Bundlers

A comprehensive guide for configuring different bundlers with Aurelia 2 applications, including Webpack, Vite, and Parcel.

Aurelia is a framework that prides itself on flexibility and minimal boilerplate. This flexibility extends to how you bundle and build your application. Whether you prefer Webpack, Vite, Parcel, or another bundler, Aurelia 2 offers a straightforward approach to configuration.

Bundling is the process of gathering your source code, templates, styles, and related assets into optimized sets of files that are easier for browsers to load. Below, we'll walk through common bundler choices in Aurelia 2 and how to integrate them.

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Webpack

Webpack is a powerful and widely used bundler that allows deep customization of your build. Below is an overview of how to set up and configure a basic Aurelia 2 app with Webpack.

Installing Webpack

npm install --save-dev webpack webpack-cli webpack-dev-server
npm install --save-dev @aurelia/webpack-loader ts-loader

The @aurelia/webpack-loader is essential for properly processing Aurelia's HTML templates and TypeScript files with Aurelia-specific transformations.

Tip: If you are migrating from Aurelia 1, you may already have a webpack.config.js that you can adapt for Aurelia 2, but you'll need to update the loader configuration.

Basic Configuration

Here's a complete webpack configuration for Aurelia 2:

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');

module.exports = function(env, { mode }) {
  const production = mode === 'production';

  return {
    target: 'web',
    mode: production ? 'production' : 'development',
    devtool: production ? 'source-map' : 'eval-cheap-source-map',
    entry: {
      app: './src/main.ts'
    },
    output: {
      path: path.resolve(__dirname, 'dist'),
      filename: production ? '[name].[contenthash].bundle.js' : '[name].bundle.js'
    },
    resolve: {
      extensions: ['.ts', '.js'],
      modules: [path.resolve(__dirname, 'src'), 'node_modules']
    },
    devServer: {
      historyApiFallback: true,
      open: !process.env.CI,
      port: 9000
    },
    module: {
      rules: [
        // Asset loaders
        { test: /\.(png|gif|jpg|cur)$/i, loader: 'url-loader', options: { limit: 8192 } },
        { test: /\.woff2(\?v=[0-9]\.[0-9]\.[0-9])?$/i, loader: 'url-loader', options: { limit: 10000, mimetype: 'application/font-woff2' } },
        { test: /\.woff(\?v=[0-9]\.[0-9]\.[0-9])?$/i, loader: 'url-loader', options: { limit: 10000, mimetype: 'application/font-woff' } },
        { test: /\.(ttf|eot|svg|otf)(\?v=[0-9]\.[0-9]\.[0-9])?$/i, loader: 'file-loader' },

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

        // TypeScript + Aurelia loader
        {
          test: /\.ts$/i,
          use: ['ts-loader', '@aurelia/webpack-loader'],
          exclude: /node_modules/
        },

        // Aurelia HTML templates
        {
          test: /\.html$/i,
          use: '@aurelia/webpack-loader',
          exclude: /node_modules/
        }
      ]
    },
    plugins: [
      new HtmlWebpackPlugin({ template: 'index.html' })
    ]
  };
};

Advanced Configuration Options

Development Aliases

For development, you can alias Aurelia packages to their development builds for better debugging:

// In resolve.alias section
alias: {
  ...[
    'aurelia',
    'fetch-client',
    'kernel',
    'metadata',
    'platform',
    'platform-browser',
    'route-recognizer',
    'router',
    'router',
    'runtime',
    'runtime-html',
    'testing',
    'state',
    'ui-virtualization'
  ].reduce((map, pkg) => {
    const name = pkg === 'aurelia' ? pkg : `@aurelia/${pkg}`;
    map[name] = path.resolve(__dirname, 'node_modules', name, 'dist/esm/index.dev.mjs');
    return map;
  }, {})
}

Hot Module Replacement (HMR)

To enable HMR for Aurelia components:

// In devServer
devServer: {
  hot: true,
  historyApiFallback: true,
  port: 9000
},

// In module rules for TypeScript
{
  test: /\.ts$/i,
  use: [
    'ts-loader',
    {
      loader: '@aurelia/webpack-loader',
      options: {
        hmr: true  // Enable HMR for Aurelia
      }
    }
  ],
  exclude: /node_modules/
}

TypeScript Type Checking

For enhanced TypeScript support with template type checking:

{
  test: /\.ts$/i,
  use: [
    'ts-loader',
    {
      loader: '@aurelia/webpack-loader',
      options: {
        experimentalTemplateTypeCheck: true
      }
    }
  ],
  exclude: /node_modules/
}

Production Optimizations

• Minification: Webpack 5+ includes Terser plugin by default for production builds

• Code Splitting: Configure optimization.splitChunks for better caching

• Source Maps: Use 'source-map' for production debugging

• Content Hashing: Use [contenthash] in filenames for long-term caching

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Vite

Vite is a fast, modern bundler (and dev server) that works excellently with Aurelia. Its plugin system provides quick project startup, HMR (Hot Module Replacement), and speedy builds.

