[core] refactor: enable ESLint rule require-await and handle detected issues (#4038)

Enable the `require-await` ESLint rule. Async functions without `await`
are just regular functions with extra overhead — marking them `async`
adds implicit Promise wrapping, can hide missing `return` statements,
and misleads readers into expecting asynchronous behavior where there is
none.

While fixing the violations, I removed unnecessary `async` keywords from
source files and from various test callbacks that never used `await`.

defaultmodules/weather/providers/envcanada.js

@@ -31,7 +31,7 @@ class EnvCanadaProvider {
 		this.currentHour = null; // Track current hour for URL updates
 	}
 
-	async initialize () {
+	initialize () {
 		this.#validateConfig();
 		this.#initializeFetcher();
 	}

defaultmodules/weather/providers/openweathermap.js

@@ -28,7 +28,7 @@ class OpenWeatherMapProvider {
 		this.locationName = null;
 	}
 
-	async initialize () {
+	initialize () {
 		// Validate callbacks exist
 		if (typeof this.onErrorCallback !== "function") {
 			throw new Error("setCallbacks() must be called before initialize()");

defaultmodules/weather/providers/pirateweather.js

@@ -24,7 +24,7 @@ class PirateweatherProvider {
 		this.onErrorCallback = onErrorCallback;
 	}
 
-	async initialize () {
+	initialize () {
 		if (!this.config.apiKey) {
 			Log.error("[pirateweather] No API key configured");
 			if (this.onErrorCallback) {

defaultmodules/weather/providers/smhi.js

@@ -29,7 +29,7 @@ class SMHIProvider {
 		this.onErrorCallback = null;
 	}
 
-	async initialize () {
+	initialize () {
 		try {
 			// SMHI requires max 6 decimal places
 			validateCoordinates(this.config, 6);

defaultmodules/weather/providers/ukmetofficedatahub.js

@@ -35,7 +35,7 @@ class UkMetOfficeDataHubProvider {
 		this.onErrorCallback = onErrorCallback;
 	}
 
-	async initialize () {
+	initialize () {
 		if (!this.config.apiKey || this.config.apiKey === "YOUR_API_KEY_HERE") {
 			Log.error("[ukmetofficedatahub] No API key configured");
 			if (this.onErrorCallback) {

defaultmodules/weather/providers/weatherapi.js

@@ -25,7 +25,7 @@ class WeatherAPIProvider {
 		this.onErrorCallback = null;
 	}
 
-	async initialize () {
+	initialize () {
 		this.#validateConfig();
 		this.#initializeFetcher();
 	}

defaultmodules/weather/providers/weatherbit.js

@@ -27,7 +27,7 @@ class WeatherbitProvider {
 		this.onErrorCallback = onErrorCallback;
 	}
 
-	async initialize () {
+	initialize () {
 		if (!this.config.apiKey || this.config.apiKey === "YOUR_API_KEY_HERE") {
 			Log.error("[weatherbit] No API key configured");
 			if (this.onErrorCallback) {

defaultmodules/weather/providers/weatherflow.js

@@ -31,7 +31,7 @@ class WeatherFlowProvider {
 	/**
 	 * Initialize the provider
 	 */
-	async initialize () {
+	initialize () {
 		if (!this.config.token || this.config.token === "YOUR_API_TOKEN_HERE") {
 			Log.error("[weatherflow] No API token configured. Get one at https://tempestwx.com/");
 			if (this.onErrorCallback) {

eslint.config.mjs

@@ -75,6 +75,7 @@ export default defineConfig([
 			"object-shorthand": ["error", "methods"],
 			"one-var": "off",
 			"prefer-template": "error",
+			"require-await": "error",
 			"sort-keys": "off"
 		}
 	},

js/loader.js

@@ -193,7 +193,7 @@ const Loader = (function () {
 	 * @param {string} fileName Path of the file we want to load.
 	 * @returns {Promise} resolved when the file is loaded
 	 */
-	const loadFile = async function (fileName) {
+	const loadFile = function (fileName) {
 		const extension = fileName.slice((Math.max(0, fileName.lastIndexOf(".")) || Infinity) + 1);
 		let script, stylesheet;
 
