Global type definition problem

[mb-tousif]

If I declare any custom type in express, typescript project in some where in ./src it does not work. like
in index.d.ts

import { JwtPayload } from 'jsonwebtoken';

declare global {
  namespace Express {
    interface Request {
      user: JwtPayload | null;
    }
  }
}

But When I on top of my middleware file like

import { JwtPayload } from 'jsonwebtoken';

declare global {
  namespace Express {
    interface Request {
      user: JwtPayload | null;
    }
  }
}

const Auth = ()=>{

// SOME Fun

}
export default Auth.

it works.

Please let me know is it ts-node problem or not? and how can I get better solution.

[agammann]

The augmentation itself is valid. A likely cause is that ts-node has not loaded your separate index.d.ts: by default it starts from the entry script and its imports/references, rather than eagerly loading every file listed by include.

Keep your declaration in src/index.d.ts, make sure it is included in your project, and enable ts-node's files option:

{
  "compilerOptions": {
    "module": "CommonJS",
    "strict": true
  },
  "include": ["src/**/*.ts", "src/**/*.d.ts"],
  "ts-node": {
    "files": true
  }
}

Or test the change from the CLI without editing the config:

npx ts-node --files src/middleware.ts

The top-level import in your .d.ts already makes it a module, which is required for declare global. Do not import the .d.ts as a normal runtime module.

I reproduced a missing Request['user'] error with the separate declaration, then both --files and the config option made it type check and run (ts-node 10.9.2, TypeScript 5.9.3). See Missing Types.