Custom webpack builders for Angular build facade

Allow customizing build configuration without ejecting webpack configuration (ng eject)

Prerequisites:

• Angular CLI 6
• @angular-devkit/build-angular >= 0.10.0

Usage

1. npm i -D @angular-builders/custom-webpack
2. In your angular.json:

   "projects": {
       ...
       "[project]": {
            ...
            "architect": {
                   ...
                   "[architect-target]": {
                             "builder": "@angular-builders/custom-webpack:[browser|server|karma|extract-i18n]"
                             "options": {
                                   ...
                             }

   Where:
   • [project] is the name of the project to which you want to add the builder
   • [architect-target] is the name of build target you want to run (build, serve, test etc. or any custom target)
   • [browser|server|karma|extract-i18n] one of the supported builders - browser, server, karma or extract-i18n
3. If [architect-target] is not one of the predefined targets (like build, serve, test etc.) then run it like this:
   ng run [project]:[architect-target]
   If it is one of the predefined targets, you can run it with ng [architect-target]

For example

• angular.json:

  "projects": {
      ...
      "example-app": {
           ...
           "architect": {
                  ...
                  "build": {
                            "builder": "@angular-builders/custom-webpack:browser"
                            "options": {
                                  ...
                            }

• Run the build: ng build

Builders

• @angular-builders/custom-webpack:browser
• @angular-builders/custom-webpack:server
• @angular-builders/custom-webpack:karma
• @angular-builders/custom-webpack:extract-i18n

Custom webpack browser

Extended @angular-devkit/build-angular:browser builder that allows to specify additional webpack configuration (on top of the existing under the hood). The builder will run the same build as @angular-devkit/build-angular:browser does with extra parameters that are specified in the provided webpack configuration.

Builder options:

• All the @angular-devkit/build-angular:browser options
• customWebpackConfig: see below

angular.json Example:

"architect": {
    ...
    "build": {
              "builder": "@angular-builders/custom-webpack:browser"
              "options": {
                     "customWebpackConfig": {
                        "path": "./extra-webpack.config.js",
                        "mergeStrategies": { "externals": "replace" }
                     }
                     "outputPath": "dist/my-cool-client",
                     "index": "src/index.html",
                     "main": "src/main.ts",
                     "polyfills": "src/polyfills.ts",
                     "tsConfig": "src/tsconfig.app.json"
              }

In this example externals entry from extra-webpack.config.js will replace externals entry from Angular CLI underlying webpack config.

Custom webpack server

Extended @angular-devkit/build-angular:server builder that allows to specify additional webpack configuration (on top of the existing under the hood). The builder will run the same build as @angular-devkit/build-angular:server does with extra parameters that are specified in the provided webpack configuration.

Builder options:

• All the @angular-devkit/build-angular:server options
• customWebpackConfig: see below

angular.json Example:

"architect": {
    ...
    "build": {
              "builder": "@angular-builders/custom-webpack:server"
              "options": {
                     "customWebpackConfig": {
                        "path": "./extra-webpack.config.js",
                        "mergeStrategies": { "module.rules": "prepend" },
                        "replaceDuplicatePlugins": true
                     }
                    "outputPath": "dist/my-cool-server",
                    "main": "src/main.server.ts",
                    "tsConfig": "src/tsconfig.server.json"
              }

In this example module.rules entry from extra-webpack.config.js will be prepended to module.rules entry from Angular CLI underlying webpack config.
Since loaders are evaluated from right to left this will effectively mean that the loaders you define in your custom configuration will be applied after the loaders defined by Angular CLI.

Custom webpack Karma

Extended @angular-devkit/build-angular:karma builder that allows to specify additional webpack configuration (on top of the existing under the hood). The builder will run the same build as @angular-devkit/build-angular:karma does with extra parameters that are specified in the provided webpack configuration.

