Custom webpack builders for Angular build facade

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

Table of Contents

Usage
- For Example
Builders
Custom Webpack Config Object
Index Transform
- Example
ES Modules (ESM) Support
Verbose Logging
Further Reading

This documentation is for the latest major version only

Previous versions

Click to expand

Quick guide

Prerequisites:

Angular CLI 20

Usage

npm i -D @angular-builders/custom-webpack
In your angular.json:
```
"projects": {
  ...
  "[project]": {
    ...
    "architect": {
      ...
      "[architect-target]": {
        "builder": "@angular-builders/custom-webpack:[browser|server|karma|dev-server|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|dev-server|extract-i18n] one of the supported builders - browser, server, karma, dev-server or extract-i18n
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:dev-server
@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) and index.html transformations. 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. It will also run transformation on index.html if specified.

Builder options:

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

angular.json Example:

"architect": {
  ...
  "build": {
    "builder": "@angular-builders/custom-webpack:browser",
    "options": {
      "customWebpackConfig": {
        "path": "./extra-webpack.config.js",
        "mergeRules": {
          "externals": "replace"
        }
      },
      "indexTransform": "./index-html-transform.js",
      "outputPath": "dist/my-cool-client",
      "index": "src/index.html",
      "main": "src/main.ts",
      "polyfills": ["zone.js"],
      "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 while all the rest will be appended. In addition index.html will be modified by the function exported from ./index-html-transform.js.

Custom Webpack `dev-server`

Enhanced @angular-devkit/build-angular:dev-server builder that leverages the custom webpack builder to get webpack configuration.

Unlike the default @angular-devkit/build-angular:dev-server it doesn't use @angular-devkit/build-angular:browser configuration to run the dev server. Instead it uses customWebpackConfiguration from browserTarget and runs custom webpack dev server build.

Thus, if you use @angular-builders/custom-webpack:dev-server along with @angular-builders/custom-webpack:browser, ng serve will run with custom configuration provided in the latter.

Example

angular.json:

"architect": {
  ...
  "build": {
    "builder": "@angular-builders/custom-webpack:browser",
    "options": {
      "customWebpackConfig": {
         "path": "./extra-webpack.config.js"
      },
      ...
    }
  },
  "serve": {
    "builder": "@angular-builders/custom-webpack:dev-server",
    "options": {
      "buildTarget": "my-project:build"
    }
  }

In this example dev-server will use custom-webpack:browser builder, hence modified webpack config, when invoking the serve target.

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) and index.html transformations. 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",
        "mergeRules": {
          "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 while all the rest will be appended. 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) and index.html transformations. 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": ["zone.js"],
      "tsConfig": "src/tsconfig.spec.json",
      "karmaConfig": "src/karma.conf.js",
    }

External karma.conf.js configuration:

Starting with Angular v20, generating an external karma config will cause tests to hang while utilizing @angular-builders/custom-webpack:karma.

Fix this by:

adding '@angular-devkit/build-angular' to the frameworks array
adding '@angular-devkit/build-angular/plugins/karma' to the plugins array

karma.conf.js example:

module.exports = function (config) {
  config.set({
    basePath: '',
    frameworks: ['jasmine', '@angular-devkit/build-angular'],
    plugins: [
      require('karma-jasmine'),
      require('karma-chrome-launcher'),
      require('karma-jasmine-html-reporter'),
      require('karma-coverage'),
      require('@angular-devkit/build-angular/plugins/karma'),
    ],
    // ...

Custom Webpack `extract-i18n`

Enhanced @angular-devkit/build-angular:extract-i18n builder that leverages the custom webpack builder to get webpack configuration.

The builder uses customWebpackConfiguration from browserTarget to run the extraction process while taking into account changes in your custom webpack config.

Thus, if you use @angular-builders/custom-webpack:extract-i18n along with @angular-builders/custom-webpack:browser, ng extract-i18n will run with custom configuration provided in the latter.

Example

angular.json:

"architect": {
  ...
  "build": {
    "builder": "@angular-builders/custom-webpack:browser",
    "options": {
      "customWebpackConfig": {
         "path": "./extra-webpack.config.js"
      },
      ...
    }
  },
  "extract-i18n": {
    "builder": "@angular-builders/custom-webpack:extract-i18n",
    "options": {
      "buildTarget": "my-project:build"
    }
  }

In this example extract-i18n will use custom-webpack:browser builder, hence modified webpack config, when invoking the extract-i18n target.

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: {
        // `style-loader` options here...
      }
    }
  ]
}
```
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.

mergeRules: webpack config merge rules, as described here. Defaults to:

{
  module: {
    rules: {
      test: "match",
      use: {
        loader: "match",
        options: "merge",
      },
    },
  },
};

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 mergeRules for plugins field.

