fix: avoid UIAppearance proxy getter hangs

DjDeveloperr · DjDeveloperr · commit ac94954e2603 · 2026-06-29T13:23:38.000-04:00
diff --git a/HANDOFF.md b/HANDOFF.md
@@ -111,6 +111,45 @@ During this thread `agent-device` was version `0.18.0`; the npm package is
 
 ## Current Verified State
 
+Update from 2026-06-29 13:21 EDT:
+
+- Simulator-only rule remains active. Do not use physical iPhone/iPad devices.
+- GitHub Actions run `28387410928` on `c7454bc4` kept setup, dependency
+  install, FFI boundary, V8 download, libffi build, metadata generation,
+  NativeScript build, CLI build, and macOS tests green, but iOS timed out
+  without a Jasmine summary or `junit-result.xml`.
+- The timeout happened after `Application Start!` and five skipped-spec `S`
+  markers. The previous failing run reached the same point and then reported
+  `ApiTests.js Appearance`, so the target-prototype experiment likely fixed
+  the old `undefined` readback only by letting the test fall through to a
+  forwarded UIKit appearance getter hang.
+- Current runtime fix:
+  - Static `appearance*` results still tag the native proxy with the
+    customizable target class.
+  - Returned `UIAppearance` proxies now get own JS accessors for target-class
+    metadata properties instead of having their prototype replaced with the
+    target class prototype.
+  - Setters forward to UIKit and populate the target-class-scoped appearance
+    cache; getters read that cache only, avoiding speculative native getter
+    calls on UIKit's forwarded proxy.
+  - Source coverage now requires the safe accessor install and blocks
+    `SetNativeApiObjectPrototype(runtime, resultObject, ...)` for appearance
+    proxy results.
+- Local verification after this correction:
+  - Runtime RN JS tests passed:
+    `for f in packages/react-native/test/*.test.js; do node "$f" || exit 1; done`.
+  - `npm run check:ffi-boundaries` passed.
+  - `git diff --check` passed.
+  - `npm run build:macos-cli` passed.
+  - Focused simulator attempt on
+    `BF759806-2EBB-49ED-AD8E-413A7790ADE0`:
+    `IOS_DESTINATION=BF759806-2EBB-49ED-AD8E-413A7790ADE0 IOS_TESTS=ApiTests IOS_SPECS=Appearance IOS_TEST_VERBOSE_SPECS=1 IOS_LOG_JUNIT=1 IOS_TEST_TIMEOUT_MS=180000 IOS_TEST_INACTIVITY_TIMEOUT_MS=60000 npm run test:ios`
+    was blocked before app launch by the known local metadata-generator
+    `libclang.dylib` x86_64/arm64 mismatch.
+- Not done:
+  - Commit/push the safe UIAppearance accessor correction and watch fresh PR CI.
+  - If CI turns green, resume the dedicated simulator-only RNS parity sweep.
+
 Update from 2026-06-29 12:30 EDT:
 
 - Simulator-only rule remains active. Do not use physical iPhone/iPad devices.
diff --git a/NativeScript/ffi/shared/bridge/HostObjects.mm b/NativeScript/ffi/shared/bridge/HostObjects.mm
@@ -1919,32 +1919,111 @@ Class tagStaticAppearanceNativeResult(
   return customizableClass;
 }
 
-void installAppearanceProxyTargetPrototype(
+std::shared_ptr<void> retainAppearanceProxyForAccessor(id native) {
+  id retained = [native retain];
+  return std::shared_ptr<void>(static_cast<void*>(retained), [](void* value) {
+    [(id)value release];
+  });
+}
+
+bool shouldInstallAppearanceProxyAccessor(const NativeApiMember& member) {
+  if (!member.property || member.name.empty()) {
+    return false;
+  }
+  bool memberIsStatic = (member.flags & metagen::mdMemberStatic) != 0;
+  if (memberIsStatic) {
+    return false;
+  }
+  return member.name != "superclass" && member.name != "class" &&
+         member.name != "constructor" && member.name != "debugDescription" &&
+         member.name != "className" && member.name != "description";
+}
+
+Function makeAppearanceProxyPropertyGetter(
+    Runtime& runtime, std::shared_ptr<NativeApiBridge> bridge, id native,
+    std::shared_ptr<void> retainedNative, std::string property) {
+  return Function::createFromHostFunction(
+      runtime, PropNameID::forAscii(runtime, property.c_str()), 0,
+      [bridge = std::move(bridge), native, retainedNative = std::move(retainedNative),
+       property = std::move(property)](Runtime& runtime, const Value&,
+                                       const Value*, size_t) -> Value {
+        return cachedAppearanceProxyPropertyValue(runtime, bridge, native,
+                                                  property);
+      });
+}
+
+Function makeAppearanceProxyPropertySetter(
+    Runtime& runtime, std::shared_ptr<NativeApiBridge> bridge, id native,
+    std::shared_ptr<void> retainedNative, NativeApiMember member) {
+  std::string functionName = member.setterSelectorName.empty()
+                                 ? member.name
+                                 : member.setterSelectorName;
+  return Function::createFromHostFunction(
+      runtime, PropNameID::forAscii(runtime, functionName.c_str()), 1,
+      [bridge = std::move(bridge), native, retainedNative = std::move(retainedNative),
+       member = std::move(member)](Runtime& runtime, const Value&, const Value* args,
+                                   size_t count) -> Value {
+        if (count < 1) {
+          throw JSError(runtime,
+                        "UIAppearance property setter expects a value.");
+        }
+        NativeApiMember setterMember = member;
+        setterMember.selectorName = member.setterSelectorName;
+        setterMember.signatureOffset = member.setterSignatureOffset;
+        Value setterArgs[] = {Value(runtime, args[0])};
+        callObjCSelector(runtime, bridge, native, false,
+                         setterMember.selectorName, &setterMember, setterArgs,
+                         1);
+        cacheAppearanceProxyPropertyValue(runtime, bridge, native, member.name,
+                                          args[0]);
+        return Value::undefined();
+      });
+}
+
+void installAppearanceProxyPropertyAccessors(
     Runtime& runtime, const std::shared_ptr<NativeApiBridge>& bridge,
-    Class customizableClass, Object& resultObject) {
+    Class customizableClass, id native, Object& resultObject) {
   if (bridge == nullptr || customizableClass == Nil) {
     return;
   }
+  const NativeApiSymbol* symbol =
+      bridge->findClassForRuntimeClass(customizableClass);
+  if (symbol == nullptr) {
+    return;
+  }
 
