});
+
+			await DataStore.start();
+
+			// mergePage doesn't rely on the outbox, so it doesn't need to be mocked
+			const outbox = (() => {}) as any;
+
+			Storage = (DataStore as any).storage;
+			modelMerger = new ModelMerger(outbox, ownSymbol);
+		});
+
+		test('delete after create should result in delete', async () => {
+			const modelId = 'ce408429-d667-4606-bb4f-3d7e0a8e5938';
+
+			const items = [
+				{
+					id: modelId,
+					field1: 'Create',
+					optionalField1: null,
+					_version: 1,
+					_lastChangedAt: 1619627611860,
+					_deleted: null,
+				},
+				{
+					id: modelId,
+					field1: 'Create',
+					optionalField1: null,
+					_version: 2,
+					_lastChangedAt: 1619627619017,
+					_deleted: true,
+				},
+			];
+
+			await Storage.runExclusive(async storage => {
+				await modelMerger.mergePage(storage, Model, items);
+			});
+
+			const record = await DataStore.query(Model, modelId);
+
+			expect(record).toBeUndefined();
+		});
+
+		test('update after create should persist data from update', async () => {
+			const modelId = '15739024-910d-4c1e-b401-65f5f7838f42';
+
+			const items = [
+				{
+					id: modelId,
+					field1: 'Create',
+					optionalField1: null,
+					_version: 1,
+					_lastChangedAt: 1619627611860,
+					_deleted: null,
+				},
+				{
+					id: modelId,
+					field1: 'Update',
+					optionalField1: null,
+					_version: 2,
+					_lastChangedAt: 1619627619017,
+					_deleted: null,
+				},
+				{
+					id: modelId,
+					field1: 'Another Update',
+					optionalField1: 'Optional',
+					_version: 2,
+					_lastChangedAt: 1619627621329,
+					_deleted: null,
+				},
+			];
+
+			await Storage.runExclusive(async storage => {
+				await modelMerger.mergePage(storage, Model, items);
+			});
+
+			const record = await DataStore.query(Model, modelId);
+
+			expect(record.field1).toEqual('Another Update');
+			expect(record.optionalField1).toEqual('Optional');
+		});
+
+		test('create > delete > create => create', async () => {
+			const modelId = '3d2d9d63-a561-4a29-af29-fd4ef465a5ee';
+
+			const items = [
+				{
+					id: modelId,
+					field1: 'Create',
+					optionalField1: null,
+					_version: 1,
+					_lastChangedAt: 1619627611860,
+					_deleted: null,
+				},
+				{
+					id: modelId,
+					field1: 'Create',
+					optionalField1: null,
+					_version: 2,
+					_lastChangedAt: 1619627619017,
+					_deleted: true,
+				},
+				{
+					id: modelId,
+					field1: 'New Create with the same id',
+					optionalField1: null,
+					_version: 1,
+					_lastChangedAt: 1619627621329,
+					_deleted: null,
+				},
+			];
+
+			await Storage.runExclusive(async storage => {
+				await modelMerger.mergePage(storage, Model, items);
+			});
+
+			const record = await DataStore.query(Model, modelId);
+
+			expect(record).not.toBeUndefined();
+			expect(record.field1).toEqual('New Create with the same id');
+		});
+	});
+});

packages/datastore/src/sync/merger.ts

@@ -37,7 +37,16 @@ class ModelMerger {
 		modelConstructor: PersistentModelConstructor<any>,
 		items: ModelInstanceMetadata[]
 	): Promise<[ModelInstanceMetadata, OpType][]> {
-		return await storage.batchSave(modelConstructor, items, this.ownSymbol);
+		const itemsMap: Map<string, ModelInstanceMetadata> = new Map();
+
+		for (const item of items) {
+			// merge items by model id. Latest record for a given id remains.
+			itemsMap.set(item.id, item);
+		}
+
+		const page = [...itemsMap.values()];
+
+		return await storage.batchSave(modelConstructor, page, this.ownSymbol);
 	}
 }