[TypeScript] Omit `undefined` from return type if `defaultValue` is specified

[acro5piano]

Hi! First of all, thank you for the amazing library.

I found env.get('env', 'default') returns string | undefined which is not possible, because it always returns string.

This can be fixed by using Overload signature like this:

// dist/env.d.ts

export class Env {
    get(key: string): string | undefined;
    get(key: string, defaultValue: string): string;
}

I took a look at the code and possible solutions are the following.

• Re-write code in TypeScript
• Create the TypeScript declaration file manually

Can I send a PR for this? If so, which solution do you prefer?

Best regards,

[nzakas]

Thanks, I'm not interested in maintaining a separate TypeScript definition file or converting the project to TypeScript. If there's a way to do it just with JavaScript and JSDoc, then I'm happy to consider it.

[acro5piano]

Thank you for your reply.

If there's a way to do it just with JavaScript and JSDoc, then I'm happy to consider it.

I searched about JSDoc, but I don't think there is the way to express overload signature.

I'm not interested in maintaining a separate TypeScript definition file or converting the project to TypeScript

Then, the only way is to create a separate method for this, like

const username = env.ensure('USERNAME', 'defaultValue')

// `username` is always string

Or modify the generated declaration file by running some script, but this is a too ugly solution.

[nzakas]

Yeah, I didn’t think there was a way to do it, but thanks for investigating.