refactor: centralize server port resolution (#4198)

I took a look at the last remaining FIXME comment in the code - the one
in `js/app.js` pointing to PR #673. It's from 2017 and was already
flagged as a hotfix back then.

The problem: `MM_PORT` got written into a global `global.mmPort` that
was then read inconsistently across the code - sometimes via the global,
sometimes straight from `process.env`, plus separate logic in
`defaults.js`. Three ways to get the same port.

I pulled this into a single `getServerPort()` helper (`MM_PORT` ->
`config.port` -> `8080`) and switched `app.js`, `defaults.js`,
`server.js`, `electron.js` and both serveronly files over to it. The
global is gone now.

Basically the behavior should be unchanged.

js/app.js

@@ -42,12 +42,6 @@ if (process.env.MM_CONFIG_FILE) {
 	global.configuration_file = process.env.MM_CONFIG_FILE.replace(`${global.root_path}/`, "");
 }
 
-// FIXME: Hotfix Pull Request
-// https://github.com/MagicMirrorOrg/MagicMirror/pull/673
-if (process.env.MM_PORT) {
-	global.mmPort = process.env.MM_PORT;
-}
-
 // The next part is here to prevent a major exception when there
 // is no internet connection. This could probable be solved better.
 process.on("uncaughtException", function (err) {

js/defaults.js

@@ -1,13 +1,6 @@
-/* global mmPort */
-
-const address = "localhost";
-let port = 8080;
-if (typeof mmPort !== "undefined") {
-	port = mmPort;
-}
 const defaults = {
-	address: address,
-	port: port,
+	address: "localhost",
+	port: 8080,
 	basePath: "/",
 	useHttps: false, // Support HTTPS or not, default "false" will use HTTP
 	httpsPrivateKey: "", // HTTPS private key path, only required when useHttps is true

js/electron.js

@@ -4,6 +4,7 @@ const electron = require("electron");
 const core = require("./app");
 const Log = require("./logger");
 const { applyElectronSwitches } = require("./electron_helper");
+const { getServerPort } = require("#server_functions");
 
 // Config
 let config = process.env.config ? JSON.parse(process.env.config) : {};
@@ -101,7 +102,7 @@ function createWindow () {
 	}
 
 	const address = (config.address === void 0) | (config.address === "") | (config.address === "0.0.0.0") | (config.address === "::") ? (config.address = "localhost") : config.address;
-	const port = process.env.MM_PORT || config.port;
+	const port = getServerPort(config);
 	mainWindow.loadURL(`${prefix}${address}:${port}`);
 
 	// Open the DevTools if run with "node --run start:dev"

js/server.js

@@ -11,7 +11,7 @@ const { ipAccessControl, socketIpAccessControl } = require("./ip_access_control"
 
 const vendor = require("./vendor");
 
-const { getHtml, getVersion, getEnvVars, cors } = require("#server_functions");
+const { getHtml, getVersion, getEnvVars, getServerPort, cors } = require("#server_functions");
 
 /**
  * Server
@@ -21,7 +21,7 @@ const { getHtml, getVersion, getEnvVars, cors } = require("#server_functions");
 function Server (configObj) {
 	const config = configObj.fullConf;
 	const app = express();
-	const port = process.env.MM_PORT || config.port;
+	const port = getServerPort(config);
 	const serverSockets = new Set();
 	let server = null;
 

js/server_functions.js

@@ -251,6 +251,16 @@ function getEnvVars (req, res) {
 	res.send(obj);
 }
 
+/**
+ * Resolves the HTTP server port. The `MM_PORT` environment variable takes
+ * precedence over the configured port, falling back to 8080.
+ * @param {object} [config] the configuration to read the port from (defaults to global.config)
+ * @returns {number} the port the server should listen on
+ */
+function getServerPort (config = global.config) {
+	return Number(process.env.MM_PORT || config?.port || 8080);
+}
+
 /**
  * Get the config file path from environment or default location
  * @returns {string} The absolute config file path
@@ -269,4 +279,4 @@ function getConfigFilePath () {
 	return path.resolve(global.configuration_file || `${global.root_path}/config/config.js`);
 }
 
-module.exports = { cors, getHtml, getVersion, getStartup, getEnvVars, getEnvVarsAsObj, getUserAgent, getConfigFilePath, replaceSecretPlaceholder };
+module.exports = { cors, getHtml, getVersion, getStartup, getEnvVars, getEnvVarsAsObj, getUserAgent, getServerPort, getConfigFilePath, replaceSecretPlaceholder };

serveronly/index.js

@@ -1,8 +1,9 @@
 const app = require("../js/app");
 const Log = require("../js/logger");
+const { getServerPort } = require("#server_functions");
 
 app.start().then((config) => {
 	const bindAddress = config.address ? config.address : "localhost";
 	const httpType = config.useHttps ? "https" : "http";
-	Log.info(`\n>>>   Ready to go! Please point your browser to: ${httpType}://${bindAddress}:${global.mmPort || config.port}   <<<`);
+	Log.info(`\n>>>   Ready to go! Please point your browser to: ${httpType}://${bindAddress}:${getServerPort(config)}   <<<`);
 });

serveronly/watcher.js

@@ -7,7 +7,7 @@ const path = require("node:path");
 const net = require("node:net");
 const http = require("node:http");
 const Log = require("logger");
-const { getConfigFilePath } = require("#server_functions");
+const { getConfigFilePath, getServerPort } = require("#server_functions");
 
 const RESTART_DELAY_MS = 500;
 const PORT_CHECK_MAX_ATTEMPTS = 20;
@@ -32,7 +32,7 @@ function getServerConfig () {
 		delete require.cache[require.resolve(configPath)];
 		const config = require(configPath);
 		serverConfig = {
-			port: global.mmPort || config.port || 8080,
+			port: getServerPort(config),
 			address: config.address || "localhost"
 		};
 	} catch {