Latest memfs version breaks serve from memory - Cannot GET /

[Mirrrek]

Bug report

Yesterday, streamich/memfs version 4.43.0 was released (dependency of webpack-dev-middleware), which breaks serving files from memory (only files in the devServer.static folder are served).

I did not dig deeper into the bug, it is possible that this is caused by an incorrect configuration on my end, but it happened to me on a fresh webpack project with the latest packages.

Actual Behavior

When launching webpack serve --mode development with the webpack.config.js below (on webpack@5.101.3, webpack-dev-server@5.2.2 and memfs@4.43.0), a white page with Cannot GET / appears and any files generated by webpack which aren't already present in the directory specified by devServer.static are not available.

webpack.config.js:

module.exports = (env, argv) => {
    const isDevelopment = argv.mode === 'development';

    return {
        entry: path.resolve(__dirname, 'src', 'index.ts'),
        output: {
            path: path.resolve(__dirname, 'dist'),
            filename: 'output.js',
            clean: !isDevelopment
        },
        devtool: isDevelopment ? 'source-map' : false,
        module: {
            rules: [
                {
                    test: /\.tsx?$/,
                    use: 'ts-loader',
                    exclude: /node_modules/
                },
                {
                    test: /\.css$/,
                    use: [MiniCssExtractPlugin.loader, 'css-loader']
                }
            ]
        },
        resolve: {
            extensions: ['.ts', '.js'],
            alias: {
                '@': path.resolve(__dirname, 'src')
            }
        },
        optimization: {
            minimizer: [
                `...`,
                new CssMinimizerPlugin()
            ]
        },
        plugins: [
            new MiniCssExtractPlugin(),
            new HtmlWebpackPlugin({
                template: path.resolve(__dirname, 'src', 'html', 'index.html'),
                scriptLoading: 'defer'
            })
        ],
        devServer: {
            static: {
                directory: path.join(__dirname, 'dist')
            },
            compress: true,
            port: 9000,
            open: true,
            hot: true
        }
    }
}

Expected Behavior

Files generated during the build stage of webpack serve should be available on the server.

How Do We Reproduce?

1. Install the following depencenies (which will install memfs@4.43.0):

   {
           "@types/webpack-env": "^1.18.8",
           "css-loader": "^7.1.2",
           "css-minimizer-webpack-plugin": "^7.0.2",
           "html-webpack-plugin": "^5.6.3",
           "mini-css-extract-plugin": "^2.9.3",
           "style-loader": "^4.0.0",
           "ts-loader": "^9.5.1",
           "typescript": "^5.6.3",
           "webpack": "^5.96.1",
           "webpack-cli": "^5.1.4",
           "webpack-dev-server": "^5.2.1"
   }

2. Copy the webpack.config.js file from above
3. Create files index.ts and html/index.html in src/
4. Run webpack serve --mode development

Please paste the results of npx webpack-cli info here, and mention other relevant information

  System:
    OS: Windows 11 10.0.26100
    CPU: (12) x64 12th Gen Intel(R) Core(TM) i5-12450H
    Memory: 4.94 GB / 15.70 GB
  Binaries:
    Node: 22.14.0 - C:\Program Files\nodejs\node.EXE
    npm: 10.2.5 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Chromium (140.0.3485.66)
  Packages:
    css-loader: ^7.1.2 => 7.1.2 
    css-minimizer-webpack-plugin: ^7.0.2 => 7.0.2
    html-webpack-plugin: ^5.6.3 => 5.6.4
    ts-loader: ^9.5.1 => 9.5.4
    webpack: ^5.96.1 => 5.101.3
    webpack-cli: ^5.1.4 => 5.1.4
    webpack-dev-middleware: ^7.4.2 => 7.4.3
    webpack-dev-server: ^5.2.1 => 5.2.2

Let me know if you need the output of npm ls --all aswell.

[Mirrrek]

forgot to mention that this bug really does come from memfs version 4.43.0 since downgrading to 4.42.0 without changing anything else solves the issue

npm i --save-dev memfs@4.42.0

[stephdep1973]

Faced the same issue, I worked around it by using the following devServer configuration:

devServer: {
    ...
    devMiddleware: {
        writeToDisk: true
    }
    ...

For what it's worth!

[alexander-akait]

Looks like yes - #2173, our ci is broken

[alexander-akait]

The regression on memfs side...

[Banner-Keith]

Would it be possible to change the version spec in the package json for webpack-dev-middleware for now? Maybe like ">=4.6.0 <4.43.0 || >4.43.0 <5.0.0"

[alexander-akait]

@Banner-Keith Firstly we need to open an issue in memfs and provide the place where is the regression... Will look at this soon

[alexander-akait]

/cc @streamich I don't any big changes here, looks like streamich/memfs@da1388e brings regression on Window, linux and macos work fine

[alan-agius4]

@alexander-akait there is already an issue in memfs about this: streamich/memfs#1193 and I proposed a fix streamich/memfs#1194

[alexander-akait]

@alan-agius4 Thank you, I will do the fast fix and release with pinning version when it will be merge I will return the normal version

[alexander-akait]

Done - https://github.com/webpack/webpack-dev-middleware/releases/tag/v7.4.4

[alan-agius4]

memfs has released a fix for this in 4.43.1.

[Mirrrek]

Can confirm it works with 4.43.1, closing