Conflict: Multiple assets emit to the same filename

Question

I'm a webpack rookie who wants to learn all about it. I came across a conflict when running my webpack telling me:

ERROR in chunk html [entry] app.js Conflict: Multiple assets emit to the same filename app.js

What should I do to avoid the conflict?

This is my webpack.config.js:

module.exports = {
  context: __dirname + "/app",

  entry: {
    'javascript': "./js/app.js",
    'html': "./index.html",
  },
  output: {
    path: __dirname + "/dist",
    filename: "app.js",
  },
  resolve: {
    extensions: ['.js', '.jsx', '.json']
  },
  module: {
    loaders: [
      {
        test: /\.jsx?$/,
        exclude: /node_modules/,
        loaders: ["babel-loader"]
      },
      {
        test: /\.html$/,
        loader: "file-loader?name=[name].[ext]",
      }
    ]
  }
};

Helga

what I want to know is what tool writes an error like "Conflict: Multiple assets emit to the same filename slots.js". Why would you not put the damn names of the conflicting assets in that error instead of forcing the user to track it down??? – Sulphur

Good news! The error has been updated. It now helpfully reads Conflict: Multiple chunks emit assets to the same filename main.css (chunks main and main) – Sully

Additional answers can be found here: #66454011 – Instinct

Answer 1

i'm not quite familiar with your approach so I'll show you a common way to help you out.

First of all, on your output, you are specifying the filename to app.js which makes sense for me that the output will still be app.js. If you want to make it dynamic, then just use "filename": "[name].js".

The [name] part will make the filename dynamic for you. That's the purpose of your entry as an object. Each key will be used as a name in replacement of the [name].js.

And second, you can use the html-webpack-plugin. You don't need to include it as a test.

Hillyer

it would be great if this had a sample that matched the original – Stamm

Answer 2

I had the same problem, I found it was setting a static output file name that was causing my problem, in the output object try the following object.

output:{
        filename: '[name].js',
        path: __dirname + '/build',
        chunkFilename: '[id].[chunkhash].js'
    },

This makes it so that the filenames are different and it doesn't clash.

EDIT: One thing i've recently found is that you should use a hash instead of chunkhash if using HMR reloading. I haven't dug into the root of the problem but I just know that using chunkhash was breaking my webpack config

output: {
  path: path.resolve(__dirname, 'dist'),
  filename: '[name].[hash:8].js',
  sourceMapFilename: '[name].[hash:8].map',
  chunkFilename: '[id].[hash:8].js'
};

Should work fine with HMR then :)

EDIT July 2018:

A little more information on this.

Hash This is a hash generated every time that webpack compiles, in dev mode this is good for cache busting during development but shouldn't be used for long term caching of your files. This will overwrite the Hash on every build of your project.

Chunkhash If you use this in conjunction with a runtime chunk then you can use it for long term caching, the runtime chunk will see what's changed in your source code and update the corresponding chunks hash's. It won't update others allowing for your files to be cached.

Gaullist

Hi, what the :8 stand for? thx – Reasonless

@Reasonless the first 8 characters from the file's hash – Gamut

Answer 3

I had exactly the same problem. The problem seems to occur with the file-loader. The error went away when I removed the html test and included html-webpack-plugin instead to generate an index.html file. This is my webpack.config.js file:

var path = require('path');

var HtmlWebpackPlugin = require('html-webpack-plugin');
var HTMLWebpackPluginConfig = new HtmlWebpackPlugin({
  template: __dirname + '/app/index.html',
  filename: 'index.html',
  inject: 'body'
})

module.exports = { 
  entry: {
    javascript: './app/index.js',
  },  

  output: {
    filename: 'bundle.js',
    path: __dirname + '/dist'
  },  

  module: {
    rules: [
      {   
        test: /\.jsx?$/,
        exclude: [
          path.resolve(__dirname, '/node_modules/')
        ],  
        loader: 'babel-loader'
      },  
    ]   
  },  

  resolve: {
    extensions: ['.js', '.jsx', '.json']
  },  

  plugins: [HTMLWebpackPluginConfig]
}

The html-webpack-plugin generates an index.html file and automatically injects the bundled js file into it.

Wellfound

This solved my issue as well. It seems you can have the HTMLWebpackPlugin, or the html-loader, but not both. – Tempt

Answer 4

I had the same issue after upgrading to Webpack 5. My problem was caused by the copy-webpack-plugin.

Below is the original pattern ignoring a specified file, it works with Webpack 4, but throws an error with Webpack 5.

ERROR in Conflict: Multiple assets emit different content to the same filename default.hbs

  plugins: [
   new CopyPlugin({
      patterns: [
        {
          from: "./src/academy/templates",
          globOptions: {
            ignore: ["default.hbs"]
          }
        },
      ]
    }),
   ],

To fix the error:

  plugins: [
   new CopyPlugin({
      patterns: [
        {
          from: "./src/academy/templates",
          globOptions: {
            ignore: ["**/default.hbs"]
          }
        },
      ]
    }),
   ],

By not ignoring the specified file, the default.hbs (a.k.a index.html) was copied twice into the build (a.k.a /disk) directory effectively resulting in Webpack trying to insert multiple assets into the "same" (duplicated) filename.

Blotter

Answer 5

I had the same problem, and I found these in the documents.

If your configuration creates more than a single “chunk” (as with multiple entry points or when using plugins like CommonsChunkPlugin), you should use substitutions to ensure that each file has a unique name.

