[INTERNAL] Add CPU profile generation capability

Can be activated by setting the `UI5LINT_PROFILE` environment variable
to a truthy value.

Based on SAP/ui5-cli#638

Author: RandomByte

packages/ui5-linter/src/cli/base.ts

@@ -95,6 +95,12 @@ async function handleLint(argv: yargs.ArgumentsCamelCase) {
 		format
 	} = <{ coverage: boolean, filePaths: string[], details: boolean, format: string }><unknown>argv;
 
+	let profile;
+	if (process.env.UI5LINT_PROFILE) {
+		profile = await import("./utils/profile.js");
+		await profile.start();
+	}
+
 	const res = await lintProject({
 		rootDir: path.join(process.cwd()),
 		filePaths: filePaths && filePaths.map((filePath) => path.resolve(process.cwd(), filePath)),
@@ -113,7 +119,10 @@ async function handleLint(argv: yargs.ArgumentsCamelCase) {
 		const textFormatter = new Text();
 		process.stderr.write(textFormatter.format(res, details));
 	}
-
+	// Stop profiling after CLI finished execution
+	if (profile) {
+		await profile.stop();
+	}
 }
 
 export default function base(cli: yargs.Argv) {

packages/ui5-linter/src/cli/utils/profile.ts

@@ -0,0 +1,98 @@
+import {writeFile} from "node:fs/promises";
+import {Session, Profiler} from "node:inspector";
+import {getLogger} from "@ui5/logger";
+const log = getLogger("cli:utils:profile");
+
+let session: Session | null;
+type ProcessSignals = Record<string, (exitCode: number) => void>
+let processSignals: ProcessSignals | null;
+
+export async function start() {
+	if (session) {
+		return;
+	}
+	session = new Session();
+	session.connect();
+	await new Promise<void>((resolve) => {
+		session?.post("Profiler.enable", () => {
+			log.info(`Recording CPU profile...`);
+			session?.post("Profiler.start", () => {
+				processSignals = registerSigHooks();
+				resolve();
+			});
+		});
+	});
+}
+
+async function writeProfile(profile: Profiler.Profile) {
+	const formatter = new Intl.DateTimeFormat("en-GB", {
+		year: "numeric",
+		month: "2-digit",
+		day: "2-digit",
+		hour: "2-digit",
+		minute: "2-digit",
+		second: "2-digit",
+	});
+	const dateParts = Object.create(null);
+	const parts = formatter.formatToParts(new Date());
+	parts.forEach((p) => {
+		dateParts[p.type] = p.value;
+	});
+
+	const fileName = `./ui5_${dateParts.year}-${dateParts.month}-${dateParts.day}_` +
+		`${dateParts.hour}-${dateParts.minute}-${dateParts.second}.cpuprofile`;
+	log.info(`\nSaving CPU profile to ${fileName}...`);
+	await writeFile(fileName, JSON.stringify(profile));
+}
+
+export async function stop() {
+	if (!session) {
+		return;
+	}
+	if (processSignals) {
+		deregisterSigHooks(processSignals);
+		processSignals = null;
+	}
+	const profile = await new Promise<Profiler.Profile | null>((resolve) => {
+		session?.post("Profiler.stop", (err, {profile}) => {
+			if (err) {
+				resolve(null);
+			} else {
+				resolve(profile);
+			}
+		});
+		session = null;
+	});
+	if (profile) {
+		await writeProfile(profile);
+	}
+}
+
+function registerSigHooks() {
+	function createListener(exitCode: number) {
+		return function() {
+			// Gracefully end profiling, then exit
+			stop().then(() => {
+				process.exit(exitCode);
+			});
+		};
+	}
+
+	const processSignals: ProcessSignals = {
+		"SIGHUP": createListener(128 + 1),
+		"SIGINT": createListener(128 + 2),
+		"SIGTERM": createListener(128 + 15),
+		"SIGBREAK": createListener(128 + 21)
+	};
+
+	for (const signal of Object.keys(processSignals)) {
+		process.on(signal, processSignals[signal]);
+	}
+	return processSignals;
+}
+
+function deregisterSigHooks(signals: ProcessSignals) {
+	for (const signal of Object.keys(signals)) {
+		process.removeListener(signal, signals[signal]);
+	}
+}