Installing

npm install --save-dev @aurelia/vite-plugin

Basic Usage

In vite.config.js:

import { defineConfig } from 'vite';
import aurelia from '@aurelia/vite-plugin';

export default defineConfig({
  plugins: [aurelia()],
});

TypeScript Support

For TypeScript apps, add this declaration file to your project (usually generated by the Aurelia CLI):

html.d.ts

declare module '*.html' {
  import { IContainer } from '@aurelia/kernel';
  import { BindableDefinition } from '@aurelia/runtime';
  export const name: string;
  export const template: string;
  export default template;
  export const dependencies: string[];
  export const containerless: boolean | undefined;
  export const bindables: Record<string, BindableDefinition>;
  export const shadowOptions: { mode: 'open' | 'closed'} | undefined;
  export function register(container: IContainer);
}

Plugin Configuration Options

The Aurelia Vite plugin accepts several configuration options:

import { defineConfig } from 'vite';
import aurelia from '@aurelia/vite-plugin';

export default defineConfig({
  plugins: [
    aurelia({
      // Always use development bundles
      useDev: true,

      // File inclusion/exclusion patterns
      include: 'src/**/*.{ts,js,html}',
      exclude: 'node_modules/**',

      // Plugin execution order
      pre: true,

      // Enable/disable conventions
      enableConventions: true,

      // HMR configuration
      hmr: true
    })
  ]
});

Development Configuration

By default, the Aurelia Vite plugin automatically uses development bundles when in development mode:

export default defineConfig({
  plugins: [
    aurelia({
      useDev: true  // Force development bundles regardless of mode
    })
  ]
});

Production & Code Splitting

Vite automatically optimizes for production. You can customize chunk splitting:

export default defineConfig({
  build: {
    rollupOptions: {
      output: {
        manualChunks: {
          'vendor': ['aurelia'],
          'router': ['@aurelia/router-direct', '@aurelia/router']
        }
      }
    }
  },
  plugins: [aurelia()]
});

Source Maps and Debugging

export default defineConfig({
  build: {
    sourcemap: true  // Enable source maps in production
  },
  plugins: [aurelia()]
});

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Parcel

Parcel is a zero-configuration bundler that works well with Aurelia 2 through the official transformer.

Installing

npm install --save-dev @aurelia/parcel-transformer
npm install --save-dev @parcel/transformer-typescript-tsc  # For TypeScript projects

Configuration

Create a .parcelrc file in your project root:

{
  "extends": "@parcel/config-default",
  "transformers": {
    "*.ts": ["@aurelia/parcel-transformer", "@parcel/transformer-typescript-tsc"],
    "*.html": ["@aurelia/parcel-transformer", "..."]
  }
}

For JavaScript projects:

{
  "extends": "@parcel/config-default",
  "transformers": {
    "*.js": ["@aurelia/parcel-transformer", "..."],
    "*.html": ["@aurelia/parcel-transformer", "..."]
  }
}

Package.json Configuration

You can configure Aurelia-specific options in your package.json:

{
  "aurelia": {
    "hmr": true,
    "defaultShadowOptions": { "mode": "open" },
    "useCSSModule": false
  }
}

TypeScript Support

For TypeScript projects, add the same html.d.ts declaration file mentioned in the Vite section.

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CSS and Styling

CSS Modules

Aurelia supports CSS modules with proper bundler configuration:

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

// Vite (built-in support)
// Just name your files with .module.css extension

SCSS/SASS Support

Add SASS loaders for SCSS support:

npm install --save-dev sass sass-loader  # Webpack
npm install --save-dev sass              # Vite (built-in)

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Troubleshooting

Common Issues

"Cannot resolve module" errors

• Ensure file extensions are properly configured in bundler resolve settings

• Check that Aurelia loaders are properly configured for HTML and TypeScript files

Slow development builds

• For Webpack: Enable experiments.lazyCompilation and proper development aliases

• For Vite: Ensure useDev: true is set in the Aurelia plugin options

HMR not working

• Verify HMR is enabled in both bundler and Aurelia loader configurations

• Check browser console for HMR-related warnings

TypeScript template errors

• Ensure proper HTML type definitions are included

• Consider enabling experimentalTemplateTypeCheck in webpack loader options

Performance Tips

1. Use development bundles: Always alias to .dev.mjs files during development

2. Enable code splitting: Configure manual chunks for better loading performance

3. Optimize assets: Use appropriate loaders for images, fonts, and other assets

4. Source map strategy: Use eval-cheap-source-map for development, source-map for production

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Conclusion

Aurelia 2 provides excellent bundler flexibility through dedicated loaders and plugins. Vite offers the fastest development experience with minimal configuration, while Webpack provides maximum customization options. Parcel offers a good middle ground with zero-configuration setup.

Key points to remember:

• Always use the official Aurelia bundler plugins/loaders

• Configure proper TypeScript declarations for HTML modules

• Use development bundles during development for better debugging

• Enable HMR for the best development experience

For advanced configurations and bundler-specific optimizations, refer to the official documentation of your chosen bundler alongside Aurelia's guides.