fix(ios): launch the app once when restarting it on a device

restartApplication launched the app and then connected to its debug socket with ensureAppStarted, which launched it again with --terminate-existing and killed the first process. The socket now connects to the running instance. A launch waiting for a debugger keeps the second start, since that instance cannot answer the attach request.

Author: rigor789

lib/services/livesync/ios-device-livesync-service.ts

@@ -58,7 +58,8 @@ export class IOSDeviceLiveSyncService
 	}
 
 	private async setupSocketIfNeeded(
-		projectData: IProjectData
+		projectData: IProjectData,
+		ensureAppStarted: boolean = true
 	): Promise<boolean> {
 		// TODO: persist the sockets per app in order to support LiveSync on multiple apps on the same device
 		if (this.socket) {
@@ -67,8 +68,6 @@ export class IOSDeviceLiveSyncService
 
 		const appId = projectData.projectIdentifiers.ios;
 		try {
-			// TODO: temp workaround till we setup the sockets along with the app start
-			const ensureAppStarted = true;
 			this.socket = await this.device.getDebugSocket(
 				appId,
 				projectData.projectName,
@@ -217,7 +216,13 @@ export class IOSDeviceLiveSyncService
 
 		if (liveSyncInfo.useHotModuleReload) {
 			// enable HOT updates
-			await this.setupSocketIfNeeded(projectData);
+			// Starting the app again here would terminate the instance launched
+			// above. Only a launch that waits for a debugger still needs it, as
+			// that instance cannot answer the attach request.
+			await this.setupSocketIfNeeded(
+				projectData,
+				!!liveSyncInfo.waitForDebugger
+			);
 		}
 	}
 

test/services/livesync/ios-device-livesync-service.ts

@@ -0,0 +1,62 @@
+import * as assert from "assert";
+import { IOSDeviceLiveSyncService } from "../../../lib/services/livesync/ios-device-livesync-service";
+
+describe("IOSDeviceLiveSyncService", () => {
+	const projectData: any = {
+		projectName: "app",
+		projectDir: "/app",
+		projectIdentifiers: { ios: "org.app" },
+	};
+
+	const restart = async (waitForDebugger: boolean) => {
+		const calls: string[] = [];
+		const ensureAppStartedValues: boolean[] = [];
+		const device: any = {
+			applicationManager: {
+				restartApplication: async () => {
+					calls.push("restart");
+				},
+			},
+			getDebugSocket: async (
+				_appId: string,
+				_projectName: string,
+				_projectDir: string,
+				ensureAppStarted: boolean
+			) => {
+				calls.push("socket");
+				ensureAppStartedValues.push(ensureAppStarted);
+				return { on: () => {}, removeAllListeners: () => {} };
+			},
+		};
+		const service = new (<any>IOSDeviceLiveSyncService)(
+			{ trace: () => {} },
+			{},
+			{},
+			{},
+			{},
+			{},
+			device
+		);
+
+		await service.restartApplication(projectData, {
+			deviceAppData: { appIdentifier: "org.app" },
+			useHotModuleReload: true,
+			waitForDebugger,
+		});
+
+		return { calls, ensureAppStartedValues };
+	};
+
+	it("connects to the app it restarted without starting it again", async () => {
+		const { calls, ensureAppStartedValues } = await restart(false);
+
+		assert.deepStrictEqual(calls, ["restart", "socket"]);
+		assert.deepStrictEqual(ensureAppStartedValues, [false]);
+	});
+
+	it("starts the app again when the restarted instance waits for a debugger", async () => {
+		const { ensureAppStartedValues } = await restart(true);
+
+		assert.deepStrictEqual(ensureAppStartedValues, [true]);
+	});
+});