Dynamic Remote Module Loading in Angular

Imagine you're building a large, modular Angular application. You want to load certain parts of your application on demand, rather than bundling everything together initially. This challenge focuses on implementing a system where "remote" Angular applications can be dynamically loaded into a "host" application at runtime. This is a powerful pattern for micro-frontends, allowing for independent development, deployment, and scaling of application modules.

Problem Description

Your task is to create a mechanism within an Angular application (the "host") that allows it to dynamically load another Angular application (a "remote") as a module. This means the host application should be able to discover, fetch, and render components from the remote application without them being part of the initial host build.

Key Requirements:

1. Host Application: The host application will have a dedicated area or mechanism to trigger the loading of a remote module.
2. Remote Application: A separate Angular application designed to be loadable by the host. It should expose specific components or entry points that the host can interact with.
3. Dynamic Loading: The host must be able to fetch and instantiate components from the remote module at runtime, typically based on user interaction or application state.
4. Module Federation: You should leverage Angular's module federation capabilities (or a similar concept if using an alternative setup like Nx) to achieve this dynamic loading. For this challenge, assume a setup akin to Webpack Module Federation is available.
5. Component Rendering: The host should be able to render a component from the loaded remote module within its own DOM.

Expected Behavior:

The host application should present a UI element (e.g., a button). When this element is interacted with, the host will:

• Fetch the remote module.
• Instantiate a specific component from the remote module.
• Render that component into a designated placeholder in the host's UI.

Edge Cases:

• Remote Module Not Found/Failed to Load: The host should gracefully handle scenarios where the remote module cannot be fetched (e.g., network error, incorrect URL).
• Remote Component Not Found: If the requested component within the remote module doesn't exist, the host should report an error or display a fallback.
• Multiple Remotes: The system should be extensible to load multiple different remote modules.

Examples

Example 1: Basic Remote Loading

• Host Application: Has a button labeled "Load Remote Feature". A div with id="remote-container" exists in the HTML.
• Remote Application (e.g., remote-feature): Exposes a component FeatureComponent which displays "Hello from Remote Feature!".

Interaction:

1. User clicks "Load Remote Feature".
2. Host application fetches the remote-feature module.
3. Host application instantiates FeatureComponent from remote-feature.
4. The output of FeatureComponent is rendered inside #remote-container.

Output (inside #remote-container):

Hello from Remote Feature!

Example 2: Loading Different Remotes

• Host Application: Has two buttons: "Load Feature A" and "Load Feature B".
• Remote Application A (e.g., remote-a): Exposes ComponentA which displays "Content from Remote A".
• Remote Application B (e.g., remote-b): Exposes ComponentB which displays "Content from Remote B".

Interaction:

1. User clicks "Load Feature A". ComponentA is rendered in a placeholder.
2. User clicks "Load Feature B". ComponentB is rendered in the same placeholder (or a different one, depending on implementation).

Output (after loading Feature B):

Content from Remote B

Example 3: Error Handling

• Host Application: Has a button "Load Non-existent Feature".
• Scenario: The non-existent-feature remote is misconfigured or not deployed.

Interaction:

1. User clicks "Load Non-existent Feature".
2. Host application attempts to fetch the non-existent-feature module but fails.

Expected Behavior: The host application should display an error message like "Failed to load remote feature." or log an error to the console, without crashing.

Constraints

• Technology: Angular (version 13+ recommended for robust module federation support), TypeScript.
• Module Federation: Assume a Webpack Module Federation setup or equivalent (like Nx's remote/module federation setup) is configured for both host and remote applications.
• Entry Point: Each remote module will expose a clearly defined entry point (e.g., a specific component or a factory function).
• Performance: The initial load of the host application should not be significantly impacted by the potential to load remotes. Remotes should only be fetched when explicitly requested.

Notes

• This challenge is designed to test your understanding of how to integrate separate Angular applications dynamically.
• Focus on the host's responsibility in discovering, loading, and rendering remote components.
• Consider how you would pass data between the host and the remote component (though explicit implementation of complex data passing is not the primary focus, acknowledge its importance).
• Think about how to manage the lifecycle of remote components.
• The actual configuration of Webpack Module Federation or Nx for setting up module-federation.config.ts and related files is assumed to be handled. Your focus is on the Angular application logic that consumes these remotes.