• [name] is replaced by the name of the chunk.
• [hash] is replaced by the hash of the compilation.
• [chunkhash] is replaced by the hash of the chunk.

 output: {
    path:__dirname+'/dist/js',

    //replace filename:'app.js' 
    filename:'[name].js'
}

Fibroma

Answer 6

If you getting same kind error in Angular

Solution : delete cache folder inside .angular folder and start portal again ng serve

Kinna

Removed all the .angular folder and everything went well :) – Telencephalon

Answer 7

In my case the source map plugin was conflicting with the extract mini plugin. Could not find a solution to this anywhere. source maps for css and javascript were writing to the same file. Here is how I finally solved it in my project:

new webpack.SourceMapDevToolPlugin({
    filename: '[name].[ext].map'
}),

Toandfro

Answer 8

I had the same problem after updating all the dependencies to latest (e.g. webpack 4 -> 5) for a Chrome extension I made about 2 years ago, and managed to solve it.

There were two files in the complaint (popup.html and options.html). Here is my original webpack.config.js file:

const path = require('path');
const CopyPlugin = require('copy-webpack-plugin');
const HtmlWebpackPlugin = require("html-webpack-plugin");
const { CleanWebpackPlugin } = require("clean-webpack-plugin");

module.exports = {
    target: 'web',
    output: {
        path: path.resolve(__dirname, 'dist'),
        filename: '[name].js',
    },
    entry: {
        popup: './src/scripts/popup.tsx',
        options: './src/scripts/options.tsx',
    },
    context: path.join(__dirname),
    module: {
        rules: [
            {
                test: /\.tsx?$/,
                loader: 'ts-loader',
            },
            {
                test: /\.css$/,
                use: [
                    'style-loader',
                    'css-loader',
                ],
            },
            {
                test: /\.scss$/,
                use: [
                    'style-loader',
                    'css-loader',
                    'sass-loader',
                ],
            },
        ],
    },

    resolve: {
        extensions: ['.tsx', '.ts', '.js', '.json', '.css'],
    },
    plugins: [
        new CleanWebpackPlugin(),
        new CopyPlugin([
            { from: 'src/popup.html', to: 'popup.html' },
            { from: 'src/options.html', to: 'options.html' },
            { from: 'src/manifest.json', to: 'manifest.json' },
            { from: 'src/icons', to: 'icons' },
        ]),
        new HtmlWebpackPlugin({
            template: path.join("src", "popup.html"),
            filename: "popup.html",
            chunks: ["popup"]
        }),
        new HtmlWebpackPlugin({
            template: path.join("src", "options.html"),
            filename: "options.html",
            chunks: ["options"]
        }),
    ]
};

I solved it by removing:

            { from: 'src/popup.html', to: 'popup.html' },
            { from: 'src/options.html', to: 'options.html' },

under new CopyPlugin... part.

So seems like right now there is no need to explicitly copy popup.html and options.html to output folder when HtmlWebpackPlugin is already emitting them.

Luthuli

Answer 9

I encountered this error in my local dev environment. For me, the solution to this error was to force the files to rebuild. To do this, I made a minor change to one of my CSS files.

I reloaded my browser and the error went away.

Delgadillo

Wanted to use asyncComponent. Then I found this problem with a file which was before in other component. Simple restarting yarn fixed that. Thanks! – Gauche

Answer 10

Similar solution to the above with file-loader, however, I think this solution is the more elegant. Before, I was only specifying the [name], adding the [path][name] resolved my conflict as below:

module: {
rules: [
  {
    test: /\.(mp4|m4s)$/,
    use: [
      {
        loader: 'file-loader',
        options: {
          name: '[path][name].[ext]',
        },
      },
    ],
  },
],

Haystack

Answer 11

I changed index.html file from /public directory to /src to fix this issue. (Webpack 5.1.3)

Protective

Answer 12

webpack 5 solution

Add chunkFilename and assetModuleFilename in output as showed below.

  output: {
    path: path.join(__dirname, "/build/"),
    filename: "js/[name].[contenthash].js",
    chunkFilename: 'chunks/[name].[chunkhash].js',
    assetModuleFilename: 'media/[name][hash][ext][query]'
  },

Ayana

Answer 13

The same error in a Vue.js project when doing e2e with Karma. The page was served using a static template index.html with /dist/build.js. And got this error running Karma.

The command to issue Karma using package.json was:

"test": "cross-env BABEL_ENV=test CHROME_BIN=$(which chromium-browser) karma start --single-run"

The output configuration in webpack.config.js was:

 module.exports = {
  output: {
   path: path.resolve(__dirname, './dist'),
   publicPath: '/dist/',
   filename: 'build.js'
  },
  ...
 }

My solution: inspired by the Evan Burbidge's answer I appended the following at the end of webpack.config.js:

if (process.env.BABEL_ENV === 'test') {
  module.exports.output.filename = '[name].[hash:8].js'
}

And then it eventually worked for both page serving and e2e.

Binoculars

Answer 14

I had a similar problem while upgrading webpack 3 to webpack 4. After upgrading the modules I came across this error.

WARNING in Conflict: Multiple assets emit different content to the same filename alert-icon.svg

WARNING in Conflict: Multiple assets emit different content to the same filename comment.svg

The problem was caused by fileloader for svg. Solved the error by adding a hash name: '[name].[hash:8].[ext]' making it unique every time webpack compiles.

Provinding the code below:

module: {
rules: [
  {
  test: /\.svg$/,
  loader: 'file-loader',
  query: {
    name: '[name].[hash:8].[ext]'
  }  
]   

}

Phonometer

Answer 15

Everything is working. I found a bug in the function - I used straight quotes instead of slashes. With slashes everything works correctly.

The reason was the wrong quotes and webpack creates Bundel.${ext} - files in any mode, but with the correct quotes I get Bunle.js and Bundle.scss, or them with a hash. All working with simple [hash] without 8.

Marlborough

As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center. – Constructive