Fixing Lazy-loaded Angular Modules with @ nguniversal for Server-Side Rendering

Learn how to resolve issues with `lazy-loaded Angular modules` not rendering correctly in your `@ nguniversal` setup for efficient server-side rendering.
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This video is based on the question stackoverflow.com/q/66522000/ asked by the user 'Martin Sotirov' ( stackoverflow.com/u/1575782/ ) and on the answer stackoverflow.com/a/66536910/ provided by the user 'Martin Sotirov' ( stackoverflow.com/u/1575782/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting Lazy-loaded Angular Modules with @ nguniversal

When working with Angular applications, especially with the implementation of server-side rendering (SSR) using @ nguniversal, developers may encounter a variety of issues. One common issue is when lazy-loaded Angular modules do not render properly on the server side, leading to unexpected 404 errors or even blank pages. In this post, we will explore why this happens and how to resolve these issues effectively.

The Issue at Hand

Recently, a developer noticed that after restructuring an Angular 11 application to use lazy-loaded modules, the SSR functionality became problematic. Even though client-side routing and rendering worked seamlessly, some URLs were either leading to 404 errors or were rendering blank pages—containing nothing but an empty <router-outlet>. This inconsistency indicates a significant breakdown in how the server processes requests for lazy-loaded content.

Brief Examination of Router Configuration

The developer’s routing might look something like this:

[[See Video to Reveal this Text or Code Snippet]]

This structure suggests normal behavior for implementing lazy loading, but the issue lies in how the server is handling these routes.

Discovering the Root Cause

Upon a deeper look, the developer found that @ nguniversal was stripping trailing slashes from URLs, leading to mismatched routing behavior. This problem can lead to inconsistencies, such as the server interpreting routes incorrectly, which is especially prevalent when using Angular's standard routing approaches.

A Solution for Trailing Slashes

To resolve this problem, a custom UrlSerializer can be created to handle the trailing slashes correctly without requiring users to modify router configurations or individual router links.

Custom UrlSerializer Implementation

Here is how you can create a TrailingSlashSerializer:

[[See Video to Reveal this Text or Code Snippet]]

This class alters the way URLs are parsed and serialized by adding and processing trailing slashes appropriately.

Registering the Serializer

Next, include the serializer in your app module's providers:

[[See Video to Reveal this Text or Code Snippet]]

This setup ensures that Angular uses your custom serializer instead of the default one, allowing for correct handling of URLs with trailing slashes across the application, thus resolving the routing issues.

Conclusion

With the @ nguniversal and Angular SSR, handling lazy-loaded modules correctly can save a lot of headaches. By implementing a custom UrlSerializer, you ensure that your application behaves consistently for both server-side and client-side routes, resolving issues that lead to 404 errors or blank pages.

Feel free to implement this solution in your own projects and watch as the frustrating issues vanish!