feat: support async custom functions

[P0lip]

Closes #694

Checklist

• Tests added / updated
• Docs added / updated

Does this PR introduce a breaking change?

• Yes
• No

[philsturgeon]

Yeah, let’s show off our features!

…

On Fri, Apr 10, 2020 at 16:35, Jakub Rożek ***@***.***> wrote: @P0lip commented on this pull request. --------------------------------------------------------------- In [docs/guides/custom-functions.md](#1058 (comment)): > @@ -2,6 +2,10 @@ If the built-in functions are not enough for your [custom ruleset](../getting-started/rulesets.md), Spectral allows you to write and use your own custom functions. +As of Spectral 5.4.0, custom functions can also be asynchronous. +Be aware that linting should be deterministic. That being said, please refrain from introducing any logic that is prone to non-deterministic behavior, i.e. contacting external service you have no control of, and hence cannot predict the response. > This could be a warning block. Do you mean the warning block from SMD? — You are receiving this because you commented. Reply to this email directly, [view it on GitHub](#1058 (comment)), or [unsubscribe](https://github.com/notifications/unsubscribe-auth/AAAQONIWITQ7XSMYHODQTJTRL44F3ANCNFSM4MBPPGHQ).

[nulltoken]

@P0lip What's the effect from throwing from within a function? Does the whole process crash down? Do we get a special kind of result or a console log?

From the function writer standpoint, what kind of code should be written

• if I don't want this failure being unnoticed
• if I prefer to see a CI build fail rather than having it pass for the wrong reasons

Note: I know this is kind off-topic with regards to the scope of the PR but... well... this is documentation and, to be honest, the doco actually lacks guidance about this.

Note 2: If you prefer this to be dealt with later, could you please log an issue to keep track of that?

[P0lip]

@P0lip What's the effect from throwing from within a function? Does the whole process crash down? Do we get a special kind of result or a console log?

We'd get a console.log, same as we do when any other custom function throws an exception.
The whole process would still keep on going.

if I prefer to see a CI build fail rather than having it pass for the wrong reasons

I'd return a regular error, i.e.

return [{ message: 'Network error. The check could not be performed' }]

[nulltoken]

@P0lip That's very valuable info. I've logged #1096 as I think this deserves a doco section of its own.

[philsturgeon]

This is so great!