[Shared] Adds @UserInfoValue property wrapper for ALTLocalizedErrors

ALTLocalizedErrors now automatically include all properties annotated with @UserInfoValue in userInfo when bridged to NSError.

Shared/Errors/ALTLocalizedError.swift

@@ -69,13 +69,15 @@ public extension ALTLocalizedError
     }
 
     var errorUserInfo: [String : Any] {
-        let userInfo: [String: Any?] = [
+        var userInfo: [String: Any?] = [
             NSLocalizedFailureErrorKey: self.errorFailure,
             ALTLocalizedTitleErrorKey: self.errorTitle,
 //            ALTSourceFileErrorKey: self.sourceFile, // TODO: Figure out where these come from
 //            ALTSourceLineErrorKey: self.sourceLine,
         ]
-
+        
+        userInfo.merge(self.userInfoValues) { (_, new) in new }
+        
         return userInfo.compactMapValues { $0 }
     }
 
@@ -125,6 +127,21 @@ public extension ALTLocalizedError
     }
 }
 
+private extension ALTLocalizedError
+{
+    var userInfoValues: [(String, Any)] {
+        let userInfoValues = Mirror(reflecting: self).children.compactMap { (label, value) -> (String, Any)? in
+            guard let userInfoValue = value as? any UserInfoValueProtocol,
+                  let key: any StringProtocol = userInfoValue.key ?? label?.dropFirst() // Remove leading underscore
+            else { return nil }
+
+            return (String(key), userInfoValue.wrappedValue)
+        }
+        
+        return userInfoValues
+    }
+}
+
 public struct DefaultLocalizedError<Code: ALTErrorEnum>: ALTLocalizedError
 {
     public let code: Code

Shared/Errors/UserInfoValue.swift

@@ -0,0 +1,38 @@
+//
+//  UserInfoValue.swift
+//  AltStore
+//
+//  Created by Riley Testut on 5/2/23.
+//  Copyright © 2023 Riley Testut. All rights reserved.
+//
+
+import Foundation
+
+protocol UserInfoValueProtocol<Value>
+{
+    associatedtype Value
+    
+    var key: String? { get }
+    var wrappedValue: Value { get }
+}
+
+@propertyWrapper
+public struct UserInfoValue<Value>: UserInfoValueProtocol
+{
+    public let key: String?
+    public var wrappedValue: Value
+    
+    // Necessary for memberwise initializers to work as expected
+    // https://github.com/apple/swift-evolution/blob/main/proposals/0258-property-wrappers.md#memberwise-initializers
+    public init(wrappedValue: Value)
+    {
+        self.wrappedValue = wrappedValue
+        self.key = nil
+    }
+    
+    public init(wrappedValue: Value, key: String)
+    {
+        self.wrappedValue = wrappedValue
+        self.key = key
+    }
+}