Working and testing async Vapor instructions

Find out how to run async instructions in Vapor?

The async / await characteristic is comparatively new in Swift and a few framework authors have not transformed every thing to benefit from these new key phrases. Presently, 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 no option to register them utilizing the Vapor framework. Luckily, there’s a comparatively simple workaround that you need to 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 lengthen 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
            .software
            .eventLoopGroup
            .subsequent()
            .makePromise(of: Void.self)
        
        promise.completeWithTask {
            strive await asyncRun(
                utilizing: context,
                signature: signature
            )
        }
        strive promise.futureResult.wait()
    }
}

This fashion it is best to be capable to create a brand new async command and it is best to implement the asyncRun methodology if you wish to name some asynchronous Swift code.

import Vapor

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

    struct Signature: CommandSignature {}

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

It’s attainable to register the command utilizing the configure methodology, you possibly can do this out by operating the swift run Run async snippet if you’re utilizing the usual Vapor template. 💧

import Vapor

public func configure(
    _ app: Software
) throws {

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

    strive routes(app)
}

As you possibly can 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 matter has actually zero documentation, so I assumed it might be good to inform you a bit about the right way to unit check scripts created by way of ConsoleKit. To begin with we’d like a TestConsole that we will use to gather the output of our instructions. It is a shameless ripoff from ConsoleKit. 😅

import Vapor

closing 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 is best to create a brand new software occasion utilizing the check surroundings and configure it for testing functions. Then it is best to provoke the command that you just’d like to check and run it utilizing the check console. You simply need to create a brand new context and a correct enter with the required arguments and the console.run operate will deal with every thing else.

@testable import App
import XCTVapor

closing class AppTests: XCTestCase {
    
    func testCommand() throws {
        let app = Software(.testing)
        defer { app.shutdown() }
        strive configure(app)
        
        let command = MyAsyncCommand()
        let arguments = ["async"]
        
        let console = TestConsole()
        let enter = CommandInput(arguments: arguments)
        var context = CommandContext(
            console: console,
            enter: enter
        )
        context.software = app
        
        strive 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 mechanically 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 attainable to check command teams, you simply have so as to add the precise command identify as the primary argument that you just’d wish to run from the group and you may merely test the output by means of the check console if you’re searching for the precise command outcomes. 💪