CODEWITHSUNDEEP
typescriptkoa-router
M. A.
M. A.

Reputation: 415

Add untyped JavaScript options property to declared class

I'm working with the koa-router type declarations from the DefinitelyTyped repository. The class declaration does not include a definition for the opts property, which means that attempting to access the property will produce a TS2339 error.

Aside from non-typed workarounds, e.g. (routerObj as any).opts.<option>, how can I add/extend this property with the types from IRouterOptions to the already existing definition?

*Edit*

I tried module augmentation, but I was unsuccessful in doing so:

import Router from 'koa-router';

declare module 'koa-router' {
  class Router {
    opts: Router.IRouterOptions
  }
}

And following the documentation bit above

import Router from 'koa-router';

declare module 'koa-router' {
  interface Router<T> {
    opts: Router.IRouterOptions
  }
}

Neither of these worked. The error message I get from VSCode is also quite strange, which leads me to believe TS treats my attempt on augmentation and the DefinitelyTyped definitions as independent definitions: Property 'opts' does not exist on type 'import("/Absolute/Path/To/node_modules/@types/koa-router/index.d.ts")'.

However, augmenting another interface from the DefinitelyTyped definitions does work:

import Router from 'koa-router';

declare module 'koa-router' {
  interface IRouterOptions {
    requiredVar: boolean;
  }
}

This will produce a TS2322: Type '{}' is not assignable to type 'IRouterOptions'. Property 'requiredVar' is missing in type '{}'.

Upvotes: 0

Views: 222

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