TypeScript custom declaration files for untyped npm modules

Question

I am consuming a React component called shiitake from npm into my project where I use TypeScript. That library does not have TypeScript declarations so I thought I would write one. The declaration file looks like below (it may not be complete but don't worry about it too much):

import * as React from 'react';

declare module 'shiitake' {

    export interface ShiitakeProps {
        lines: number;
    }

    export default class Shiitake extends React.Component<ShiitakeProps, any> { 
    }
}

I have put this inside ./typings/shiitake.d.ts file and on VS Code, I am seeing the below error:

[ts] Invalid module name in augmentation. Module 'shiitake' resolves to an untyped module at 'd:/dev/foo/foobar.foo.Client.Web/node_modules/shiitake/dist/index.js', which cannot be augmented.

On the consumption side, I am still getting the same error even if with the above declaration (since I have noImplicitAny compiler switch turned on):

/// <reference path="../../../../typings/shiitake.d.ts" />
import * as React from 'react';
import Shiitake from 'shiitake';

[ts] Could not find a declaration file for module 'shiitake'. 'd:/dev/foo/foobar.foo.Client.Web/node_modules/shiitake/dist/index.js' implicitly has an 'any' type.

The standard why of acquiring declaration files for this type of modules is through @types/ way and it works well. However, I cannot get the custom typings work. Any thoughts?

Answer 1

The declaration declare module 'shiitake'; should be in a global scope. i.e. a top-level declaration in a non-module (where a module is a file with at least one top-level import or export).

A declaration of the form declare module '...' { } in a module is an augmentation. For more details see Typescript Module Augmentation.

So you want this file to look like this:

declare module 'shiitake' {

    import * as React from 'react';

    export interface ShiitakeProps {
        lines: number;
    }

    export default class Shiitake extends React.Component<ShiitakeProps, any> { 
    }
}