[Docs] This argument as first parameter to step definition function

[Izhaki]

In #1667 (comment) the proposed solution by @davidjgoss is:

import {Then, World} from '@cucumber/cucumber';

Then('the test runs with string parameter {string}', async function(this: World, parameter: string) {
    this.driver.close()
})

I could not find any mention of this in the docs. Further, 20m of code surfing, and I couldn't even find where this is actually happening.

If this an official API? This changes things quite a bit as it unlocks the use of arrow functions.

We would like our world to be typed, and right now this is the only way to do this. So we need insurance this API is official.

[davidjgoss]

Hey @Izhaki, bit of a misunderstanding here. The context of that issue and my comment was TypeScript, which allows you to type this for a function by prepending it to the arguments - but it's not an actual argument and is compiled out. See https://www.typescriptlang.org/docs/handbook/2/functions.html#declaring-this-in-a-function. A quick playground to demo:

Unfortunately the limitation of arrow functions is unchanged. You might consider trying https://github.com/jbpros/cucumber-fp for an approach that skirts the this issue.

[davidjgoss]

We would like our world to be typed, and right now this is the only way to do this. So we need insurance this API is official.

To answer this specifically: yes if you're using TypeScript then whatever class you pass to setWorldConstructor you can use as the this arg on step/hook functions and you should get the type safety you need.

[Izhaki]

Awesome. Thanks!