fix: handle previewAppLiveSyncError event in CLI

Currently the `previewAppLiveSyncError` event is handled only when CLI is used as a library. Add handler when CLI is used from command line and use the same workflow in both cases.
Attach to the event every time when a new operation is started. Currently, once LiveSync is stopped, we've removed all handlers and we were never attaching them again. Now we rely on the isInitialized property, so we'll attach the event handler whenever it is needed.

Author: rosen-vladimirov

lib/commands/preview.ts

@@ -19,17 +19,11 @@ export class PreviewCommand implements ICommand {
 			this.$logger.info(message);
 		});
 
-		await this.$liveSyncService.liveSync([], {
-			syncToPreviewApp: true,
-			projectDir: this.$projectData.projectDir,
-			skipWatcher: !this.$options.watch,
-			watchAllFiles: this.$options.syncAllFiles,
-			clean: this.$options.clean,
+		await this.$liveSyncService.liveSyncToPreviewApp({
 			bundle: !!this.$options.bundle,
-			release: this.$options.release,
-			env: this.$options.env,
-			timeout: this.$options.timeout,
-			useHotModuleReload: this.$options.hmr
+			useHotModuleReload: this.$options.hmr,
+			projectDir: this.$projectData.projectDir,
+			env: this.$options.env
 		});
 
 		await this.$previewQrCodeService.printLiveSyncQrCode({ useHotModuleReload: this.$options.hmr, link: this.$options.link });

lib/definitions/livesync.d.ts

@@ -242,6 +242,13 @@ interface ILiveSyncService {
 	 */
 	liveSync(deviceDescriptors: ILiveSyncDeviceInfo[], liveSyncData: ILiveSyncInfo): Promise<void>;
 
+	/**
+	 * Starts LiveSync operation to Preview app.
+	 * @param {IPreviewAppLiveSyncData} data Describes information about the current operation.
+	 * @returns {Promise<IQrCodeImageData>} Data of the QR code that should be used to start the LiveSync operation.
+	 */
+	liveSyncToPreviewApp(data: IPreviewAppLiveSyncData): Promise<IQrCodeImageData>;
+
 	/**
 	 * Stops LiveSync operation for specified directory.
 	 * @param {string} projectDir The directory for which to stop the operation.

lib/services/livesync/livesync-service.ts

@@ -137,12 +137,13 @@ export class LiveSyncService extends EventEmitter implements IDebugLiveSyncServi
 		return currentDescriptors || [];
 	}
 
-	@cache()
 	private attachToPreviewAppLiveSyncError(): void {
-		this.$previewAppLiveSyncService.on(LiveSyncEvents.previewAppLiveSyncError, liveSyncData => {
-			this.$logger.error(liveSyncData.error);
-			this.emit(LiveSyncEvents.previewAppLiveSyncError, liveSyncData);
-		});
+		if (!this.$usbLiveSyncService.isInitialized) {
+			this.$previewAppLiveSyncService.on(LiveSyncEvents.previewAppLiveSyncError, liveSyncData => {
+				this.$logger.error(liveSyncData.error);
+				this.emit(LiveSyncEvents.previewAppLiveSyncError, liveSyncData);
+			});
+		}
 	}
 
 	private handleWarnings(liveSyncData: ILiveSyncInfo, projectData: IProjectData) {

test/stubs.ts

@@ -661,6 +661,10 @@ export class DebugServiceStub extends EventEmitter implements IDeviceDebugServic
 }
 
 export class LiveSyncServiceStub implements ILiveSyncService {
+	public async liveSyncToPreviewApp(data: IPreviewAppLiveSyncData): Promise<IQrCodeImageData> {
+		return;
+	}
+
 	public async liveSync(deviceDescriptors: ILiveSyncDeviceInfo[], liveSyncData: ILiveSyncInfo): Promise<void> {
 		return;
 	}