@@ -267,10 +267,10 @@ const Loader = (function () {
 		 * @param {Module} module The module that calls the loadFile function.
 		 * @returns {Promise} resolved when the file is loaded
 		 */
-		async loadFileForModule (fileName, module) {
+		loadFileForModule (fileName, module) {
 			if (loadedFiles.indexOf(fileName.toLowerCase()) !== -1) {
 				Log.log(`File already loaded: ${fileName}`);
-				return;
+				return Promise.resolve();
 			}
 
 			if (fileName.indexOf("http://") === 0 || fileName.indexOf("https://") === 0 || fileName.indexOf("/") !== -1) {

js/module.js

@@ -43,7 +43,7 @@ const Module = Class.extend({
 	/**
 	 * Called when the module is started.
 	 */
-	async start () {
+	start () {
 		Log.info(`Starting module: ${this.name}`);
 	},
 

serveronly/watcher.js

@@ -145,10 +145,10 @@ function notifyClientsToReload () {
  * Restart the server process
  * @param {string} reason The reason for the restart
  */
-async function restartServer (reason) {
+function restartServer (reason) {
 	if (restartTimer) clearTimeout(restartTimer);
 
-	restartTimer = setTimeout(async () => {
+	restartTimer = setTimeout(() => {
 		Log.info(reason);
 
 		if (child) {

tests/e2e/clientonly_spec.js

@@ -133,7 +133,7 @@ describe("Clientonly parameter handling", () => {
 	});
 
 	describe("Display environment check", () => {
-		it("should fail without DISPLAY or WAYLAND_DISPLAY when connecting to valid server", async () => {
+		it("should fail without DISPLAY or WAYLAND_DISPLAY when connecting to valid server", () => {
 			// This test needs a running server to get past the connection phase
 			// Without DISPLAY, it should fail with display error
 			// For now, we just verify it fails (connection error comes first without server)
@@ -159,7 +159,7 @@ describe("Clientonly with running server", () => {
 		await delay(2000);
 	});
 
-	afterAll(async () => {
+	afterAll(() => {
 		if (serverProcess && serverProcess.pid) {
 			try {
 				process.kill(-serverProcess.pid);

tests/e2e/config_variables_spec.js

@@ -9,19 +9,19 @@ describe("config with variables and secrets", () => {
 		await helpers.stopApplication();
 	});
 
-	it("config.language should be \"de\"", async () => {
+	it("config.language should be \"de\"", () => {
 		expect(config.language).toBe("de");
 	});
 
-	it("config.loglevel should be [\"ERROR\", \"LOG\", \"WARN\", \"INFO\"]", async () => {
+	it("config.loglevel should be [\"ERROR\", \"LOG\", \"WARN\", \"INFO\"]", () => {
 		expect(config.logLevel).toStrictEqual(["ERROR", "LOG", "WARN", "INFO"]);
 	});
 
-	it("config.ipWhitelist should be [\"::ffff:127.0.0.1\", \"::1\", \"127.0.0.1\"]", async () => {
+	it("config.ipWhitelist should be [\"::ffff:127.0.0.1\", \"::1\", \"127.0.0.1\"]", () => {
 		expect(config.ipWhitelist).toStrictEqual(["::ffff:127.0.0.1", "::1", "127.0.0.1"]);
 	});
 
-	it("config.timeFormat should be 12", async () => {
+	it("config.timeFormat should be 12", () => {
 		expect(config.timeFormat).toBe(12); // default is 24
 	});
 

tests/e2e/modules/newsfeed_spec.js

@@ -2,7 +2,7 @@ const fs = require("node:fs");
 const { expect } = require("playwright/test");
 const helpers = require("../helpers/global-setup");
 
-const runTests = async () => {
+const runTests = () => {
 	let page;
 
 	describe("Default configuration", () => {

tests/unit/classes/translator_spec.js

@@ -93,7 +93,7 @@ describe("Translator", () => {
 			Translator.coreTranslationsFallback = coreTranslationsFallback;
 		};
 
-		it("should return custom module translation", async () => {
+		it("should return custom module translation", () => {
 			const { Translator } = createTranslationTestEnvironment();
 			setTranslations(Translator);
 
@@ -104,7 +104,7 @@ describe("Translator", () => {
 			expect(translation).toBe("Hallo fewieden");
 		});
 
