How to Properly Implement a NestJS Guard with GraphQL

Learn how to successfully integrate NestJS guards with GraphQL resolvers. Understand common pitfalls and see practical solutions to ensure proper authentication.
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How to Properly Implement a NestJS Guard with GraphQL

In the world of web development, ensuring that your applications are secure is a top priority. When working with NestJS and GraphQL, you often need to implement guards to protect your resolvers and manage authentication. However, you might run into issues where your guards don’t seem to work as expected. In this post, we'll explore a common problem with implementing authentication guards in a GraphQL resolver and how to solve it effectively.

The Problem: Guard Not Triggering

When trying to add an authentication guard to a GraphQL resolver, you may find that your canActivate method is not firing as anticipated. Take a look at the following simple guard implementation:

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

This guard is designed to reject all requests, but it doesn't appear to be invoked in a GraphQL resolver:

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

While this guard works as intended in an HTTP controller, it fails in the context of GraphQL resolvers.

Why the Guard Fails

The core issue lies in the configuration of the AppModule. When you included the RecipeResolver in the imports array instead of the providers array, NestJS did not set up the request lifecycle properly for guards to function in a GraphQL context. Guards need to be able to resolve dependencies and lifecycle hooks correctly, which requires them to be registered appropriately.

The Solution

Now that we’ve identified the issue, let's fix it.

Step 1: Move the Resolver to the Providers Array

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

Step 2: Check Guard Usage

After moving the resolver, your guard implementation using @ UseGuards(AuthGuard) should now work properly. It will utilize the NestJS dependency injection system correctly, allowing your guard's canActivate method to execute as intended.

Additional Tips

If you encounter further issues, ensure that your GraphQLModule is set up correctly and that all necessary providers are properly configured.

Always test your guards in different contexts (HTTP and GraphQL) to confirm their functionality in various parts of your application.

Conclusion

Implementing authentication in a NestJS GraphQL application might seem tricky at first, especially if your guards do not appear to trigger. However, by ensuring that your resolvers are correctly configured in the providers array, you can fully leverage NestJS’s powerful dependency injection system and lifecycle management. Keep these tips in mind when working with guards in your applications, and you’ll be well on your way to building secure and efficient GraphQL services.