use memfs instead of memory-fs

lib/fs.js

@@ -2,13 +2,17 @@
 
 const fs = require('fs');
 const path = require('path');
-const MemoryFileSystem = require('memory-fs');
+const { fs: memfs } = require('memfs');
+// borrow join and normalize from memory-fs
+memfs.join = require('memory-fs/lib/join');
+memfs.normalize = require('memory-fs/lib/normalize');
 const { colors } = require('webpack-log');
 const NodeOutputFileSystem = require('webpack/lib/node/NodeOutputFileSystem');
 const DevMiddlewareError = require('./DevMiddlewareError');
 
 const { mkdirp } = new NodeOutputFileSystem();
 
+
 module.exports = {
   toDisk(context) {
     const compilers = context.compiler.compilers || [context.compiler];
@@ -60,12 +64,12 @@ module.exports = {
 
     let fileSystem;
     // store our files in memory
-    const isMemoryFs = !compiler.compilers && compiler.outputFileSystem instanceof MemoryFileSystem;
+    const isMemoryFs = !compiler.compilers && compiler.outputFileSystem === memfs;
 
     if (isMemoryFs) {
       fileSystem = compiler.outputFileSystem;
     } else {
-      fileSystem = new MemoryFileSystem();
+      fileSystem = memfs;
       compiler.outputFileSystem = fileSystem;
     }
 

package.json

@@ -16,6 +16,7 @@
     "release": "standard-version"
   },
   "dependencies": {
+    "memfs": "^2.15.0",
     "memory-fs": "~0.4.1",
     "mime": "^2.3.1",
     "range-parser": "^1.0.3",

test/tests/server.js

@@ -22,7 +22,7 @@ describe('Server', () => {
   const logLevel = 'error';
 
   function listenShorthand(done) {
-    return app.listen(8000, '127.0.0.1', (err) => {
+    return app.listen(3000, '127.0.0.1', (err) => {
       if (err) done(err);
       done();
     });
@@ -390,7 +390,7 @@ describe('Server', () => {
     });
 
     it('request to non-public path', (done) => {
-      request(app).get('/').expect(404, done);
+      request(app).get('/nonpublic/').expect(404, done);
     });
   });