fix(Server): cascade stats options

lib/Server.js

@@ -72,15 +72,6 @@ if (semver.satisfies(process.version, '8.6.0 - 9')) {
   tls.DEFAULT_ECDH_CURVE = 'auto';
 }
 
-const STATS = {
-  all: false,
-  hash: true,
-  assets: true,
-  warnings: true,
-  errors: true,
-  errorDetails: false,
-};
-
 class Server {
   constructor(compiler, options = {}, _log) {
     this.log = _log || createLogger(options);
@@ -91,6 +82,15 @@ class Server {
       throw new Error("'filename' option must be set in lazy mode.");
     }
 
+    this.stats = options.stats;
+    this.DEFAULT_STATS = {
+      all: false,
+      hash: true,
+      assets: true,
+      warnings: true,
+      errors: true,
+      errorDetails: false,
+    };
     this.hot = options.hot || options.hotOnly;
     this.headers = options.headers;
     this.progress = options.progress;
@@ -144,7 +144,7 @@ class Server {
       compile.tap('webpack-dev-server', invalidPlugin);
       invalid.tap('webpack-dev-server', invalidPlugin);
       done.tap('webpack-dev-server', (stats) => {
-        this._sendStats(this.sockets, stats.toJson(STATS));
+        this._sendStats(this.sockets, this.getStats(stats));
         this._stats = stats;
       });
     };
@@ -650,6 +650,13 @@ class Server {
     }, this);
   }
 
+  getStats(statsObj) {
+    return Object.assign(
+      statsObj.toJson(this.DEFAULT_STATS),
+      statsObj.toJson(this.stats)
+    );
+  }
+
   use() {
     // eslint-disable-next-line
     this.app.use.apply(this.app, arguments);
@@ -817,7 +824,7 @@ class Server {
           return;
         }
 
-        this._sendStats([connection], this._stats.toJson(STATS), true);
+        this._sendStats([connection], this.getStats(this._stats), true);
       });
 
       socket.installHandlers(this.listeningApp, {