I have angular application which works independently. Also there is a flutter web build for a certain feature which runs independently. I would like to use the flutter web build as a micro frontend which can be viewed in angular shell application using angular routes. Was thinking of using Webpack module federation plugin to do so. Is this possible to achieve using Webpack module federation plugin?
Since there are not many resources regarding Webpack plugin to be used with flutter, any help will be greatly appreciated.
Okay, here\’s a breakdown of how you can approach integrating a Flutter web build as a micro frontend into your Angular application using Webpack Module Federation, along with considerations and potential alternatives, crafted as a professional software engineer would:\n\n**Yes, it\’s possible to achieve this using Webpack Module Federation, although there are some key considerations and potential challenges due to the inherent differences between Angular and Flutter\’s build processes.**\n\nHere\’s a detailed explanation of the approach, potential problems, and how to mitigate them:\n\n**1. Core Concept: Exposing the Flutter Web App as a Remote Module**\n\n* The goal is to treat your Flutter web build as a \”remote module\” that your Angular application (\”host\” or \”shell\”) can consume.\n* Webpack Module Federation allows you to expose parts of your Flutter web build as JavaScript modules that can be dynamically loaded and used by the Angular app.\n\n**2. Webpack Configuration for the Flutter Web App (Remote)**\n\n* **Key Configuration:**\n * **`name`**: A unique name for your Flutter web app module (e.g., `\”flutter_feature\”`).\n * **`exposes`**: Defines which parts of your Flutter web app should be exposed. This is the tricky part because you\’ll need to expose a JavaScript entry point that bootstraps the Flutter application within a given container.\n\n* **Webpack Example (Illustrative – requires adaptation based on your Flutter build output):**\n\n “`javascript\n // webpack.config.js (Flutter Web App)\n const path = require(\’path\’);\n const { ModuleFederationPlugin } = require(\’webpack\’).container;\n\n module.exports = {\n entry: \’./lib/web_entrypoint.dart.js\’, // Path to your Flutter web\’s main.dart.js file. This is CRUCIAL.\n output: {\n path: path.resolve(__dirname, \’dist\’), // Output directory for the build\n publicPath: \’http://localhost:4001/\’, // Important: The URL where the remote module will be served. Adjust as needed.\n filename: \’remoteEntry.js\’, //This name is configurable\n chunkFilename: \'[id].[contenthash].js\’\n },\n devServer: {\n port: 4001, // Port for the Flutter micro frontend\n headers: {\n \”Access-Control-Allow-Origin\”: \”*\”,\n \”Access-Control-Allow-Methods\”: \”GET, POST, PUT, DELETE, PATCH, OPTIONS\”,\n \”Access-Control-Allow-Headers\”: \”X-Requested-With, content-type, Authorization\”\n }\n },\n module: {\n rules: [\n {\n test: /\\.js$/,\n use: {\n loader: \’babel-loader\’, // Consider Babel for compatibility\n options: {\n presets: [\’@babel/preset-env\’]\n }\n }\n },\n {\n test: /\\.css$/i,\n use: [\”style-loader\”, \”css-loader\”],\n },\n {\n test: /\\.(png|svg|jpg|jpeg|gif)$/i,\n type: \’asset/resource\’,\n },\n ]\n },\n plugins: [\n new ModuleFederationPlugin({\n name: \’flutter_feature\’,\n filename: \’remoteEntry.js\’,\n exposes: {\n \’./FlutterWidget\’: \’./lib/web_entrypoint.dart.js\’, //Exposing the flutter entry point\n },\n shared: [], // Define any shared dependencies (see below)\n }),\n ],\n };\n “`\n\n * **Important Notes:**\n * **`entry`**: This *must* point to the main JavaScript file generated by Flutter\’s web build (usually `main.dart.js` or something similar in the `lib` folder).\n * **`publicPath`**: This is critical. It tells Webpack where the remote module will be served from. Make sure this matches the URL of your development server (or the production URL if deployed).