JSDoc type annotations on module.exports assignments not type checked

[jpage-godaddy]

🔍 Search Terms

jsdoc module.exports 

✅ Viability Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

Adding a @type JSDoc annotation to module.exports should type check like it does in other contexts.

📃 Motivating Example

Currently, given the following blah/some-type.ts:

export default interface SomeType {
  name: string,
  age: number
}

...this doesn't type check:

/** @type {import('./blah/some-type').default} */
module.exports = {
  name: 0,
  age: 'forty-three'
};

...but this does, with some extra steps:

/** @type {import('./blah/some-type').default} */
const obj = {
  name: 0,
  age: 'forty-three'
};

module.exports = obj;

This is similar to #27327, but a simple thing like adding a @type {string} to module.exports does work. An imported type does not.

💻 Use Cases

We have a CommonJS JS config file that we'd like to enable users to type check. The expected way you'd think you'd add a type annotation to it doesn't work.

[aaronadamsCA]

I've run into the same problem with different details.

On TypeScript 4.9.5, typing module.exports with an imported type is fine - as long as the file does not include JSX syntax.

This gatsby-browser.jsx type checks:

/** @type {import("gatsby").GatsbyBrowser} */
module.exports = {
  shouldUpdateScroll: ({ routerProps }) =>
    routerProps.location.state?.shouldUpdateScroll ?? true,
};

This one does not:

const { RouteUpdateProgress } = require("./src/components/RouteUpdateProgress");

/** @type {import("gatsby").GatsbyBrowser} */
module.exports = {
  shouldUpdateScroll: ({ routerProps }) => // Binding element 'routerProps' implicitly has an 'any' type.
    routerProps.location.state?.shouldUpdateScroll ?? true,
  wrapPageElement: ({ element }) => ( // Binding element 'element' implicitly has an 'any' type.
    <RouteUpdateProgress>{element}</RouteUpdateProgress>
  ),
};

Workaround is same as OP.

[karlhorky]

Ah looks like this issue is also similar to (or maybe even the same as) my issue over here:

• JSDoc: module.exports direct literal assignment not type checked #51819