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Operating and testing async Vapor instructions

Learn how to run async instructions in Vapor?

The async / await function is comparatively new in Swift and a few framework authors have not transformed every part to make the most of 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 approach to register them utilizing the Vapor framework. Thankfully, there’s a comparatively simple 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 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
            .makePromise(of: Void.self)
        promise.completeWithTask {
            strive await asyncRun(
                utilizing: context,
                signature: signature
        strive promise.futureResult.wait()

This manner 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

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 {"That is async.")

It’s attainable to register the command utilizing the configure methodology, you’ll be able to 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: Utility
) throws {

        as: MyAsyncCommand.title

    strive routes(app)

As you’ll be able to 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 will be good to inform you a bit about find out how to unit check scripts created by way of ConsoleKit. To begin with we want a TestConsole that we will use to gather the output of our instructions. This can be 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 check suite, it is best to create a brand new utility occasion utilizing the check setting 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 check console. You simply should create a brand new context and a correct enter with the mandatory arguments and the perform will maintain every part 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.utility = app
        strive, with: context)

        let output = console
            .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 robotically 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 title as the primary argument that you simply’d wish to run from the group and you may merely test the output by way of the check console in case you are in search of the precise command outcomes. 💪



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