From 67e6d27485d6d1503ee66bf7f00f9945a551a44b Mon Sep 17 00:00:00 2001
From: Bobby Sudekum <rsudekum@gmail.com>
Date: Sun, 15 Feb 2026 11:18:48 +0100
Subject: [PATCH] Fix .onPreview/.onTest not working in Xcode previews

Two issues prevented context factories from resolving in previews:

1. Registration and resolution of preview/test contexts were gated
   behind #if DEBUG. Since isPreview and isTest are runtime checks
   (environment variables), they don't need compile-time guards.
   Removed #if DEBUG for preview/test; kept it for debug context.

2. Xcode previews dynamically recompile and inject code, causing
   nominal types (TypedFactory<P,T>) to have different type identity
   across module boundaries. The as? TypedFactory<P,T> cast silently
   fails, so context factories are ignored and the default factory
   runs instead (often fatalError).

   Fix: Added untypedFactory property to AnyFactory that exposes the
   closure as Any. When the nominal struct cast fails, resolution
   falls back to casting the closure using structural function types
   (@Sendable (P) -> T), which are identity-independent in Swift.
---
 Sources/FactoryKit/FactoryKit/Modifiers.swift   |  2 --
 .../FactoryKit/FactoryKit/Registrations.swift   | 17 ++++++++++++++---
 Sources/FactoryKit/FactoryKit/Resolver.swift    |  2 ++
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/Sources/FactoryKit/FactoryKit/Modifiers.swift b/Sources/FactoryKit/FactoryKit/Modifiers.swift
index ac4ec3a3..8097ee6d 100644
--- a/Sources/FactoryKit/FactoryKit/Modifiers.swift
+++ b/Sources/FactoryKit/FactoryKit/Modifiers.swift
@@ -175,9 +175,7 @@ extension FactoryModifying {
             case .arg, .args, .device, .simulator:
                 registration.context(context, key: registration.key, factory: factory)
             default:
-                #if DEBUG
                 registration.context(context, key: registration.key, factory: factory)
-                #endif
                 break
             }
         }
diff --git a/Sources/FactoryKit/FactoryKit/Registrations.swift b/Sources/FactoryKit/FactoryKit/Registrations.swift
index 06f5027b..33b16f15 100644
--- a/Sources/FactoryKit/FactoryKit/Registrations.swift
+++ b/Sources/FactoryKit/FactoryKit/Registrations.swift
@@ -86,11 +86,21 @@ public struct FactoryRegistration<P,T>: Sendable {
             traceNewType = "O" // .onTest, .onDebug, etc.
             #endif
             current = found.factory
+        } else if let found = options?.factoryForCurrentContext()?.untypedFactory as? @Sendable (P) -> T {
+            #if DEBUG
+            traceNewType = "O" // .onTest, .onDebug, etc. (cross-module)
+            #endif
+            current = found
         } else if let found = manager.registrations[key] as? TypedFactory<P,T> {
             #if DEBUG
             traceNewType = "R" // .register {}
             #endif
             current = found.factory
+        } else if let found = manager.registrations[key]?.untypedFactory as? @Sendable (P) -> T {
+            #if DEBUG
+            traceNewType = "R" // .register {} (cross-module)
+            #endif
+            current = found
         } else {
             #if DEBUG
             traceNewType = "F" // Factory { ... }
@@ -341,14 +351,12 @@ extension FactoryOptions {
             }
         }
         if let contexts = contexts, !contexts.isEmpty {
-            #if DEBUG
             if FactoryContext.current.isPreview, let found = contexts["preview"] {
                 return found
             }
             if FactoryContext.current.isTest, let found = contexts["test"] {
                 return found
             }
-            #endif
             if FactoryContext.current.isSimulator, let found = contexts["simulator"] {
                 return found
             }
@@ -378,8 +386,11 @@ internal struct FactoryDebugInformation {
 #endif
 
 // Internal Factory type
-internal protocol AnyFactory {}
+internal protocol AnyFactory {
+    var untypedFactory: Any { get }
+}
 
 internal struct TypedFactory<P,T>: AnyFactory {
     let factory: @Sendable (P) -> T
+    var untypedFactory: Any { factory }
 }
diff --git a/Sources/FactoryKit/FactoryKit/Resolver.swift b/Sources/FactoryKit/FactoryKit/Resolver.swift
index 7fda0774..c2fb07d4 100644
--- a/Sources/FactoryKit/FactoryKit/Resolver.swift
+++ b/Sources/FactoryKit/FactoryKit/Resolver.swift
@@ -69,6 +69,8 @@ extension Resolving {
             let key = FactoryKey(type: T.self, key: globalResolverKey)
             if let factory = manager.registrations[key] as? TypedFactory<Void,T> {
                 return Factory(FactoryRegistration<Void,T>(key: globalResolverKey, container: self, factory: factory.factory))
+            } else if let factory = manager.registrations[key]?.untypedFactory as? @Sendable (Void) -> T {
+                return Factory(FactoryRegistration<Void,T>(key: globalResolverKey, container: self, factory: factory))
             }
             // otherwise return nil
             return nil