add key path func

Author: dankinsoid

Sources/VDFlow/EmptyStep.swift

@@ -20,12 +20,17 @@ public struct EmptyStepsCollection: StepsCollection {
 		set {}
 	}
 
+	public let none = EmptyStep()
 	public init() {}
 
 	public static func step<T>(for keyPath: WritableKeyPath<Self, StepID<T>>) -> AllSteps? {
 		AllSteps.none
 	}
 
+	public static func keyPath(for step: AllSteps) -> PartialKeyPath<EmptyStepsCollection> {
+		\.none
+	}
+	
 	public enum AllSteps: Codable, Hashable, Sendable, CaseIterable {
 
 		case none
@@ -36,11 +41,11 @@ public struct EmptyStepsCollection: StepsCollection {
 
 @available(iOS 17.0, macOS 14.0, tvOS 17.0, watchOS 10.0, *)
 extension Never: StepsCollection {
-
 	public var _lastMutateID: MutateID? { nil }
 	public var selected: Never {
 		get { fatalError() }
 		set {}
 	}
 	public static func step<T>(for keyPath: WritableKeyPath<Self, StepID<T>>) -> AllSteps? { nil }
+	public static func keyPath(for step: Never) -> PartialKeyPath<Never> { }
 }

Sources/VDFlow/StepsCollection.swift

@@ -35,6 +35,9 @@ public protocol StepsCollection {
 
 	/// Retrieves the step ID for a specific step key path.
 	static func step<T>(for keyPath: WritableKeyPath<Self, StepID<T>>) -> AllSteps?
+
+	/// Retrieves the key path for a specific step in the collection.
+	static func keyPath(for step: AllSteps) -> PartialKeyPath<Self>
 }
 
 extension StepsCollection {

Sources/VDFlowMacros/StepsMacro.swift

@@ -414,6 +414,16 @@ public struct StepsMacro: MemberAttributeMacro, ExtensionMacro, MemberMacro, Acc
 			   }
 			   """
 		result.append(stepFunc)
+
+		let keyPathFunc: DeclSyntax =
+			   """
+			   public static func keyPath(for step: AllSteps) -> PartialKeyPath<Self> {
+			       switch step {
+			       \(raw: cases.map { "case .\($0): return \\.\($0)" }.joined(separator: "\n"))
+			       }
+			   }
+			   """
+		result.append(keyPathFunc)
 		return result
 	}
 }