Grunt Webpack

Use Webpack with Grunt.

Requirements

• Version 5 of grunt-webpack supports webpack version 4 and 5 and (optional) webpack-dev-server version 4.

Install

Install this grunt plugin next to your project's Gruntfile.js. You also need to install webpack yourself, this grunt plugin does not install webpack itself.

yarn add webpack grunt-webpack --dev
// or
// npm i webpack grunt-webpack --save-dev

If you also want to use the webpack-dev-server task you also need to install webpack-dev-server

yarn add webpack-dev-server --dev

Then add this line to your project's Gruntfile.js gruntfile:

const webpackConfig = require('./webpack.config.js');

module.exports = function(grunt) {

  // Project configuration.
  grunt.initConfig({
    ...,
    webpack: {
      myConfig: webpackConfig,
    },
    ...
  });

  grunt.loadNpmTasks('grunt-webpack');
};

Configuration

webpack-grunt offers two different tasks webpack and webpack-dev-server. Both support all webpack options as can be seen in the webpack documentation. For exceptions and additions see this list.

Both Tasks

progress

Type: bool Default: true (false if no TTY present)

Activates or deactivates the progress output of webpack.

Webpack Task

failOnError

Type: bool Default: true (false if watch mode is used)

Will terminate the grunt process when an error happens if set to true. If set to false the grunt process will not be immediately terminated on error and instead continue to run.

keepalive

Type: bool Default: false (true if watch mode is used)

When set to true the grunt process/task will be kept alive after webpack task is finished. This is especially useful for watch as this usually needs to run as long as not manually killed.

storeStatsTo

Type: string Default: null

When set the stats from webpack will be written to a variable with the name provided in this option. The variable can later be used inside of other grunt tasks with template tags <%= %>.

...
storeStatsTo: "webpackStats"

...

<%= webpackStats.hash %>
...

For more information about grunt template tags have a look at the grunt docs.

watch

Type: bool Default: undefined

Turn on watch mode. This means that after the initial build, webpack will continue to watch for changes in any of the resolved files.

Turning on watch mode also sets the following defaults:

• Default cache to true
• Default keepalive to true
• Default failOnError to false

Webpack-dev-server Task

There are no special options for this task. Some changed defaults for WebpackDevServer options are:

Examples

Webpack

imported config

This is a simple example that requires the webpack config from the config file. It also disables stats in non 'development' environments and enables watch in development.

const webpackConfig = require("./webpack.config.js");

module.exports = function (grunt) {
  grunt.initConfig({
    webpack: {
      options: {
        stats: !process.env.NODE_ENV || process.env.NODE_ENV === "development",
      },
      prod: webpackConfig,
      dev: Object.assign({ watch: true }, webpackConfig),
    },
  });

  grunt.loadNpmTasks("grunt-webpack");
};

The webpack task in this example has two targets called prod and dev. They can be renamed to everything besides options. See the grunt docs for more information about targets.

On the command line you can then do the following.

# Run webpack with the `prod` target
> NODE_ENV='production' grunt webpack:prod

# Run webpack with the `dev` target
> grunt webpack:dev

# Run webpack for all targets
> grunt webpack

For more examples and information have a look at the webpack documentation which mostly also applies here besides the noted differences above.

Lazy config loading

In some cases you might want to load the webpack config lazy. This can be done by specifying a function as the config value. The first paramter to this function will be the complete grunt config, which can be used in cases where grunt templates do not work (see below).

module.exports = function (grunt) {
  grunt.initConfig({
    webpack: {
      myconfig: () => ({
        entry: path.join(__dirname, "entry"),
        output: {
          path: __dirname,
          filename: "output.js",
        },
      }),
    },
  });

  grunt.loadNpmTasks("grunt-webpack");
};

You could also use a promise

const webpackConfig = require("./webpack.config.js");

module.exports = function (grunt) {
  grunt.initConfig({
    webpack: {
      myconfig: Promise.resolve(webpackConfig),
    },
  });

  grunt.loadNpmTasks("grunt-webpack");
};

Grunt templates

grunt-webpack supports grunt templates in all string values in it's configuration.

In the next example we use a template for output.filename.

module.exports = function (grunt) {
  grunt.initConfig({
    outputFileName: "output.js",
    webpack: {
      myconfig: {
        entry: path.join(__dirname, "entry"),
        output: {
          path: __dirname,
          filename: "<%= outputFileName %>",
        },
      },
    },
  });

  grunt.loadNpmTasks("grunt-webpack");
};

For plugins we cannot support grunt template interpolation, as plugins are class instances which we cannot modify during runtime without breaking them. If you need to use template in a string option to a plugin, you can use lazy config loading and use the supplied config. You can also use grunt inside directly to access utility methods:

module.exports = function (grunt) {
  grunt.initConfig({
    name: "Webpack",
    pkg: {
      copyright: "<%= name %>",
      version: "6.55.345",
    },
    webpack: {
      myconfig: (config) => ({
        entry: path.join(__dirname, "entry"),
        output: {
          path: __dirname,
          filename: "output.js",
        },
        plugins: [
          new webpack.BannerPlugin({
            banner: `/*! ${config.pkg.copyright} - Version ${
              config.pkg.version
            } dated ${grunt.template.today()} */`,
            raw: true,
          }),
        ],
      }),
    },
  });

  grunt.loadNpmTasks("grunt-webpack");
};

Webpack-dev-server

imported config

This is a simple example that requires the webpack config from the config file. Read how to configure webpack-dev-server in the webpack-dev-server documentation.

const webpackConfig = require("./webpack.config.js");

module.exports = function (grunt) {
  grunt.initConfig({
    "webpack-dev-server": {
      dev: webpackConfig,
    },
  });

  grunt.loadNpmTasks("grunt-webpack");
};

The webpack-dev-server task in this example has one target called dev. They can be renamed to everything besides options. See the grunt docs for more information about targets.

On the command line you can then do the following.

# Run webpack-dev-server with the `dev` target
> grunt webpack-dev-server:dev

# Run webpack for all possible targets
> grunt webpack-dev-server

For more examples and information have a look at the [webpack documentation]5] which mostly also applies here besides the noted differences above.

Troubleshooting

Circular reference detected (.plugins)

If you encounter this message it means that one of the plugins which are present in your config have circular references. This is not a bug in the plugin and is totally fine for webpack, but sadly grunt cannot handle these.

To workaround this problem use lazy config loading, by wrapping your config inside a function.

const webpackConfig = require("./webpack.config.js");

module.exports = function (grunt) {
  grunt.initConfig({
    webpack: {
      myconfig: () => webpackConfig,
    },
  });

  grunt.loadNpmTasks("grunt-webpack");
};