Operating and testing async Vapor instructions

The way to run async instructions in Vapor?

The async / await characteristic is comparatively new in Swift and a few framework authors have not transformed all the things to benefit from these new key phrases. At the moment, that is the state of affairs with the Command API in Vapor 4. You’ll be able to already outline async instructions, however there is not any technique to register them utilizing the Vapor framework. Thankfully, there’s a comparatively easy workaround that you should use if you wish to execute instructions utilizing an asynchronous context. 🔀

First we’ll outline a helper protocol and create an asyncRun operate. We’re going to prolong the unique Command protocol and supply a default implementation for the run methodology.

import Vapor

public protocol AsyncCommand: Command {
    
    func asyncRun(
        utilizing context: CommandContext,
        signature: Signature
    ) async throws
}

public extension AsyncCommand {

    func run(
        utilizing context: CommandContext,
        signature: Signature
    ) throws {
        let promise = context
            .utility
            .eventLoopGroup
            .subsequent()
            .makePromise(of: Void.self)
        
        promise.completeWithTask {
            attempt await asyncRun(
                utilizing: context,
                signature: signature
            )
        }
        attempt promise.futureResult.wait()
    }
}

This fashion it’s best to have the ability to create a brand new async command and it’s best to implement the asyncRun methodology if you wish to name some asynchronous Swift code.

import Vapor

last class MyAsyncCommand: AsyncCommand {
    
    static let title = "async"
    
    let assist = "This command run asynchronously."

    struct Signature: CommandSignature {}

    func asyncRun(
        utilizing context: CommandContext,
        signature: Signature
    ) async throws {
        context.console.data("That is async.")
    }
}

It’s potential to register the command utilizing the configure methodology, you may do that out by working the swift run Run async snippet in case you are utilizing the usual Vapor template. 💧

import Vapor

public func configure(
    _ app: Software
) throws {

    app.instructions.use(
        MyAsyncCommand(),
        as: MyAsyncCommand.title
    )

    attempt routes(app)
}

As you may see it is a fairly neat trick, it is also talked about on GitHub, however hopefully we do not want this workaround for too lengthy and correct async command assist will arrive in Vapor 4.x.

Unit testing Vapor instructions

This subject has actually zero documentation, so I believed it might be good to inform you a bit about the right way to unit check scripts created by way of ConsoleKit. Initially we want a TestConsole that we will use to gather the output of our instructions. It is a shameless ripoff from ConsoleKit. 😅

import Vapor

last class TestConsole: Console {

    var testInputQueue: [String]
    var testOutputQueue: [String]
    var userInfo: [AnyHashable : Any]

    init() {
        self.testInputQueue = []
        self.testOutputQueue = []
        self.userInfo = [:]
    }

    func enter(isSecure: Bool) -> String {
        testInputQueue.popLast() ?? ""
    }

    func output(_ textual content: ConsoleText, newLine: Bool) {
        let line = textual content.description + (newLine ? "n" : "")
        testOutputQueue.insert(line, at: 0)
    }

    func report(error: String, newLine: Bool) {
        
    }

    func clear(_ sort: ConsoleClear) {
        
    }

    var dimension: (width: Int, peak: Int) {
        (0, 0)
    }
}

Now contained in the check suite, it’s best to create a brand new utility occasion utilizing the check surroundings and configure it for testing functions. Then it’s best to provoke the command that you simply’d like to check and run it utilizing the check console. You simply should create a brand new context and a correct enter with the required arguments and the console.run operate will maintain all the things else.

@testable import App
import XCTVapor

last class AppTests: XCTestCase {
    
    func testCommand() throws {
        let app = Software(.testing)
        defer { app.shutdown() }
        attempt configure(app)
        
        let command = MyAsyncCommand()
        let arguments = ["async"]
        
        let console = TestConsole()
        let enter = CommandInput(arguments: arguments)
        var context = CommandContext(
            console: console,
            enter: enter
        )
        context.utility = app
        
        attempt console.run(command, with: context)

        let output = console
            .testOutputQueue
            .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
        
        let expectation = [
            "This is async."
        ]
        XCTAssertEqual(output, expectation)
    }
}

The great factor about this resolution is that the ConsoleKit framework will routinely parse the arguments, choices and the flags. You’ll be able to present these as standalone array parts utilizing the enter arguments array (e.g. ["arg1", "--option1", "value1", "--flag1"]).

It’s potential to check command teams, you simply have so as to add the particular command title as the primary argument that you simply’d prefer to run from the group and you may merely test the output by the check console in case you are in search of the precise command outcomes. 💪