Add Codable Support for Swift 4.x

[csantanapr]

Codable Support with Swift 4.x

Some examples of using Codable In and Out

Codable style function signature

Create file helloCodableAsync.swift

// Domain model/entity
struct Employee: Codable {
  let id: Int?
  let name: String?
}
// codable main function
func main(input: Employee, respondWith: (Employee?, Error?) -> Void) -> Void {
    // For simplicity, just passing same Employee instance forward
    respondWith(input, nil)
}

wsk action update helloCodableAsync helloCodableAsync.swift swift:4.1

ok: updated action helloCodableAsync

wsk action invoke helloCodableAsync -r -p id 42 -p name Carlos

{
    "id": 42,
    "name": "Carlos"
}

Codable Error Handling

Create file helloCodableAsync.swift

struct Employee: Codable {
    let id: Int?
    let name: String?
}
enum VendingMachineError: Error {
    case invalidSelection
    case insufficientFunds(coinsNeeded: Int)
    case outOfStock
}
func main(input: Employee, respondWith: (Employee?, Error?) -> Void) -> Void {
    // Return real error
    do{
        throw VendingMachineError.insufficientFunds(coinsNeeded: 5)
    } catch {
        respondWith(nil, error)
    } 
}

wsk action update helloCodableError helloCodableError.swift swift:4.1

ok: updated action helloCodableError

wsk action invoke helloCodableError -b -p id 42 -p name Carlos

{
"name": "helloCodableError",
"response": {
  "result": {
    "error": "insufficientFunds(5)"
  },
"status": "application error",
"success": false
}

[csantanapr]

Depends on #22
Closes #2

[csantanapr]

TODOs

• Handle when input params is empty
• Add tests cases for Codable

[jthomas]

I've been testing out Codable support from the sample above in my library for wrapping Swift actions to produce binaries.
https://github.com/jthomas/OpenWhiskAction/blob/swift4/Sources/epilogue.swift

It's all working great but I made a few changes to improve the developer experience that we'd probably want to include. Here are the things I found....

• Support @escaping closures to allow users to use with async calls.

func _run_main<In: Codable, Out: Codable>(mainFunction: (In, @escaping (Out?, Error?) -> Void) -> Void) {
}

This just needs the annotation adding and doesn't affect existing code or people who don't use that.

• Improved error handled to give more descriptive messages, e.g.
  https://github.com/jthomas/OpenWhiskAction/blob/swift4/Sources/epilogue.swift#L84-L93

This helps the user understand when there has been problems using the Codable API versus something else.

• Sync method style APIs should probably support throws. This enables uses to use normal error handling to surface issues.

I'm away on vacation for a week but will attempt to push a PR when I return.

[csantanapr]

Thanks @jthomas for the review and starting the work to externalize the epilogue in to it's own library/package.

Support @escaping closures to allow users to use with async calls.

func _run_main<In: Codable, Out: Codable>(mainFunction: (In, @escaping (Out?, Error?) -> Void) -> Void) {
}

This just needs the annotation adding and doesn't affect existing code or people who don't use that.

Guess what I have in my TODOs?

TODOS:

• Finish with the Codable test cases
• Use @escaping instead for the callback
• Refresh again with latest 4.1 snapshot
• With now 4.2 announced 4.1 is stable, so skip/remove 4.0 support only do 4.1 for now

https://github.com/jthomas/OpenWhiskAction/blob/swift4/Sources/epilogue.swift#L84-L93
This helps the user understand when there has been problems using the Codable API versus something else.

I will add the one for more verbose errors 👍

• Improved error handled to give more descriptive messages, e.g.

Sync method style APIs should probably support throws. This enables uses to use normal error handling to surface issues.

I thought about this one, will look into this but probably a different PR since it's an improvement to dictionary sync that we have today.
#29

Super happy that someone is trying this stuff 🎉

[csantanapr]

Woot !

• Finish with the Codable test cases

[csantanapr]

Woot !

• Refresh again with latest 4.1 snapshot

[csantanapr]

Woot !

• Use @escaping instead for the callback

[csantanapr]

Woot !

• Improved error handled to give more descriptive messages, e.g.

[csantanapr]

With now 4.2 announced 4.1 is stable, so skip/remove 4.0 support only do 4.1 for now

Going to move this to a new issue #30

[csantanapr]

I think I'm ready for review and final merge of this PR

[paulcastro]

Hmmmm, can't edit each line individually. Here are some typos:

Line 209: All your source code needs to be copied ...
Line 231: Take into account that starting ...

[csantanapr]

updated the readme with typos fixes @paulcastro

[paulcastro]

What's JFailed ? Typo?

[csantanapr]

yeah Typo