Working and testing async Vapor instructions

Methods 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 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 isn’t any solution 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 will 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 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
            .utility
            .eventLoopGroup
            .subsequent()
            .makePromise(of: Void.self)
        
        promise.completeWithTask {
            attempt await asyncRun(
                utilizing: context,
                signature: signature
            )
        }
        attempt promise.futureResult.wait()
    }
}

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

import Vapor

remaining 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
    )

    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 help will arrive in Vapor 4.x.

Unit testing Vapor instructions

This subject has actually zero documentation, so I assumed it will be good to inform you a bit about easy methods to 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

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

Now contained in the take a look at suite, it is best to create a brand new utility 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 mandatory arguments and the console.run operate will deal with all the things else.

@testable import App
import XCTVapor

remaining class AppTests: XCTestCase {
    
    func testCommand() throws {
        let app = Utility(.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 good 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 doable to check command teams, you simply have so as to add the particular command identify as the primary argument that you simply’d prefer to run from the group and you’ll merely verify the output by way of the take a look at console in case you are in search of the precise command outcomes. 💪