fix: memory leak when writeToDisk used (#472)

Author: evilebottnawi

lib/fs.js

@@ -15,6 +15,10 @@ module.exports = {
 
     for (const compiler of compilers) {
       compiler.hooks.emit.tap('WebpackDevMiddleware', (compilation) => {
+        if (compiler.hasWebpackDevMiddlewareAssetEmittedCallback) {
+          return;
+        }
+
         compiler.hooks.assetEmitted.tapAsync(
           'WebpackDevMiddleware',
           (file, content, callback) => {
@@ -74,6 +78,7 @@ module.exports = {
             });
           }
         );
+        compiler.hasWebpackDevMiddlewareAssetEmittedCallback = true;
       });
     }
   },