enable async in formatError hook

[anymost]

[feature] enable async in formatError hook
https://github.com/apollographql/apollo-server/issues/1747

[apollo-cla]

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[martijnwalraven]

Can you explain in more detail why you need the ability for formatError to run asynchronously? As this function is in the critical path for generating a response, it should return as fast as possible. And I have trouble thinking of use cases that would require async behavior for formatting.

[anymost]

@martijnwalraven Hi，The reason why I use async/await in formatError is we have so internal tools. The tools are used to report error and so on, But most tools are run async asynchronously, so I want to formatError support asynchronous logic.

[anymost]

meantime, formatResponse hook support async/await, I take formatError hook supporting async/await for granted

[eltonio450]

@martijnwalraven we also use async function to log errors (via Sentry), and would like to use the formatError hook to do so.

Do you think this PR is going to be merged in master in the future ?

thank you !!

[eltonio450]

(to be even more specific, we use the serverless version of apollo server, and everything needs to be handled before the return. For now, we receive empty errors + erros are not reported in sentry

[abernix]

Thanks for opening this originally.

As of #2719 (which is included in the latest alpha releases of Apollo Server 2.6.0 on the next npm dist-tag; tracked in #2669) we now include a didEncounterErrors life-cycle hook as part of the request pipeline events. It supports async so should hopefully be exactly what you need in order to implement this and cover this use-case. Please let us know if this doesn't tick that box!