Swift Concurrency Support

[NeedleInAJayStack]

This adds support for Swift concurrency by adding new top-level async public APIs.

It also adds a Swift concurrency-based EventStream. This allows us to directly test the subscription functionality within this package, and allows clients to use GraphQL subscriptions without coding custom EventStreams (which typically required drivers like GraphQLRxSwift)

Long term, we probably want to remove the EventStream workaround and just use the swift concurrency types by default. This has been left as a future task though, because it would require a breaking API change and require all clients to be using swift versions that support concurrency.

[paulofaria]

Hey, J! This all looks great. Thank you for finally looking into async/await support. I'm really out of time these days. If you have some time, it would be nice if you took a look at the work I have in GraphQLSwift/Graphiti#71. Besides async/await, it also adds support for client and server directives, which I think it's pretty neat. To implement it, I had to do some work here, which is in the same branch name feature/async-await. One issue I had was with the visitor/reducer. I see there is some outstanding PRs working on something related? If you're interested, would be nice to consolidate all of these efforts. Take a look at the branches and let me know what you think. I also had some ideas about improving the API and bring it much closer to the GraphQL SDL, but those would be mostly cosmetic, so we can postpone that, for sure.

[paulofaria]

Basically you define a directive like this:

https://github.com/GraphQLSwift/Graphiti/blob/50f4ae95b15d217454d4b8f1ef189be7ade129b3/Tests/GraphitiTests/CounterTests/CounterTests.swift#L196-L226

Then you add it to the schema like this:

https://github.com/GraphQLSwift/Graphiti/blob/50f4ae95b15d217454d4b8f1ef189be7ade129b3/Tests/GraphitiTests/CounterTests/CounterTests.swift#L270-L273

Then you apply to a field, for example, like this:

https://github.com/GraphQLSwift/Graphiti/blob/50f4ae95b15d217454d4b8f1ef189be7ade129b3/Tests/GraphitiTests/CounterTests/CounterTests.swift#L282

[paulofaria]

If you have no interest in looking into that, that's cool too. 😄

[paulofaria]

By the way, feel free to merge the PR and tag a new release. 😊

[NeedleInAJayStack]

Oh woah, adding directives like that looks awesome!! I'll have a look over the next week or two for sure!

[d-exclaimation]

Sorry to suddenly jump here. I was planning to add support to the new ConcurrentEventStream to my library, Pioneer, but I found some issues with the current implementation of .mapStream, which I explained in #101. I have proposed a solution for it in #102 but it needs to be reviewed.

[NeedleInAJayStack]

No need to be sorry at all, @d-exclaimation. This work was my first foray into Swift async/await, so I'm glad to have someone watching my back 😄. I'll jump on and review for sure.