From 76567c8bc56a07f56ca18fd35f676d8e8d44c68d Mon Sep 17 00:00:00 2001
From: Luke Howard <lukeh@padl.com>
Date: Mon, 2 Dec 2024 09:44:07 +1100
Subject: [PATCH] Don't use Observation on non-Darwin platforms

Workaround for swiftlang/swift#75670
---
 Sources/SwiftOCA/OCC/ControlClasses/Root.swift      |  6 ++++++
 Sources/SwiftOCA/OCC/PropertyTypes/Property.swift   |  5 ++++-
 Sources/SwiftOCA/OCP.1/Ocp1Connection+Connect.swift | 13 ++++++++++++-
 Sources/SwiftOCA/OCP.1/Ocp1Connection.swift         |  8 ++++++++
 4 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/Sources/SwiftOCA/OCC/ControlClasses/Root.swift b/Sources/SwiftOCA/OCC/ControlClasses/Root.swift
index 61d6b20..01b75d2 100644
--- a/Sources/SwiftOCA/OCC/ControlClasses/Root.swift
+++ b/Sources/SwiftOCA/OCC/ControlClasses/Root.swift
@@ -16,7 +16,9 @@
 
 import AsyncExtensions
 import Foundation
+#if canImport(Darwin)
 import Observation
+#endif
 
 open class OcaRoot: CustomStringConvertible, @unchecked Sendable,
   _OcaObjectKeyPathRepresentable, Observable
@@ -26,7 +28,9 @@ open class OcaRoot: CustomStringConvertible, @unchecked Sendable,
   public internal(set) weak var connectionDelegate: Ocp1Connection?
 
   fileprivate var subscriptionCancellable: Ocp1Connection.SubscriptionCancellable?
+  #if canImport(Darwin)
   fileprivate let _$observationRegistrar = Observation.ObservationRegistrar()
+  #endif
 
   // 1.1
   open class var classID: OcaClassID { OcaClassID("1") }
@@ -189,6 +193,7 @@ extension _OcaObjectKeyPathRepresentable where Self: OcaRoot {
     }
   }
 
+  #if canImport(Darwin)
   nonisolated func access(
     keyPath: KeyPath<Self, some Any>
   ) {
@@ -201,6 +206,7 @@ extension _OcaObjectKeyPathRepresentable where Self: OcaRoot {
   ) rethrows -> T {
     try _$observationRegistrar.withMutation(of: self, keyPath: keyPath, mutation)
   }
+  #endif
 }
 
 public extension OcaRoot {
diff --git a/Sources/SwiftOCA/OCC/PropertyTypes/Property.swift b/Sources/SwiftOCA/OCC/PropertyTypes/Property.swift
index 725e71d..ffc8800 100644
--- a/Sources/SwiftOCA/OCC/PropertyTypes/Property.swift
+++ b/Sources/SwiftOCA/OCC/PropertyTypes/Property.swift
@@ -17,7 +17,9 @@
 import AsyncAlgorithms
 import AsyncExtensions
 import Foundation
+#if canImport(Darwin)
 import Observation
+#endif
 
 public struct OcaPropertyResolutionFlags: OptionSet, Sendable {
   public typealias RawValue = UInt32
@@ -241,14 +243,15 @@ public struct OcaProperty<Value: Codable & Sendable>: Codable, Sendable,
     _enclosingInstance object: T,
     wrapped wrappedKeyPath: ReferenceWritableKeyPath<T, PropertyValue>
   ) {
+    #if canImport(Darwin)
     object.access(keyPath: wrappedKeyPath)
-
     _send = { @Sendable [subject] object, newValue in
       guard let object else { return }
       (object as! T).withMutation(keyPath: wrappedKeyPath) {
         subject.send(newValue)
       }
     }
+    #endif
   }
 
   public static subscript<T: OcaRoot>(
diff --git a/Sources/SwiftOCA/OCP.1/Ocp1Connection+Connect.swift b/Sources/SwiftOCA/OCP.1/Ocp1Connection+Connect.swift
index 2b8a5c8..972198f 100644
--- a/Sources/SwiftOCA/OCP.1/Ocp1Connection+Connect.swift
+++ b/Sources/SwiftOCA/OCP.1/Ocp1Connection+Connect.swift
@@ -20,6 +20,9 @@ import AsyncExtensions
 import Foundation
 import Logging
 import SystemPackage
+#if canImport(Darwin)
+import Observation
+#endif
 
 private extension Ocp1Error {
   var ocp1ConnectionState: Ocp1ConnectionState? {
@@ -101,6 +104,7 @@ private extension Ocp1ConnectionState {
 
 // MARK: - connection state observation
 
+#if canImport(Darwin)
 extension Ocp1Connection {
   nonisolated func access(
     keyPath: KeyPath<Ocp1Connection, some Any>
@@ -115,6 +119,7 @@ extension Ocp1Connection {
     try _$observationRegistrar.withMutation(of: self, keyPath: keyPath, mutation)
   }
 }
+#endif
 
 // MARK: - monitor task management
 
@@ -173,10 +178,14 @@ extension Ocp1Connection {
 
   /// wrapper to update the connection state, logging the old and new connection states
   private func _updateConnectionState(_ connectionState: Ocp1ConnectionState) {
+    logger.trace("_updateConnectionState: \(currentConnectionState) => \(connectionState)")
+    #if canImport(Darwin)
     withMutation(keyPath: \.currentConnectionState) {
-      logger.trace("_updateConnectionState: \(currentConnectionState) => \(connectionState)")
       _connectionState.send(connectionState)
     }
+    #else
+    _connectionState.send(connectionState)
+    #endif
   }
 
   /// update the device connection state, called from the connection (for
@@ -279,7 +288,9 @@ extension Ocp1Connection {
   }
 
   public var currentConnectionState: Ocp1ConnectionState {
+#if canImport(Darwin)
     access(keyPath: \.currentConnectionState)
+#endif
     return _connectionState.value
   }
 
diff --git a/Sources/SwiftOCA/OCP.1/Ocp1Connection.swift b/Sources/SwiftOCA/OCP.1/Ocp1Connection.swift
index 784e1ad..a2879dc 100644
--- a/Sources/SwiftOCA/OCP.1/Ocp1Connection.swift
+++ b/Sources/SwiftOCA/OCP.1/Ocp1Connection.swift
@@ -20,7 +20,9 @@ import Atomics
 @preconcurrency
 import Foundation
 import Logging
+#if canImport(Darwin)
 import Observation
+#endif
 
 package let Ocp1MaximumDatagramPduSize = 1500
 
@@ -154,6 +156,10 @@ public struct Ocp1ConnectionStatistics: Sendable {
 
 private let CommandHandleBase = OcaUint32(100)
 
+#if !canImport(Darwin)
+protocol Observable {}
+#endif
+
 @OcaConnection
 open class Ocp1Connection: Observable, CustomStringConvertible {
   public nonisolated static let MinimumPduSize = 7
@@ -203,7 +209,9 @@ open class Ocp1Connection: Observable, CustomStringConvertible {
   var subscriptions = [OcaEvent: EventSubscriptions]()
   var logger = Logger(label: "com.padl.SwiftOCA")
   var connectionID = 0
+  #if canImport(Darwin)
   let _$observationRegistrar = Observation.ObservationRegistrar()
+  #endif
 
   private var nextCommandHandle = CommandHandleBase