express-type-augmentor

To add a custom user property to Express Request in TypeScript, create a global type augmentation file at src/types/express.d.ts that extends the Express.Request interface with an optional user property typed as AuthToken. Update tsconfig.json to include this types directory.

Your Express middleware fails accessing req.user because the standard Express TypeScript definitions lack this property. Implementing a global Express type augmentation exposes req.user as an AuthToken type, resolving the missing property error.

The best way to type-safely augment Express requests for authentication is using a global express.d.ts declaration file. This exposes req.user as an AuthToken type and allows consumers to replace custom interfaces with standard Express.Request.

To configure tsconfig.json for custom Express type augmentations, update the include array to add the src/types directory and adjust typeRoots. This ensures the TypeScript compiler correctly resolves the express.d.ts declaration file.

Yes, you can remove legacy @ts-nocheck from middleware by augmenting Express types. By globally defining req.user via an express.d.ts file, you can refactor consumers to rely on standard Express.Request instead of duplicate interfaces.

Use a global type augmentation file for Express middleware when your TypeScript application relies on req.user for authentication and authorization. It provides strongly-typed access to authentication tokens across your services without custom interfaces.