-		it("should return core translation", async () => {
+		it("should return core translation", () => {
 			const { Translator } = createTranslationTestEnvironment();
 			setTranslations(Translator);
 			let translation = Translator.translate({ name: "MMM-Module" }, "FOO");
@@ -113,28 +113,28 @@ describe("Translator", () => {
 			expect(translation).toBe("Bar Lorem Ipsum");
 		});
 
-		it("should return custom module translation fallback", async () => {
+		it("should return custom module translation fallback", () => {
 			const { Translator } = createTranslationTestEnvironment();
 			setTranslations(Translator);
 			const translation = Translator.translate({ name: "MMM-Module" }, "A key");
 			expect(translation).toBe("A translation");
 		});
 
-		it("should return core translation fallback", async () => {
+		it("should return core translation fallback", () => {
 			const { Translator } = createTranslationTestEnvironment();
 			setTranslations(Translator);
 			const translation = Translator.translate({ name: "MMM-Module" }, "Fallback");
 			expect(translation).toBe("core fallback");
 		});
 
-		it("should return translation with placeholder for missing variables", async () => {
+		it("should return translation with placeholder for missing variables", () => {
 			const { Translator } = createTranslationTestEnvironment();
 			setTranslations(Translator);
 			const translation = Translator.translate({ name: "MMM-Module" }, "Hello {username}");
 			expect(translation).toBe("Hallo {username}");
 		});
 
-		it("should return key if no translation was found", async () => {
+		it("should return key if no translation was found", () => {
 			const { Translator } = createTranslationTestEnvironment();
 			setTranslations(Translator);
 			const translation = Translator.translate({ name: "MMM-Module" }, "MISSING");

tests/unit/functions/server_functions_spec.js

@@ -163,7 +163,7 @@ describe("server_functions tests", () => {
 			expect(corsResponse.set.mock.calls[2][1]).toBe("value2");
 		});
 
-		it("Gets User-Agent from configuration", async () => {
+		it("Gets User-Agent from configuration", () => {
 			const previousConfig = global.config;
 			global.config = {};
 			let userAgent;

tests/unit/functions/updatenotification_spec.js

@@ -320,7 +320,7 @@ describe("Updatenotification", () => {
 	describe("custom module", () => {
 		const moduleName = "MMM-Fuel";
 
-		beforeEach(async () => {
+		beforeEach(() => {
 			gitRemoteOut = `origin\thttps://github.com/fewieden/${moduleName}.git (fetch)\norigin\thttps://github.com/fewieden/${moduleName}.git (push)\n`;
 			gitRevParseOut = "9d8310163da94441073a93cead711ba43e8888d0";
 			gitStatusOut = "## master...origin/master";

tests/unit/helpers/global-setup.js

@@ -1,3 +1,3 @@
-module.exports = async () => {
+module.exports = () => {
 	process.env.TZ = "UTC";
 };

tests/unit/modules/default/utils_spec.js

@@ -7,7 +7,7 @@ describe("Default modules utils tests", () => {
 	describe("formatTime", () => {
 		const time = new Date();
 
-		beforeEach(async () => {
+		beforeEach(() => {
 			time.setHours(13, 13);
 		});
 

tests/unit/modules/default/weather/providers/envcanada_spec.js

@@ -67,10 +67,10 @@ describe("EnvCanadaProvider", () => {
 			expect(provider.config.type).toBe("current");
 		});
 
-		it("should throw error if siteCode or provCode missing", async () => {
+		it("should throw error if siteCode or provCode missing", () => {
 			const provider = new EnvCanadaProvider({ siteCode: "", provCode: "" });
 			provider.setCallbacks(vi.fn(), vi.fn());
-			await expect(provider.initialize()).rejects.toThrow("siteCode and provCode are required");
+			expect(() => provider.initialize()).toThrow("siteCode and provCode are required");
 		});
 	});
 

tests/unit/modules/default/weather/providers/openweathermap_spec.js

@@ -70,9 +70,9 @@ describe("OpenWeatherMapProvider", () => {
 			expect(provider.fetcher).toBeNull();
 		});
 
-		it("should throw if setCallbacks not called before initialize", async () => {
+		it("should throw if setCallbacks not called before initialize", () => {
 			const provider = new OpenWeatherMapProvider({ apiKey: "test" });
-			await expect(provider.initialize()).rejects.toThrow("setCallbacks");
+			expect(() => provider.initialize()).toThrow("setCallbacks");
 		});
 	});