CODEWITHSUNDEEP
typescriptdeclaration
Sandy Gifford
Sandy Gifford

Reputation: 8136

Untyped module for function top-level export with properties

I'm trying to write a typings file for changeset. I'm keeping it internal to my own project (this may be relevant later). Changeset has two use cases:

import * as changeset from "changeset";

changeset({}, {}); // call as function
changeset.applyChanges({}, {}); // call a property on changeset

the actual function in changeset is called apply, not applyChanges. I've changed it here to avoid confusion with Javascript's built in apply method.

To accomplish this I've set up the above file (index.ts), and changeset.d.ts

declare function changeset(objA: any, objB: any): any;
declare module "changeset" {
    export function applyChanges(changes: any, obj: any): any;
}

changeset.applyChanges(...) works correctly, changeset(...) does not:

This expression is not callable.
  Type 'typeof import("changeset")' has no call signatures.

My .d.ts is very similar to TypeScript's suggestion, only missing export = changeset; at the bottom. I don't fully understand why, but adding the export causes the import in index.ts to error out:

Could not find a declaration file for module 'changeset'.

As far as I can guess, the difference is that other .d.ts files are imported from node_modules whereas this one is implicately part of my project.

Is there any way to include complex module declarations like this in a single project?

EDIT

Tried a different way:

declare module "changeset" {
    const changeset: {
        (objA: any, objB: any): any;
        applyChanges: (changes: any, obj: any) => any;
    };
    export = changeset;
}

Same error as before: changeset.applyChanges(...) works correctly, changeset(...) does not...

Upvotes: 0

Views: 200

Answers (1)

Alex Wayne
Alex Wayne

Reputation: 186984

I think your type is fine, but if the changeset module has a default export (the main function, with properties on it that are also functions), you probably want to import it like so:

import changeset from "changeset";

Upvotes: 1

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