Add Support for Swift 5.7

[Andrea-Scuderi]

Add support for Swift 5.7

• Add new action signatures with async/await and throws
• Backward compatibility with old action signatures

swift57Action

• Add support async to Whisk class

swiftbuild.py

• simplify the code added by the build process to:

try await _WhiskRuntime.wiskRunLoop { jsonData in
   await _WhiskRuntime.runAsyncMain(mainFunction: <action>, json: jsonData)
}

swiftbuild.py.launcher.swift

• Add _WhiskRuntime struct
• Refactor Error messages
• Add new signatures

// Examples of Actions supported by Swift 5.7

// Action with Any Input and Any Output
func main(args: Any) -> Any {
    let newArgs = args as! [String:Any]
    if let name = newArgs["name"] as? String {
        return [ "greeting" : "Hello \(name)!" ]
    } else {
        return [ "greeting" : "Hello stranger!" ]
    }
}
 
// Async Action with Any Input and Any Output
func mainAsync(args: Any) async -> Any {
    do {
        //async code sleep for 1 sec
        try await Task.sleep(nanoseconds: 1_000_000_000)
        
        let newArgs = args as! [String:Any]
        if let name = newArgs["name"] as? String {
            return [ "greeting" : "Hello \(name)!" ]
        } else {
            return [ "greeting" : "Hello stranger!" ]
        }
    } catch {
        return ["error" : error.localizedDescription]
    }
}

// Async throwing Action with Any Input and Any Output
func mainAsyncThrows(args: Any) async throws -> Any {
    //async code sleep for 1 sec
    try await Task.sleep(nanoseconds: 1_000_000_000)
    
    let newArgs = args as! [String:Any]
    if let name = newArgs["name"] as? String {
        return [ "greeting" : "Hello \(name)!" ]
    } else {
        return [ "greeting" : "Hello stranger!" ]
    }
}

struct Input: Codable {
    let name: String?
}

struct Output: Codable {
    let count: Int
}

// Action with Codable Input and completion with Codable Output and Error
func mainCompletionCodable(input: Input, completion: @escaping (Output?, Error?) -> Void) -> Void {
    if let name = input.name {
        let output = Output(count: name.count)
        completion(output, nil)
    } else {
        let output = Output(count: 0)
        completion(output, nil)
    }
}

// Action with Codable Input and completion with Codable Output and Error
func mainCompletionCodableNoInput(completion: @escaping (Output?, Error?) -> Void) -> Void {
    let output = Output(count: 0)
    completion(output, nil)
}

// Async throwing Action with Codable Output
func mainCodableAsyncThrowsNoInput() async throws -> Output? {
    try await Task.sleep(nanoseconds: 1_000_000_000)
    return Output(count: 0)
}

// Async throwing Action with a Codable Input and a Codable Output
func mainCodableAsyncThrows(input: Input) async throws -> Output? {
    try await Task.sleep(nanoseconds: 1_000_000_000)
    if let name = input.name {
        return Output(count: name.count)
    } else {
        return Output(count: 0)
    }
}

Merry Christmas and Happy New Year! 🎄

[rabbah]

Thanks @Andrea-Scuderi for this contribution.

Do you have an Apache CLA on file I was not able to locate one.

We may continue to hold merging this PR until we've cut over to the new GHA flow and away from Travis.

[Andrea-Scuderi]

Do you have an Apache CLA on file I was not able to locate one.

Yes, I've sent a CLA the 11/11/2019.

[dgrove-oss]

Hi @Andrea-Scuderi -- we've finally managed to get GitHub Action based CI working for this repository. Apologies for the very long delay. Would you have the time and interest to rebase this PR to the current master so we can get it merged?

[dgrove-oss]

If you have the time to accept the two small changes to the CHANGELOG files and update the .github/workflows/ci.yml that would be great.

[Andrea-Scuderi]

@dgrove-oss I've updated the branch with your suggestions. Could you run the CI?
Thanks

[dgrove-oss]

Thanks for the quick response! CI run approved.

[dgrove-oss]

LGTM -- Thanks for your patience!