Fallback to Perception on iOS 17 beta builds

Sources/Perception/Internal/BetaChecking.swift

@@ -0,0 +1,27 @@
+import Foundation
+
+// NB: This boolean is used to work around a crash experienced by beta users of Observation when
+//     `Observable` was still a marker protocol and we attempt to dynamically cast to
+//     `any Observable`.
+let isObservationBeta: Bool = {
+  #if os(iOS) || os(tvOS) || os(watchOS)
+    let os = ProcessInfo.processInfo.operatingSystemVersion
+    #if os(iOS) || os(tvOS)
+      if (os.majorVersion, os.minorVersion, os.patchVersion) != (17, 0, 0) {
+        return false
+      }
+    #elseif os(watchOS)
+      if (os.majorVersion, os.minorVersion, os.patchVersion) != (10, 0, 0) {
+        return false
+      }
+    #endif
+    var size = 0
+    sysctlbyname("kern.osversion", nil, &size, nil, 0)
+    var version = [CChar](repeating: 0, count: size)
+    let ret = sysctlbyname("kern.osversion", &version, &size, nil, 0)
+    // NB: Beta builds end with a lowercase character (_e.g._, '21A5277j')
+    return ret == 0 ? String(cString: version).last?.isLowercase == true : false
+  #else
+    return false
+  #endif
+}()

Sources/Perception/PerceptionRegistrar.swift

@@ -23,7 +23,7 @@ public struct PerceptionRegistrar: Sendable {
   /// ``Perception/Perceptible()`` macro to indicate observably
   /// of a type.
   public init(isPerceptionCheckingEnabled: Bool = Perception.isPerceptionCheckingEnabled) {
-    if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *) {
+    if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *), !isObservationBeta {
       #if canImport(Observation)
         self._rawValue = AnySendable(ObservationRegistrar())
       #else
@@ -90,7 +90,7 @@ extension PerceptionRegistrar {
       self.perceptionCheck(file: file, line: line)
     #endif
     #if canImport(Observation)
-      if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *) {
+      if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *), !isObservationBeta {
         func `open`<T: Observable>(_ subject: T) {
           self.registrar.access(
             subject,
@@ -112,7 +112,7 @@ extension PerceptionRegistrar {
     _ mutation: () throws -> T
   ) rethrows -> T {
     #if canImport(Observation)
-      if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *),
+      if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *), !isObservationBeta,
         let subject = subject as? any Observable
       {
         func `open`<S: Observable>(_ subject: S) throws -> T {
@@ -134,7 +134,7 @@ extension PerceptionRegistrar {
     keyPath: KeyPath<Subject, Member>
   ) {
     #if canImport(Observation)
-      if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *),
+      if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *), !isObservationBeta,
         let subject = subject as? any Observable
       {
         func `open`<S: Observable>(_ subject: S) {
@@ -155,7 +155,7 @@ extension PerceptionRegistrar {
     keyPath: KeyPath<Subject, Member>
   ) {
     #if canImport(Observation)
-      if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *),
+      if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *), !isObservationBeta,
         let subject = subject as? any Observable
       {
         func `open`<S: Observable>(_ subject: S) {

Sources/Perception/PerceptionTracking.swift

@@ -215,7 +215,7 @@ public func withPerceptionTracking<T>(
   onChange: @autoclosure () -> @Sendable () -> Void
 ) -> T {
   #if canImport(Observation)
-    if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *) {
+    if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *), !isObservationBeta {
       return withObservationTracking(apply, onChange: onChange())
     }
   #endif

Sources/Perception/WithPerceptionTracking.swift

@@ -49,7 +49,7 @@
     let content: () -> Content
 
     public var body: Content {
-      if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *) {
+      if #available(iOS 17, macOS 14, tvOS 17, watchOS 10, *), !isObservationBeta {
         return self.instrumentedBody()
       } else {
         // NB: View will not re-render when 'id' changes unless we access it in the view.