Replace express with builtin node server

Alternative to long-standing webpack-contrib#212

Express in this project does not add much value. Middleware api is not
necessary for 1.5 middlwares. We can try to use node server directly.

Serving static is left for express middleware. Can be replaced with
something smaller in another PR.

package.json

@@ -39,11 +39,11 @@
     "chalk": "^4.1.0",
     "commander": "^6.2.0",
     "ejs": "^3.1.5",
-    "express": "^4.17.1",
     "filesize": "^6.1.0",
     "gzip-size": "^6.0.0",
     "lodash": "^4.17.20",
     "opener": "^1.5.2",
+    "serve-static": "^1.14.1",
     "ws": "^7.3.1"
   },
   "devDependencies": {

src/viewer.js

@@ -4,7 +4,7 @@ const http = require('http');
 
 const WebSocket = require('ws');
 const _ = require('lodash');
-const express = require('express');
+const serveStatic = require('serve-static');
 const ejs = require('ejs');
 const {bold} = require('chalk');
 
@@ -14,6 +14,7 @@ const {open} = require('./utils');
 
 const projectRoot = path.resolve(__dirname, '..');
 const assetsRoot = path.join(projectRoot, 'public');
+const viewsRoot = path.join(projectRoot, 'views');
 
 function resolveTitle(reportTitle) {
   if (typeof reportTitle === 'function') {
@@ -49,28 +50,44 @@ async function startServer(bundleStats, opts) {
 
   if (!chartData) return;
 
-  const app = express();
-
-  // Explicitly using our `ejs` dependency to render templates
-  // Fixes #17
-  app.engine('ejs', require('ejs').renderFile);
-  app.set('view engine', 'ejs');
-  app.set('views', `${projectRoot}/views`);
-  app.use(express.static(`${projectRoot}/public`));
-
-  app.use('/', (req, res) => {
-    res.render('viewer', {
-      mode: 'server',
-      title: resolveTitle(reportTitle),
-      get chartData() { return chartData },
-      defaultSizes,
-      enableWebSocket: true,
-      // Helpers
-      escapeJson
-    });
-  });
+  const serveStaticMiddleware = serveStatic(`${projectRoot}/public`);
+
+  const handleError = (res, err) => {
+    console.error(err.stack || err.toString());
+    res.writeHead(500);
+    res.end();
+  };
 
-  const server = http.createServer(app);
+  const server = http.createServer((req, res) => {
+    if (req.method === 'GET' && req.url === '/') {
+      const data = {
+        mode: 'server',
+        title: resolveTitle(reportTitle),
+        get chartData() { return chartData },
+        defaultSizes,
+        enableWebSocket: true,
+        // Helpers
+        escapeJson
+      };
+      ejs.renderFile(`${viewsRoot}/viewer.ejs`, data, {cache: true}, (err, html) => {
+        if (err) {
+          handleError(res, err);
+        } else {
+          res.writeHead(200, {'Content-Type': 'text/html'});
+          return res.end(html);
+        }
+      });
+    } else {
+      serveStaticMiddleware(req, res, err => {
+        if (err) {
+          handleError(res, err);
+        } else {
+          res.writeHead(404);
+          res.end();
+        }
+      });
+    }
+  });
 
   await new Promise(resolve => {
     server.listen(port, host, () => {