feat(ios): show the app's forwarded stdout and stderr

Debug builds ask the runtime to forward stdout and stderr through forwardStdio in the app's package.json. They arrive under the org.nativescript.stdio subsystem and show from --log debug, like the rest of the app's native output and as Xcode's console does, labeled with their stream.

Author: rigor789

docs/man_pages/project/testing/run-ios.md

@@ -33,7 +33,7 @@ Start an emulator with specified device identifier and sdk | `$ ns run ios [--de
 * `--emulator` - If set, runs the app in all available and configured ios simulators. It will start a simulator if none are already running.
 * `--sdk` - Specifies the target simulator's sdk.
 * `--justlaunch` - If set, does not print the application output in the console.
-* `--log <Level>` - Also controls how much of the application output is printed. By default only its JavaScript output is shown. `debug` adds everything else the app logs - its native code and the system frameworks it uses, like Xcode's console - and `trace` adds debug level entries as well.
+* `--log <Level>` - Also controls how much of the application output is printed. By default only its JavaScript output is shown. `debug` adds everything else the app logs - its native code, `print()` output and the system frameworks it uses, like Xcode's console - and `trace` adds debug level entries as well.
 * `--clean` - If set, forces the complete rebuild of the native application.
 * `--no-watch` - If set, changes in your code will not be reflected during the execution of this command.
 * `--release` - If set, produces a release build by running webpack in production mode and native build in release mode. Otherwise, produces a debug build.

lib/common/definitions/mobile.d.ts

@@ -173,6 +173,8 @@ declare global {
 			image: string;
 			level: string;
 			message: string;
+			subsystem?: string;
+			category?: string;
 		}
 
 		interface IiOSLogStreamOptions {

lib/common/mobile/ios/ios-log-entry.ts

@@ -38,6 +38,10 @@ export function isIOSRuntimeLogEntry(entry: Mobile.IiOSLogEntry): boolean {
 	return path.basename(entry.image || "") === "NativeScript";
 }
 
+// The runtime forwards the app's stdout and stderr under this subsystem, when
+// the CLI asks for it through the forwardStdio key of the app's package.json.
+const STDIO_SUBSYSTEM = "org.nativescript.stdio";
+
 // Logged by the runtime itself on every launch, not by the app.
 const RUNTIME_NOISE = ["NativeScript loaded bundle"];
 
@@ -57,6 +61,10 @@ export function getIOSLogEntryText(
 		return null;
 	}
 
+	if (entry.subsystem === STDIO_SUBSYSTEM) {
+		return options.includeNative ? `${entry.category}: ${entry.message}` : null;
+	}
+
 	const imageName = path.basename(entry.image || "");
 	if (isIOSRuntimeLogEntry(entry)) {
 		return RUNTIME_NOISE.some((noise) => entry.message.includes(noise))

lib/common/mobile/ios/simulator/ios-simulator-log-provider.ts

@@ -143,6 +143,8 @@ export class IOSSimulatorLogProvider
 				image: event.senderImagePath,
 				level: (event.messageType || "").toLowerCase(),
 				message: event.eventMessage,
+				subsystem: event.subsystem,
+				category: event.category,
 			},
 			this.$devicePlatformsConstants.iOS,
 			deviceId,

lib/common/test/unit-tests/mobile/ios-log-entry.ts

@@ -98,6 +98,47 @@ describe("getIOSLogEntryText", () => {
 	});
 });
 
+describe("getIOSLogEntryText for forwarded stdio", () => {
+	const entry = {
+		process: "/var/containers/Bundle/Application/X/app.app/app",
+		image: "/private/Frameworks/NativeScript.framework/NativeScript",
+		level: "default",
+		message: "printed",
+		subsystem: "org.nativescript.stdio",
+		category: "stdout",
+	};
+
+	it("is hidden by default, unlike the runtime's console output", () => {
+		assert.isNull(getIOSLogEntryText(entry, { processName: "app" }));
+	});
+
+	it("is labeled with its stream along with native output", () => {
+		assert.equal(
+			getIOSLogEntryText(
+				{ ...entry, category: "stderr" },
+				{ processName: "app", includeNative: true },
+			),
+			"stderr: printed",
+		);
+	});
+
+	it("is labeled once when a long line was split", () => {
+		const stitcher = new IOSLogChunkStitcher();
+		const printed: string[] = [];
+		for (const message of ["[ns 4 1/2] one", "[ns 4 2/2]  two"]) {
+			stitcher.add("process", { ...entry, message }, (complete) =>
+				printed.push(
+					getIOSLogEntryText(complete, {
+						processName: "app",
+						includeNative: true,
+					}),
+				),
+			);
+		}
+		assert.deepEqual(printed, ["stdout: one two"]);
+	});
+});
+
 describe("getIOSLogScope", () => {
 	it("maps the CLI log level to the app logs that are shown", () => {
 		assert.deepEqual(getIOSLogScope("INFO", false), {

lib/controllers/prepare-controller.ts

@@ -527,6 +527,7 @@ export class PrepareController
 			}
 			if (prepareData && !prepareData.release) {
 				packageData.logFormat = IOS_LOG_FORMAT;
+				packageData.forwardStdio = true;
 			}
 			if (packageData.ios && packageData.ios.discardUncaughtJsExceptions) {
 				packageData.discardUncaughtJsExceptions =

test/controllers/prepare-controller.ts

@@ -178,9 +178,11 @@ describe("prepareController", () => {
 			return written;
 		};
 
-		it("asks for the structured log format in iOS debug builds only", async () => {
+		it("asks for the structured log format and stdio in iOS debug builds only", async () => {
 			assert.equal((await writePackageJson("ios", false)).logFormat, 1);
 			assert.isUndefined((await writePackageJson("ios", true)).logFormat);
+			assert.isTrue((await writePackageJson("ios", false)).forwardStdio);
+			assert.isUndefined((await writePackageJson("ios", true)).forwardStdio);
 			assert.isUndefined((await writePackageJson("android", false)).logFormat);
 		});
 	});