Adds case(of:) Validation

[mohpor]

Added Enum validation for RawRepresentable enums. Checks to see if a value can be represented as a specific enum, and if enum is CaseIterable, reports the possible values too.

e.g.:

final class TestModel: Content, Validatable {
  enum CustomEnum: String, Content, CaseIterable {
    case test, ok
  }

  let type: CustomEnum

  static func validations(_ validations: inout Validations) {
    validations.add("type", as: String.self, is: .case(of: CustomEnum.self))
  }
}

[mohpor]

@tanner0101 I can't find any circleci config files. What's happening?!

[Joannis]

@mohpor CircleCI is triggering on Vapor 4 because Vapor 3 still uses CircleCI. It's an issue between the two testing setups.

[tanner0101]

+1 to this change, thank you.

[tanner0101]

The name of the enum seems like an implementation detail to me. This failure description should be similar to the .in validator and say something like "value is not foo, bar, or baz"

[mohpor]

You're right. It's better that way. Applicable only to CaseIterables. But still.
We are going to need a better error message for non-CaseIterables.

[tanner0101]

@mohpor if you rebase your branch off latest master the circle ci build error will be fixed 👍

[mohpor]

@mohpor if you rebase your branch off latest master the circle ci build error will be fixed 👍

Done.

[mohpor]

Sorry about the mess. Should be squashed.

[tanner0101]

No problem, GitHub will squash them for us.

[tanner0101]

Thanks for the latest changes! This looks great. Just minor nits left.

[tanner0101]

Most annoying nit of all time: can we have an oxford comma here? >_<

You should be able to copy makeDescription from the .in validator (In.swift) which supports both successDescription and failureDescription and includes the comma:

    func makeDescription(not: Bool) -> String {
        let description: String
        switch self.items.count {
        case 1:
            description = self.items[0].description
        case 2:
            description = "\(self.items[0].description) or \(self.items[1].description)"
        default:
            let first = self.items[0..<(self.items.count - 1)]
                .map { $0.description }.joined(separator: ", ")
            let last = self.items[self.items.count - 1].description
            description = "\(first), or \(last)"
        }
        return "is\(not ? " not" : " ") \(description)"
    }

[mohpor]

And I was thinking how inefficient is in's description generation! >_<

[mohpor]

As a matter of fact, the in's description message has an invalid 2-space distance for successful cases.

[tanner0101]

Thanks!

[tanner0101]

These changes are now available in 4.0.0-beta.3.22