\n * **`exposes`**: This defines the module name (`./FlutterWidget` in the example) that your Angular application will use to import the Flutter component. The value associated with it points to the entry point.\n * **`shared`**: Handle shared dependencies carefully (see section on shared dependencies below).\n\n**3. Webpack Configuration for the Angular Application (Host)**\n\n* **Key Configuration:**\n * **`remotes`**: Specifies the location of the remote module (your Flutter web app).\n\n* **Webpack Example (Illustrative):**\n\n “`javascript\n // webpack.config.js (Angular App)\n const ModuleFederationPlugin = require(\’webpack/lib/container/ModuleFederationPlugin\’);\n const mf = require(\’@angular-architects/module-federation/webpack\’);\n const path = require(\’path\’);\n\n const share = mf.share;\n\n module.exports = {\n output: {\n uniqueName: \”angular_shell\”,\n publicPath: \”auto\”,\n path: path.resolve(__dirname, \’dist\’)\n },\n optimization: {\n runtimeChunk: false\n },\n resolve: {\n alias: {\n …share({\n \”@angular/core\”: { requiredVersion: \’auto\’ },\n \”@angular/common\”: { requiredVersion: \’auto\’ },\n \”@angular/common/http\”: { requiredVersion: \’auto\’ },\n \”@angular/router\”: { requiredVersion: \’auto\’ },\n \”rxjs\”: { requiredVersion: \’auto\’ },\n \”@angular/platform-browser\”: { requiredVersion: \’auto\’ },\n \”@angular/platform-browser-dynamic\”: { requiredVersion: \’auto\’ },\n })\n },\n },\n experiments: {\n outputModule: true,\n },\n plugins: [\n new ModuleFederationPlugin({\n name: \”angular_shell\”,\n filename: \”remoteEntry.js\”,\n exposes: {\n },\n remotes: {\n \”flutter_feature\”: \”flutter_feature@http://localhost:4001/remoteEntry.js\” //Important\n },\n shared: share({\n \”@angular/core\”: { singleton: true, strictVersion: false, requiredVersion: \’auto\’ },\n \”@angular/common\”: { singleton: true, strictVersion: false, requiredVersion: \’auto\’ },\n \”@angular/common/http\”: { singleton: true, strictVersion: false, requiredVersion: \’auto\’ },\n \”@angular/router\”: { singleton: true, strictVersion: false, requiredVersion: \’auto\’ },\n \”rxjs\”: { singleton: true, strictVersion: false, requiredVersion: \’auto\’ },\n \”@angular/platform-browser\”: { singleton: true, strictVersion: false, requiredVersion: \’auto\’ },\n \”@angular/platform-browser-dynamic\”: { singleton: true, strictVersion: false, requiredVersion: \’auto\’ },\n })\n })\n ],\n };\n “`\n\n * **Important Notes:**\n * **`remotes`**: This is where you tell Angular how to find your Flutter web app. The key `\”flutter_feature\”` is the name you gave the remote module in the Flutter\’s Webpack config. The value `\”flutter_feature@http://localhost:4001/remoteEntry.js\”` specifies the module name and the URL to the `remoteEntry.js` file. Adjust the URL to match where your Flutter app is served.\n * **`shared`**: Carefully configure shared dependencies (see below). The example shows how to share Angular-related dependencies.\n\n**4. Loading the Flutter Micro Frontend in Angular**\n\n* **Dynamic Import:** In your Angular component, use a dynamic import to load the Flutter module.\n\n “`typescript\n // my-angular-component.ts\n import { Component, OnInit, AfterViewInit, ElementRef, ViewChild } from \’@angular/core\’;\n\n @Component({\n selector: \’app-my-angular-component\’,\n template: \’
\’, // Container to hold the Flutter app\n })\n export class MyAngularComponent implements OnInit, AfterViewInit {\n @ViewChild(\’flutterContainer\’, { static: false }) flutterContainer!: ElementRef;\n\n async ngAfterViewInit() {\n try {\n const flutterApp = await import(\’flutter_feature/FlutterWidget\’); //Import the remote module\n\n // Access the Flutter\’s bootstrap function (adjust as needed)\n flutterApp.default.then((value: any) => {\n value.bootstrap({\n target: this.flutterContainer.nativeElement,\n config: {\n // Add any necessary configuration here\n }\n })\n });\n\n } catch (error) {\n console.error(\’Error loading Flutter module:\’, error);\n }\n }\n\n ngOnInit(): void {\n }\n }\n “`\n\n * **Explanation:**\n * `import(\’flutter_feature/FlutterWidget\’)`: This dynamically imports the Flutter module you exposed in your Flutter\’s Webpack config. `flutter_feature` is the remote name, and `FlutterWidget` is the exposed module name.\n * **Container:** Create a `
