Improve function return types

[mircea-pavel-anton]

What kind of change does this PR introduce?

What is the current behavior?

Fixes #55

Currently, the return type for most functions is:

Promise<{ data: { Key: string } | null; error: Error | null }>

Which means that a return type of either {null, null} or {{key: string}, Error} is technically possible even though it would not make any sense, so we have to manually check that data AND error are not null.

What is the new behavior?

By changing the return types to something like:

Promise<{ data: { Key: string }; error: null } | { data: null; error: Error }>

We basically narrow it down to data or error, not data and/or error as a possible return.
This also makes sure that we don't accidentally return {null, null}, for example, which would not have been reported as an error by typescript before.

Additional context

I also noticed that most of the try... catch blocks would show a warning because the error variable in catch (error) is not typed so it was reporting as unknown and unknown cannot be cast to either Error or null. As such, I also modified all try... catch statements to cast error as Error in the meantime. Eventually, some custom errors would be required, i think:

try {
...
} catch (error: any) {
  return { data: null, error } // no longer showing a warning for error being an unknown type
}

[alaister]

Hey @mirceanton,

Thanks for the PR! Unfortunately, it looks like we're working on the same problem simultaneously as there is already a PR open for this: #60.

I'm closing this in favour of #60, but I'd be very appreciative of any feedback you give over there!

[mircea-pavel-anton]

Oh, right. I didn't notice because the issue was not linked to the PR

[alaister]

Sorry about that - I've updated it.

[mircea-pavel-anton]

To be fair, the PR is pretty self descriptive in it's title :)) I guess I didn't really check already existing PRs as I noticed no linked ones