Operating and testing async Vapor instructions

Easy methods to run async instructions in Vapor?

The async / await characteristic is comparatively new in Swift and a few framework authors have not transformed every little thing to make the most of these new key phrases. At present, that is the scenario with the Command API in Vapor 4. You’ll be able to already outline async instructions, however there is not any method to register them utilizing the Vapor framework. Luckily, there’s a comparatively simple 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 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 of 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

ultimate 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.data("That is async.")
    }
}

It’s attainable to register the command utilizing the configure methodology, you possibly can 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.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 will be good to inform you a bit about the way to unit take a look at scripts created by way of ConsoleKit. To start with we’d like a TestConsole that we will use to gather the output of our instructions. This can be a shameless ripoff from ConsoleKit. 😅

import Vapor

ultimate 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, it is best to create a brand new software occasion utilizing the take a look at atmosphere and configure it for testing functions. Then it is best to 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 required arguments and the console.run operate will handle every little thing else.

@testable import App
import XCTVapor

ultimate 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 answer is that the ConsoleKit framework will mechanically parse the arguments, choices and the flags. You’ll be able to present these as standalone array components 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 simply’d prefer to run from the group and you may merely test the output by the take a look at console in case you are on the lookout for the precise command outcomes. 💪