`) to act as the container where the Flutter app will be rendered.\n * `this.flutterContainer.nativeElement`: Get a reference to the container element.\n * **Flutter bootstrap:** The imported module should contain the bootstrap code for rendering your Flutter Web app within the container. You may need to adapt this part based on how Flutter exposes its entry point. The code example assumes that the exposed module is a promise which has a `bootstrap` method.\n* **Angular Routing:** Set up an Angular route to display this component when the user navigates to the desired URL.\n\n**5. Handling Shared Dependencies**\n\n* **Crucial Importance:** Webpack Module Federation allows you to share dependencies between the host (Angular) and the remote (Flutter). This prevents loading multiple copies of the same library.\n* **Configuration:** Use the `shared` property in both the Angular and Flutter Webpack configurations to declare shared dependencies.\n* **Example (Illustrative):**\n\n “`javascript\n // In both Angular and Flutter webpack.config.js:\n shared: {\n // Example: Share React if Flutter uses it (unlikely in a pure Flutter web app)\n // \”react\”: { singleton: true, requiredVersion: \’^17.0.0\’ },\n //If Flutter and Angular both use a common library\n // \”lodash\”: {singleton: true, requiredVersion: \’^4.0.0\’}\n }\n “`\n\n * **`singleton: true`**: Ensures only one instance of the shared dependency is loaded.\n * **`requiredVersion`**: Specifies the version range of the dependency that is compatible. Use `\’auto\’` where possible to let Module Federation resolve the correct version.\n* **Challenges:** Flutter web apps often have their own internal dependency management. You may not be able to share *everything*. Focus on sharing dependencies that both Angular and Flutter explicitly use (e.g., a utility library).\n\n**6. Addressing Potential Problems and Challenges**\n\n* **Flutter\’s Build Process:** Flutter\’s web build generates a complex JavaScript bundle. You\’ll need to carefully inspect the output to identify the correct entry point to expose.\n* **CSS Conflicts:** CSS styles from the Flutter web app might conflict with Angular\’s styles. Consider using CSS Modules or a CSS-in-JS solution to isolate styles.\n* **Routing Conflicts:** Make sure the Angular router handles the overall application routing. Avoid overlapping routes between Angular and Flutter.\n* **Communication:** If you need to pass data between Angular and Flutter, consider using:\n * **Custom Events:** Dispatch custom DOM events from one framework and listen for them in the other.\n * **Shared State Management (with caution):** Libraries like RxJS BehaviorSubjects could be used to share simple state, but be aware of the complexity this adds.\n* **Performance:** Loading a large Flutter web app as a micro frontend can impact initial load time. Optimize your Flutter web build for performance. Code splitting is recommended.\n* **CORS:** If your Angular and Flutter apps are served from different origins, you\’ll need to configure CORS headers on the Flutter server to allow requests from the Angular origin. The `devServer` configuration in the Flutter Webpack example includes CORS headers for development.\n* **Development Workflow:** Setting up a smooth development workflow can be challenging. Consider using tools like `concurrently` or `npm-run-all` to run both the Angular and Flutter development servers simultaneously.\n\n**7. Alternative Approaches (If Module Federation Proves Too Complex)**\n\n* **IFrames:** The simplest approach is to embed the Flutter web app in an `