[RFC-1] Generate typealias for Selection types

[maticzav]

It would be very beneficial if instead of having to write Selection<TypeLock, Target>, you could write SType<Target>. We can generate bindings for all the internal types since those are of finite set magnitude, and reduce the complexity drastically.

To showcase the idea, here's a rewritten example from our docs with the new implementation.

import SwiftGraphQL

// Define a Swift model.
struct Human: Identifiable {
    let id: String
    let name: String
    let homePlanet: String?
}

// Create a selection.
let human = SGHuman<Human> {
    Human(
        id: try $0.id(), 
        name: try $0.name(),
        homePlanet: try $0.homePlanet()
    )
}

// Construct a query.
let query = SGQuery<[Human]> {
    try $0.humans(human.list)
}

// Perform the query.
SG.send(query, to: "http://swift-graphql.heroku.com") { result in
    if let data = try? result.get() {
        print(data) // [Human]
    }
}

Open questions:

• What naming conventions do we want to follow to prevent naming collisions?

[Amzd]

You could make them children of Selection, it would not be that much shorter but you can use the dot syntax which autocompletes rather than the < & >. Another feature of this is that it can infer the return type from the closure.

Example with typealias on Selection:

// Create a selection.
let human = Selection.Human {
    Human(
        id: try $0.id(), 
        name: try $0.name(),
        homePlanet: try $0.homePlanet()
    )
}

// Construct a query.
let query = Selection.Query {
    try $0.humans(human.list)
}

To make this work we need to generate this:

extension Selection where TypeLock == Never, Type == Never {
    typealias Human<T> = Selection<T, Objects.Human>
    typealias Query<T> = Selection<T, Operations.Query>
}

[Amzd]

This is what I meant with autocomplete btw

[maticzav]

Yes, wonderful! I get it now. Will include it in the beta release.

Could you explain the benefit of having Type == Never at the top? Is there any difference if we just omit that part altogether?

[Amzd]

Not sure if it is related but in my test project without Never the autocompletion fails:

Without Never	Never

Screen.Recording.2021-02-03.at.14.50.41.mov

Which would make sense because it is unable to figure out the type of Selection

[Amzd]

To Add: it's basically saying the first Selection doesn't need it's Type and TypeLock. we specify it so the user doesn't have to type:

Selection<Never, Never>.Query

[maticzav]

This is great! Thanks!