TS2669

error TS2669: Augmentations for the global scope can only be directly nested in external modules or ambient module declarations.

Solution

Broken Code ❌

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declare global {
  namespace NodeJS {
    interface Global {
      __coverage__: {};
    }
  }
}

You have to turn your code into a module by adding an import or export statement to your code. The easiest way to solve the problem is exporting an empty object:

Fixed Code ✔️

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declare global {
  namespace NodeJS {
    interface Global {
      __coverage__: {};
    }
  }
}

export {}