Operating and testing async Vapor instructions

The best way 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 make the most of these new key phrases. At the moment, that is the scenario with the Command API in Vapor 4. You’ll be able to already outline async instructions, however there isn’t any option to register them utilizing the Vapor framework. Fortuitously, there’s a comparatively easy workaround that you need to use if you wish to execute instructions utilizing an asynchronous context. 🔀

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

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 manner you must be capable to create a brand new async command and you must implement the asyncRun technique if you wish to name some asynchronous Swift code.

import Vapor

last 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 doable to register the command utilizing the configure technique, you may do this out by operating the swift run Run async snippet in case you are utilizing the usual Vapor template. 💧

import Vapor

public func configure(
    _ app: Utility
) throws {

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

    strive 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 help will arrive in Vapor 4.x.

Unit testing Vapor instructions

This subject has actually zero documentation, so I believed it could be good to inform you a bit about how one can unit take a look at scripts created through ConsoleKit. To start with we’d like a TestConsole that we are able to 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(_ kind: ConsoleClear) {
        
    }

    var measurement: (width: Int, top: Int) {
        (0, 0)
    }
}

Now contained in the take a look at suite, you must create a brand new software occasion utilizing the take a look at surroundings and configure it for testing functions. Then you must provoke the command that you simply’d like to check and run it utilizing the take a look at console. You simply should create a brand new context and a correct enter with the mandatory arguments and the console.run perform will maintain every thing else.

@testable import App
import XCTVapor

last class AppTests: XCTestCase {
    
    func testCommand() throws {
        let app = Utility(.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 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 doable to check command teams, you simply have so as to add the particular command identify as the primary argument that you simply’d wish to run from the group and you’ll merely test the output via the take a look at console in case you are on the lookout for the precise command outcomes. 💪