Replace `new Promise` and `.then` with async/await

[harrysarson]

We no longer support node 8 so there is nothing holding us back from asyncing and awaiting.

---

To do this

1. Search in files for new Promise or .then.
2. Replace it with an async function.
3. Make a PR.

It is worth keeping the PR's small (maybe only adding a one or two async/awaits at a time) so we can review them quickly and get them merged!

[chebro]

Hi, I'd like to contribute!

[harrysarson]

Hi! Go for it!

[chebro]

I haven't worked with .then() blocks in a return statements a lot, it would be awesome if you could help me out here! I'm looking at this bit of code:

      return Parser.extractExposedPossiblyTests(filePath).then(
        (possiblyTests) => ({
          moduleName,
          possiblyTests,
        })
      );

I don't understand how to return a Promise.then(), using await, what I could think of is this

      possiblyTests = await Parser.extractExposedPossiblyTests(filePath)
      return (possiblyTests) => ({
          moduleName,
          possiblyTests,
        })

This will simply wait for the Promise to resolve and return the function that follows. But I'm assuming we have to return the Promise as it is and let the code that called this function that called it handle the waiting, or am I wrong?

[harrysarson]

So the trick it to make the function async so

function xxx(args) {
      ...
      return Parser.extractExposedPossiblyTests(filePath).then(
        (possiblyTests) => ({
          moduleName,
          possiblyTests,
        })
      );
}

becomes

async function xxx(args) {
      ...
      const possiblyTests = await Parser.extractExposedPossiblyTests(filePath);
      return {
          moduleName,
          possiblyTests,
      };
}

and because it is an async function it will return a promise exactly the same as before.

[chebro]

So the trick it to make the function async

Yes! That's given, as the await is only valid when the function is async, I wanted to know if we are return-ing resolved promises or not. Thanks this helps, I'll make some PRs in the morning :)