Auto Synthesizer for Equatable

AutoEquatable.swift

// MARK: - Compare + Mirror
private func compareSome<T>(lhs: T, rhs: T, beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer: Bool) -> Bool {
    compareAny(lhs: lhs, rhs: rhs, beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer: beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer)
}

private func compareAny(lhs: Any, rhs: Any, beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer: Bool = true) -> Bool {
    let lMirror = Mirror(reflecting: lhs)
    let rMirror = Mirror(reflecting: rhs)
    
    guard
        lMirror.displayStyle == rMirror.displayStyle,
        lMirror.children.count == rMirror.children.count
        else
    { return false }
    
    for indexInt in 0..<lMirror.children.count {
        let index = AnyCollection<(label: Optional<String>, value: Any)>.Index(indexInt)
        let lChild = lMirror.children[index]
        let rChild = rMirror.children[index]
        
        guard lChild.label == rChild.label else {
            return false
        }
        
        guard "\(lChild.value)" ==  "\(rChild.value)" else {
            let lChildType = type(of: lChild.value)
            let rChildType = type(of: rChild.value)
            if beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer && "\(lChildType)" == "\(rChildType)" {
                continue
            } else {
                return false
            }
        }
    }
    
    return true
}

// MARK: - AutoEquatable
public protocol AutoEquatable: Equatable {
    static func compare(lhs: Self, rhs: Self, beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer: Bool) -> Bool
}

public extension AutoEquatable {
    
    static func compare(lhs: Self, rhs: Self, beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer: Bool) -> Bool {
        compareSome(lhs: lhs, rhs: rhs, beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer: beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer)
    }
}


// MARK: - Equatable
public extension AutoEquatable {
    static func == (lhs: Self, rhs: Self) -> Bool {
        Self.compare(lhs: lhs, rhs: rhs, beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer: true)
    }
}

// MARK: - ErrorAutoEquatable
public typealias ErrorAutoEquatable = Swift.Error & AutoEquatable

public func == <LHS>(lhs: LHS, rhsAnyError: Swift.Error) -> Bool where LHS: ErrorAutoEquatable {
    guard let rhs = rhsAnyError as? LHS else { return false }
    return compareSome(lhs: lhs, rhs: rhs, beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer: true)
}

public func == <RHS>(lhsAnyError: Swift.Error, rhs: RHS) -> Bool where RHS: ErrorAutoEquatable {
    guard let lhs = lhsAnyError as? RHS else { return false }
    return compareSome(lhs: lhs, rhs: rhs, beSatisfiedWithSameAssociatedTypeIfTheirValuesDiffer: true)
}

// MARK: - Example

// MARK: Example Error types
enum AnError: ErrorAutoEquatable {
    case anInt(Int)
    case aString(String?)
    case anotherInt(Int)
    case anotherString(String?)
    case aBool(Bool?)
    
    case stringAndInt(aString: String, anInt: Int)
    
    case complex(aString: String, anInt: Int, aBool: Bool, aTuple: (String, Int, Bool))
}

enum AnotherError: ErrorAutoEquatable {
    case anInt(Int)
}

// MARK: - Usage
func example() {    
    @discardableResult
    func isSame(_ lhs: AnError, _ rhs: AnError) -> Bool {
        return lhs == rhs
    }
    
    // ALL `true`
    isSame(.anInt(1), .anInt(2)) // true
    isSame(.aBool(true), .aBool(false)) // true
    isSame(.aString("Hello"), .aString("World")) // true
    isSame(.aString("Hello"), .aString(nil)) // true
    
    isSame(
        .complex(aString: "A", anInt: 1, aBool: true, aTuple: ("B", 2, false)),
        .complex(aString: "X", anInt: 8, aBool: false, aTuple: ("Y", 9, true))
    ) // true
    
    (AnError.anInt(1) as Swift.Error) == AnError.anInt(1) // true
    AnError.anInt(1) == (AnError.anInt(1) as Swift.Error) // true
    
    // ALL `false`
    isSame(.anInt(1), .anotherInt(1)) // false
    isSame(.aString("Hello"), .anotherString("World")) // false
    isSame(.aString(nil), .anotherString(nil)) // false
    
    (AnError.anInt(1) as Swift.Error) == AnotherError.anInt(1) // false
    AnError.anInt(1) == (AnotherError.anInt(1) as Swift.Error) // false
    
    
}

// MARK: Advanced - 'Static' (using Functions)


protocol EmptyInitializable {
    init()
}
protocol ValueIgnored {
    static var irrelevant: Self { get }
}
typealias Ignored = EmptyInitializable & ValueIgnored
extension ValueIgnored where Self: EmptyInitializable {
    static var irrelevant: Self { .init() }
}

func == <E, A>(instance: E, make: (A) -> E) -> Bool where E: ErrorAutoEquatable, A: Ignored {
    instance == make(A.irrelevant)
}
func != <E, A>(instance: E, make: (A) -> E) -> Bool where E: ErrorAutoEquatable, A: Ignored {
    !(instance == make)
}
func == <E, A, B>(instance: E, make: (A, B) -> E) -> Bool where E: ErrorAutoEquatable, A: Ignored, B: Ignored {
    instance == make(A.irrelevant, B.irrelevant)
}

extension String: Ignored {}
extension Bool: Ignored {}

extension UInt: Ignored {}
extension UInt64: Ignored {}
extension UInt32: Ignored {}
extension UInt16: Ignored {}
extension UInt8: Ignored {}

extension Int: Ignored {}
extension Int64: Ignored {}
extension Int32: Ignored {}
extension Int16: Ignored {}
extension Int8: Ignored {}

// MARK: Advanced example
func advanced() {
    AnError.anInt(1) == AnError.self.anInt // true
    AnError.stringAndInt(aString: "Some string", anInt: 123) != AnError.self.anInt // true, not equal
    AnError.stringAndInt(aString: "Some string", anInt: 123) == AnError.stringAndInt // true
}