fix: preview and run do not work correctly

In case there are multiple devices with the same platform, `run command` fails with error `Cannot read property hasNativeChanges of undefined`. The problem is that we return incorrect prepare data.
Also we have a problem in `tns preview` when multiple platforms are used - all files are send multiple times to each device as we have too many started webpack processes (in case you scan fast with devices) and we are also adding handler of the prepare ready event per each device instead per platform. Fix this by handling the event only once per platform

Author: rosen-vladimirov

lib/controllers/prepare-controller.ts

@@ -1,4 +1,3 @@
-import * as child_process from "child_process";
 import * as choki from "chokidar";
 import { hook } from "../common/helpers";
 import { performanceLog } from "../common/decorators";
@@ -7,7 +6,7 @@ import * as path from "path";
 import { PREPARE_READY_EVENT_NAME, WEBPACK_COMPILATION_COMPLETE, PACKAGE_JSON_FILE_NAME, PLATFORMS_DIR_NAME } from "../constants";
 
 interface IPlatformWatcherData {
-	webpackCompilerProcess: child_process.ChildProcess;
+	hasWebpackCompilerProcess: boolean;
 	nativeFilesWatcher: choki.FSWatcher;
 }
 
@@ -63,9 +62,9 @@ export class PrepareController extends EventEmitter {
 			this.watchersData[projectDir][platformLowerCase].nativeFilesWatcher = null;
 		}
 
-		if (this.watchersData && this.watchersData[projectDir] && this.watchersData[projectDir][platformLowerCase] && this.watchersData[projectDir][platformLowerCase].webpackCompilerProcess) {
+		if (this.watchersData && this.watchersData[projectDir] && this.watchersData[projectDir][platformLowerCase] && this.watchersData[projectDir][platformLowerCase].hasWebpackCompilerProcess) {
 			await this.$webpackCompilerService.stopWebpackCompiler(platform);
-			this.watchersData[projectDir][platformLowerCase].webpackCompilerProcess = null;
+			this.watchersData[projectDir][platformLowerCase].hasWebpackCompilerProcess = false;
 		}
 	}
 
@@ -78,38 +77,39 @@ export class PrepareController extends EventEmitter {
 		if (!this.watchersData[projectData.projectDir][platformData.platformNameLowerCase]) {
 			this.watchersData[projectData.projectDir][platformData.platformNameLowerCase] = {
 				nativeFilesWatcher: null,
-				webpackCompilerProcess: null
+				hasWebpackCompilerProcess: false
 			};
-			await this.startJSWatcherWithPrepare(platformData, projectData, prepareData); // -> start watcher + initial compilation
-			const hasNativeChanges = await this.startNativeWatcherWithPrepare(platformData, projectData, prepareData); // -> start watcher + initial prepare
-			const result = { platform: platformData.platformNameLowerCase, hasNativeChanges };
+		}
 
-			const hasPersistedDataWithNativeChanges = this.persistedData.find(data => data.platform === result.platform && data.hasNativeChanges);
-			if (hasPersistedDataWithNativeChanges) {
-				result.hasNativeChanges = true;
-			}
+		await this.startJSWatcherWithPrepare(platformData, projectData, prepareData); // -> start watcher + initial compilation
+		const hasNativeChanges = await this.startNativeWatcherWithPrepare(platformData, projectData, prepareData); // -> start watcher + initial prepare
+		const result = { platform: platformData.platformNameLowerCase, hasNativeChanges };
 
-			// TODO: Do not persist this in `this` context. Also it should be per platform.
-			this.isInitialPrepareReady = true;
+		const hasPersistedDataWithNativeChanges = this.persistedData.find(data => data.platform === result.platform && data.hasNativeChanges);
+		if (hasPersistedDataWithNativeChanges) {
+			result.hasNativeChanges = true;
+		}
 
-			if (this.persistedData && this.persistedData.length) {
-				this.emitPrepareEvent({ files: [], hasOnlyHotUpdateFiles: false, hasNativeChanges: result.hasNativeChanges, hmrData: null, platform: platformData.platformNameLowerCase });
-			}
+		// TODO: Do not persist this in `this` context. Also it should be per platform.
+		this.isInitialPrepareReady = true;
 
-			return result;
+		if (this.persistedData && this.persistedData.length) {
+			this.emitPrepareEvent({ files: [], hasOnlyHotUpdateFiles: false, hasNativeChanges: result.hasNativeChanges, hmrData: null, platform: platformData.platformNameLowerCase });
 		}
+
+		return result;
 	}
 
 	private async startJSWatcherWithPrepare(platformData: IPlatformData, projectData: IProjectData, prepareData: IPrepareData): Promise<void> {
-		if (!this.watchersData[projectData.projectDir][platformData.platformNameLowerCase].webpackCompilerProcess) {
+		if (!this.watchersData[projectData.projectDir][platformData.platformNameLowerCase].hasWebpackCompilerProcess) {
 			this.$webpackCompilerService.on(WEBPACK_COMPILATION_COMPLETE, data => {
 				if (data.platform.toLowerCase() === platformData.platformNameLowerCase) {
 					this.emitPrepareEvent({ ...data, hasNativeChanges: false });
 				}
 			});
 
-			const childProcess = await this.$webpackCompilerService.compileWithWatch(platformData, projectData, prepareData);
-			this.watchersData[projectData.projectDir][platformData.platformNameLowerCase].webpackCompilerProcess = childProcess;
+			this.watchersData[projectData.projectDir][platformData.platformNameLowerCase].hasWebpackCompilerProcess = true;
+			await this.$webpackCompilerService.compileWithWatch(platformData, projectData, prepareData);
 		}
 	}
 

lib/controllers/preview-app-controller.ts

@@ -79,8 +79,10 @@ export class PreviewAppController extends EventEmitter implements IPreviewAppCon
 					this.platformPrepareHandlers[device.platform] = true;
 
 					// TODO: Remove the handler once the preview operation for this platform is stopped
-					this.$prepareController.on(PREPARE_READY_EVENT_NAME, async currentPrepareData => {
-						await this.handlePrepareReadyEvent(data, currentPrepareData.hmrData, currentPrepareData.files, device.platform);
+					this.$prepareController.on(PREPARE_READY_EVENT_NAME, async (currentPrepareData: IFilesChangeEventData) => {
+						if (currentPrepareData.platform.toLowerCase() === device.platform.toLowerCase()) {
+							await this.handlePrepareReadyEvent(data, currentPrepareData.hmrData, currentPrepareData.files, device.platform);
+						}
 					});
 
 				}