fix: handle preview initial sync once per device

Handle preview initial sync once per device (in some cases PubNub reports the device multiple times). Also prepare all the files once per platform, not per each device.

Author: rosen-vladimirov

lib/controllers/preview-app-controller.ts

@@ -9,7 +9,8 @@ import { PrepareDataService } from "../services/prepare-data-service";
 import { PreviewAppLiveSyncEvents } from "../services/livesync/playground/preview-app-constants";
 
 export class PreviewAppController extends EventEmitter implements IPreviewAppController {
-	private deviceInitializationPromise: IDictionary<Promise<FilesPayload>> = {};
+	private deviceInitializationPromise: IDictionary<boolean> = {};
+	private platformPrepareHandlers: IDictionary<boolean> = {};
 	private promise = Promise.resolve();
 
 	constructor(
@@ -49,9 +50,14 @@ export class PreviewAppController extends EventEmitter implements IPreviewAppCon
 				}
 
 				if (this.deviceInitializationPromise[device.id]) {
-					return this.deviceInitializationPromise[device.id];
+					// In some cases devices are reported several times during initialization.
+					// In case we are already preparing the sending of initial files, disregard consecutive requests for initial files
+					// until we send the files we are currently preparing.
+					return null;
 				}
 
+				this.deviceInitializationPromise[device.id] = true;
+
 				if (device.uniqueId) {
 					await this.$analyticsService.trackEventActionInGoogleAnalytics({
 						action: TrackActionNames.PreviewAppData,
@@ -68,20 +74,25 @@ export class PreviewAppController extends EventEmitter implements IPreviewAppCon
 
 				await this.$previewAppPluginsService.comparePluginsOnDevice(data, device);
 
-				this.$prepareController.on(PREPARE_READY_EVENT_NAME, async currentPrepareData => {
-					await this.handlePrepareReadyEvent(data, currentPrepareData.hmrData, currentPrepareData.files, device.platform);
-				});
+				if (!this.platformPrepareHandlers[device.platform]) {
+					// TODO: Unset this property once the preview operation for this platform is stopped
+					this.platformPrepareHandlers[device.platform] = true;
+
+					// TODO: Remove the handler once the preview operation for this platform is stopped
+					this.$prepareController.on(PREPARE_READY_EVENT_NAME, async currentPrepareData => {
+						await this.handlePrepareReadyEvent(data, currentPrepareData.hmrData, currentPrepareData.files, device.platform);
+					});
 
-				if (!data.env) { data.env = { }; }
+				}
+
+				data.env = data.env || {};
 				data.env.externals = this.$previewAppPluginsService.getExternalPlugins(device);
 
-				const prepareData = this.$prepareDataService.getPrepareData(data.projectDir, device.platform.toLowerCase(),  { ...data, nativePrepare: { skipNativePrepare: true }, watch: true });
+				const prepareData = this.$prepareDataService.getPrepareData(data.projectDir, device.platform.toLowerCase(), { ...data, nativePrepare: { skipNativePrepare: true }, watch: true });
 				await this.$prepareController.prepare(prepareData);
 
-				this.deviceInitializationPromise[device.id] = this.getInitialFilesForPlatformSafe(data, device.platform);
-
 				try {
-					const payloads = await this.deviceInitializationPromise[device.id];
+					const payloads = await this.getInitialFilesForPlatformSafe(data, device.platform);
 					return payloads;
 				} finally {
 					this.deviceInitializationPromise[device.id] = null;
@@ -116,7 +127,7 @@ export class PreviewAppController extends EventEmitter implements IPreviewAppCon
 						if (status === HmrConstants.HMR_ERROR_STATUS) {
 							const originalUseHotModuleReload = data.useHotModuleReload;
 							data.useHotModuleReload = false;
-							await this.syncFilesForPlatformSafe(data, { filesToSync: platformHmrData.fallbackFiles }, platform, previewDevice.id );
+							await this.syncFilesForPlatformSafe(data, { filesToSync: platformHmrData.fallbackFiles }, platform, previewDevice.id);
 							data.useHotModuleReload = originalUseHotModuleReload;
 						}
 					}));