Custom ESBuild builders for Angular build facade

Allow customizing ESBuild configuration

Table of Contents

Usage
- For Example
Builders
- Custom ESBuild application
  - Example
- Custom ESBuild dev-server
  - Example
Index Transform
- Example
ES Modules (ESM) Support

This documentation is for the latest major version only

Previous versions

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Prerequisites:

Angular CLI 20

Usage

npm i -D @angular-builders/custom-esbuild

In your angular.json:

"projects": {
  ...
  "[project]": {
    ...
    "architect": {
      ...
      "[architect-target]": {
        "builder": "@angular-builders/custom-esbuild:[application|dev-server]",
        "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)
[application|dev-server] one of the supported builders - application or dev-server

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-esbuild:browser",
        "options": {
          ...
        }

Run the build: ng build

Builders

@angular-builders/custom-esbuild:application
@angular-builders/custom-esbuild:dev-server

Custom ESBuild `application`

The @angular-builders/custom-esbuild:application builder is an extension of the @angular-devkit/build-angular:application builder, allowing the specification of additional properties on top of the existing ones. The custom builder runs the original builder at the end, incorporating extra parameters specified in the extended configuration. It will also perform index.html transformations if specified.

Builder options:

All the @angular-devkit/build-angular:application options
plugins
indexHtmlTransformer: see below

Example

angular.json:

"architect": {
  ...
  "build": {
    "builder": "@angular-builders/custom-esbuild:application",
    "options": {
      "plugins": ["./esbuild/plugins.ts", { "path": "./esbuild/define-env.ts", "options": { "stage": "development" } }],
      "indexHtmlTransformer": "./esbuild/index-html-transformer.js",
      "outputPath": "dist/my-cool-client",
      "index": "src/index.html",
      "browser": "src/main.ts",
      "polyfills": ["zone.js"],
      "tsConfig": "src/tsconfig.app.json"
    },
    "configurations": {
      "production": {
        "plugins": ["./esbuild/plugins.ts", { "path": "./esbuild/define-env.ts", "options": { "stage": "production" } }]
      }
    }
  }

In the above example, we specify the list of plugins that should implement the ESBuild plugin schema. These plugins are custom user plugins and are added to the original ESBuild Angular configuration. Additionally, the indexHtmlTransformer property is used to specify the path to the file that exports the function used to modify the index.html.

The plugin file can export either a single plugin, a list of plugins or a factory function that returns a plugin or list of plugins. If a plugin accepts configuration then the config should be provided in angular.json:

// esbuild/plugins.ts
import type { Plugin, PluginBuild } from 'esbuild';

const defineTextPlugin: Plugin = {
  name: 'define-text',
  setup(build: PluginBuild) {
    const options = build.initialOptions;
    options.define.buildText = JSON.stringify('This text is provided during the compilation');
  },
};

export default defineTextPlugin;

OR:

// esbuild/plugins.ts
import type { Plugin, PluginBuild } from 'esbuild';

function defineEnv(pluginOptions: { stage: string }): Plugin {
  return {
    name: 'define-env',
    setup(build: PluginBuild) {
      const buildOptions = build.initialOptions;
      buildOptions.define.stage = JSON.stringify(pluginOptions.stage);
    },
  };
}

export default defineEnv;

Or:

// esbuild/plugins.ts
import type { Plugin, PluginBuild } from 'esbuild';

const defineTextPlugin: Plugin = {
  name: 'define-text',
  setup(build: PluginBuild) {
    const options = build.initialOptions;
    options.define.buildText = JSON.stringify('This text is provided during the compilation');
  },
};

const updateExternalPlugin: Plugin = {
  name: 'update-external',
  setup(build: PluginBuild) {
    const options = build.initialOptions;
    options.external ??= [];
    options.external.push('elysia');
  },
};

export default [defineTextPlugin, updateExternalPlugin];

Or:

// esbuild/plugins.ts
import type { Plugin, PluginBuild } from 'esbuild';
import type { ApplicationBuilderOptions } from '@angular-devkit/build-angular';
import type { Target } from '@angular-devkit/architect';

export default (builderOptions: ApplicationBuilderOptions, target: Target): Plugin => {
  return {
    name: 'define-text',
    setup(build: PluginBuild) {
      const options = build.initialOptions;
      options.define.currentProject = JSON.stringify(target.project);
    },
  };
};

Custom ESBuild `dev-server`

The @angular-builders/custom-esbuild:dev-server is an enhanced version of the @angular-devkit/build-angular:dev-server builder that allows the specification of middlewares (Vite's Connect functions). It also obtains plugins and indexHtmlTransformer from the :application configuration to run the Vite server with all the necessary configuration applied.

Example

angular.json:

"architect": {
  ...
  "build": {
    "builder": "@angular-builders/custom-esbuild:application",
    "options": {
      "plugins": ["./esbuild/plugin-1.js"]
      ...
    }
  },
  "serve": {
    "builder": "@angular-builders/custom-esbuild:dev-server",
    "options": {
      "middlewares": ["./esbuild/my-middleware.js"],
      "buildTarget": "my-project:build"
    }
  }

Index Transform

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

(indexHtmlContent: string, target: Target) => 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<string>.

The indexHtmlTransformer function signature is defined here.

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-esbuild:application",
    "options": {
      "indexHtmlTransformer": "./esbuild/index-html-transformer.js"
      ...
    }

index-html-transformer.js:

module.exports = indexHtml => {
  const i = indexHtml.indexOf('</body>');
  const content = `<p>Dynamically inserted content</p>`;
  return `${indexHtml.slice(0, i)}
            ${content}
            ${indexHtml.slice(i)}`;
};

Alternatively, using TypeScript:

export default (indexHtml: string) => {
  const i = indexHtml.indexOf('</body>');
  const content = `<p>Dynamically inserted content</p>`;
  return `${indexHtml.slice(0, i)}
            ${content}
            ${indexHtml.slice(i)}`;
};

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

ES Modules (ESM) Support

Custom ESBuild builder fully supports ESM.

If your app has "type": "module" both plugin.js and index-html-transformer.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 plugin.js and index-html-transformer.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 application 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.

Uh oh!