Webpack configuration can be also written in TypeScript. In this case, it is the application's tsConfig file which will be used by tsnode for customWebpackConfig.ts execution. Given the following example:

// extra-webpack.config.ts
import { Configuration } from 'webpack';

export default {
  output: {
    library: 'shop',
    libraryTarget: 'umd',
  },
} as Configuration;

Do not forget to specify the correct path to this file:

"customWebpackConfig": {
  "path": "./extra-webpack.config.ts"
},

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 allow cyclic dependencies that include dynamic imports you only have to specify this single entry:

module.exports = {
  plugins: [
    new CircularDependencyPlugin({
      allowAsyncCycles: true,
    }),
  ],
};

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 Promisified Config

Webpack config can also export a Promise object that resolves custom config. Given the following example:

// extra-webpack.config.js
const fs = require('fs');
const util = require('util');
const webpack = require('webpack');

const readFile = util.promisify(fs.readFile);

module.exports = readFile('./LICENSE', {
  encoding: 'utf-8',
}).then(license => ({
  plugins: [new webpack.BannerPlugin(license)],
}));

In this case, the behavior will be the same as when exporting a plain object — the resolved configuration will be merged with the base one.

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, the builder options, and the target options as parameters. TargetOptions follows target definition from this schema and can be used to manipulate your build based on the build target.

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

custom-webpack.config.js example :

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

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

  return config;
};

Alternatively, using TypeScript:

import { CustomWebpackBrowserSchema, TargetOptions } from '@angular-builders/custom-webpack';
import * as webpack from 'webpack';
import * as pkg from './package.json';

export default (
  config: webpack.Configuration,
  options: CustomWebpackBrowserSchema,
  targetOptions: TargetOptions
) => {
  config.plugins.push(
    new webpack.DefinePlugin({
      APP_VERSION: JSON.stringify(pkg.version),
    })
  );

  return config;
};

It's also possible to export an asynchronous factory (factory that returns a Promise object). Let's look at the following example:

// extra-webpack.config.js
const axios = require('axios');
const webpack = require('webpack');

async function getPortalVersion() {
  const response = await axios.get('http://portal.com/version');
  return response.data.version;
}

module.exports = async config => {
  const version = await getPortalVersion();

  config.plugins.push(
    new webpack.DefinePlugin({
      APP_VERSION: JSON.stringify(version),
    })
  );

  return config;
};

Index Transform

Since Angular 8 index.html is not generated as part of the Webpack build. If you want to modify your index.html you should use indexTransform option.
indexTransform is a path (relative to workspace root) to a .js or .ts file that exports transformation function for index.html.
Function signature is as following: If indexTransform is written in TypeScript, it is the application's tsConfig file which will be use by tsnode for indexTransform.ts execution.

(options: TargetOptions, indexHtmlContent: string) => string | Promise<string>;

or, in other words, the function receives target options and original index.html content (generated by Angular CLI) and returns a new content as string or Promise.
TargetOptions follows target definition from this schema and looks like this:

export interface Target {
  configuration?: string;
  project: string;
  target: string;
}

It is useful when you want to transform your index.html according to the build options.

Example

angular.json:

"architect": {
  ...
  "build": {
    "builder": "@angular-builders/custom-webpack:browser",
    "options": {
      "indexTransform": "./index-html-transform.js"
      ...
    }

index-html-transform.js:

module.exports = (targetOptions, indexHtml) => {
  const i = indexHtml.indexOf('</body>');
  const config = `<p>Configuration: ${targetOptions.configuration}</p>`;
  return `${indexHtml.slice(0, i)}
            ${config}
            ${indexHtml.slice(i)}`;
};

Alternatively, using TypeScript:

import { TargetOptions } from '@angular-builders/custom-webpack';

export default (targetOptions: TargetOptions, indexHtml: string) => {
  const i = indexHtml.indexOf('</body>');
  const config = `<p>Configuration: ${targetOptions.configuration}</p>`;
  return `${indexHtml.slice(0, i)}
            ${config}
            ${indexHtml.slice(i)}`;
};

In the example we add a paragraph with build configuration to your index.html. It is a very simple example without any asynchronous code but you can also return a Promise from this function.

Full example here.

ES Modules (ESM) Support

Custom Webpack builder fully supports ESM.

If your app has "type": "module" both custom-webpack.js and index-transform.js will be treated as ES modules, unless you change their file extension to .cjs. In that case they'll be treated as CommonJS Modules. Example.
For "type": "commonjs" (or unspecified type) both custom-webpack.js and index-transform.js will be treated as CommonJS modules unless you change their file extension to .mjs. In that case they'll be treated as ES Modules. Example.
If you want to use TS config in ESM app, you must set the loader to ts-node/esm when running ng build. Also, in that case tsconfig.json for ts-node no longer defaults to tsConfig from the browser target - you have to specify it manually via environment variable. Example.
Note that tsconfig paths are not supported in TS configs within ESM apps. That is because tsconfig-paths do not support ESM.

Verbose Logging

Custom Webpack allows enabling verbose logging for configuration properties. This can be achieved by providing the verbose object in builder options. Given the following example:

{
  "builder": "@angular-builders/custom-webpack:browser",
  "options": {
    "customWebpackConfig": {
      "verbose": {
        "properties": ["entry"]
      }
    }
  }
}

properties is an array of strings that supports individual or deeply nested keys (output.publicPath and plugins[0] are valid keys). The number of times to recurse the object while formatting before it's logged is controlled by the serializationDepth property:

{
  "builder": "@angular-builders/custom-webpack:browser",
  "options": {
    "customWebpackConfig": {
      "verbose": {
        "properties": ["plugins[0]"],
        "serializationDepth": 5
      }
    }
  }
}

Further Reading

Customizing Angular CLI build - an alternative to ng eject

Uh oh!