Builder options:

• All the @angular-devkit/build-angular:karma options
• customWebpackConfig: see below

angular.json Example:

"architect": {
    ...
    "test": {
              "builder": "@angular-builders/custom-webpack:karma"
              "options": {
                     "customWebpackConfig": {
                        "path": "./extra-webpack.config.js"
                     }
                    "main": "src/test.ts",
                    "polyfills": "src/polyfills.ts",
                    "tsConfig": "src/tsconfig.spec.json",
                    "karmaConfig": "src/karma.conf.js",
                    ...
              }

Custom webpack Extract i18n

Extended @angular-devkit/build-angular:extract-i18n builder that allows to specify additional webpack configuration (on top of the existing under the hood). The builder will run the same build as @angular-devkit/build-angular:extract-i18n does with extra parameters that are specified in the provided webpack configuration.

Builder options:

• All the @angular-devkit/build-angular:extract-i18n options
• customWebpackConfig: see below

angular.json Example:

"architect": {
    ...
    "build": {
              "builder": "@angular-builders/custom-webpack:extract-i18n"
              "options": {
                    "browserTarget": "my-cool-angular-app-arch:build",
                    "customWebpackConfig": {
                        "path": "./extra-webpack.config.js",
                        "mergeStrategies": { "module.rules": "prepend" },
                        "replaceDuplicatePlugins": true
                     }
              }

In this example module.rules entry from extra-webpack.config.js will be prepended to module.rules entry from Angular CLI underlying webpack config.
Since loaders are evaluated from right to left this will effectively mean that the loaders you define in your custom configuration will be applied after the loaders defined by Angular CLI.

Custom webpack config object

This option defines your custom webpack configuration. If not specified at all, plain Angular build will run.
The following properties are available:

• path: path to the extra webpack configuration, defaults to webpack.config.js. The configuration file can export either an object or a function. If it is an object it shall contain only modifications and additions, you don't have to specify the whole webpack configuration.
  Thus, if you'd like to add some options to style-loader (which already there because of default Angular configuration), you only have to specify this part of the loader:

   {
     test: /\.css$/,
     use: [
       {loader: 'style-loader', options: {...}}
     ]
   }

  The builder will take care of merging the delta with the existing configuration provided by Angular.
  In more complicated cases you'd probably want to use a function instead of an object.

• mergeStrategies: webpack config merge strategies, can be append | prepend | replace per webpack config entry. Defaults to append.

  • append: appends the given entry configuration (in custom webpack config) to the existing Angular CLI webpack configuration.
  • prepend: prepends the given entry configuration (in custom webpack config) to the existing field configuration (in Angular CLI webpack config). The custom loaders config will be added to the beginning of the existing loaders array.
  • replace: replaces the given entry configuration entirely. The custom webpack config will replace the Angular CLI webpack config (for this particular entry). See webpack-merge for more info.

• replaceDuplicatePlugins: Defaults to false. If true, the plugins in custom webpack config will replace the corresponding plugins in default Angular CLI webpack configuration. If false, the default behavior will be applied. Note that if true, this option will override mergeStrategies for plugins field.

Merging plugins configuration:

If in your custom configuration you specify a plugin that is already added by Angular CLI then by default the two instances will be merged.
In case of the conflicts your configuration will override the existing one.
Thus, if you'd like to modify an existing plugin configuration, all you have to do is specify the delta you want to change.
For example, if you'd like to add an additional entry in excludeChunks list of HtmlWebpackPlugin you only have to specify this single entry:

 new HtmlWebpackPlugin({
    "excludeChunks": [
      "webworker"
    ]
 })

Keep in mind though that if there are default values in the plugin's constructor, they would override the corresponding values in the existing instance. So these you have to set explicitly to the same values Angular sets.
You can check out an example for plugins merge in the unit tests and in this issue.

Custom Webpack config function

If customWebpackConfig.path file exports a function, the behaviour of the builder changes : no more automatic merge is applied, instead the function is called with the base Webpack configuration and must return the new configuration.

The function is called with the base config and the builder options as parameters.

In this case, mergeStrategies and replaceDuplicatePlugins options have no effect.

custom-webpack.config.js example :

const webpack = require('webpack');
const pkg = require('./package.json');

module.exports = (config, options) => {
  config.plugins.push(
    new webpack.DefinePlugin({
      'APP_VERSION': JSON.stringify(pkg.version),
    }),
  );

  return config;
};

Further reading

• Customizing Angular CLI 6 build  -  an alternative to ng eject