Reset error when request succeeds

[8enSmith]

This is a fix for the issue "error is not reset if subsequent request succeeds".

Pretty sure this is the correct fix but please review!

[simoneb]

Thanks for this @8enSmith. I think this works fine but I'm not sure about the semantics. I can see two options, you have implemented the first:

1. we reset the previous error as soon as we start the next request
2. we reset the error only once we receive a successful response

I guess both would make sense, and I'm wondering if we should go for the first or the second, I think both have pros and cons.

[8enSmith]

@simoneb yes I agree that those are the two scenarios. However if a request fails and a refetch is triggered the previous error is redundant as it is only relevant to the previous failed request. When the refetch is triggered the error for that specific operation should be initialised to null as this is a new request.

Generally I think it is a better approach to keep updating the value of error after each request's response as opposed to keeping it set for historical failures.

That is my take on this anyhow!

[simoneb]

@8enSmith good argument. approved