-  Value prototypeValue =
-      bridge->findClassPrototype(runtime, customizableClass);
-  if (!prototypeValue.isObject()) {
-    Value classWrapperValue =
-        bridge->findClassValue(runtime, customizableClass);
-    if (!classWrapperValue.isObject()) {
-      classWrapperValue = makeNativeClassValue(
-          runtime, bridge,
-          nativeApiSymbolForRuntimeClass(bridge, customizableClass));
-    }
-    if (classWrapperValue.isObject()) {
-      prototypeValue =
-          classWrapperValue.asObject(runtime).getProperty(runtime, "prototype");
+  Object objectConstructor =
+      runtime.global().getPropertyAsObject(runtime, "Object");
+  Function defineProperty =
+      objectConstructor.getPropertyAsFunction(runtime, "defineProperty");
+  std::unordered_set<std::string> installed;
+  std::shared_ptr<void> retainedNative =
+      retainAppearanceProxyForAccessor(native);
+  const auto& members = bridge->membersForClass(*symbol);
+  for (const auto& member : members) {
+    if (!shouldInstallAppearanceProxyAccessor(member) ||
+        !installed.insert(member.name).second) {
+      continue;
     }
-  }
 
-  if (prototypeValue.isObject()) {
-    Object prototype = prototypeValue.asObject(runtime);
-    SetNativeApiObjectPrototype(runtime, resultObject, prototype);
+    try {
+      Object descriptor(runtime);
+      descriptor.setProperty(runtime, "configurable", true);
+      descriptor.setProperty(runtime, "enumerable", false);
+      descriptor.setProperty(
+          runtime, "get",
+          makeAppearanceProxyPropertyGetter(runtime, bridge, native,
+                                            retainedNative, member.name));
+      if (!member.readonly && !member.setterSelectorName.empty()) {
+        descriptor.setProperty(
+            runtime, "set",
+            makeAppearanceProxyPropertySetter(runtime, bridge, native,
+                                              retainedNative, member));
+      }
+      defineProperty.call(runtime, resultObject, makeString(runtime, member.name),
+                          descriptor);
+    } catch (const std::exception&) {
+    }
   }
 }
 
@@ -1963,8 +2042,10 @@ Value tagStaticAppearanceSelectorResult(
   Class customizableClass = tagStaticAppearanceNativeResult(
       runtime, bridge, static_cast<Class>(receiver),
       resultObject.getHostObject<NativeApiObjectHostObject>(runtime)->object());
-  installAppearanceProxyTargetPrototype(runtime, bridge, customizableClass,
-                                        resultObject);
+  installAppearanceProxyPropertyAccessors(
+      runtime, bridge, customizableClass,
+      resultObject.getHostObject<NativeApiObjectHostObject>(runtime)->object(),
+      resultObject);
   return result;
 }
 
@@ -2220,9 +2301,8 @@ throw JSError(runtime,
                 Class customizableClass =
                     tagStaticAppearanceNativeResult(runtime, bridge, cls,
                                                     native);
-                installAppearanceProxyTargetPrototype(runtime, bridge,
-                                                      customizableClass,
-                                                      resultObject);
+                installAppearanceProxyPropertyAccessors(
+                    runtime, bridge, customizableClass, native, resultObject);
               }
             }
             return result;
diff --git a/PROGRESS.md b/PROGRESS.md
@@ -17,6 +17,47 @@ TypeScript/UI worklets.
 
 ## Latest Update - 2026-06-29
 
+### 2026-06-29 13:21 EDT - safe UIAppearance proxy accessors
+
+- Goal:
+  - Keep PR #46 on generic runtime primitives and stay simulator-only; no
+    physical devices were used.
+- CI finding:
+  - GitHub Actions run `28387410928` on `c7454bc4` kept setup, dependency
+    install, FFI boundary check, V8 download, libffi build, metadata
+    generation, NativeScript build, CLI build, and macOS tests green, but iOS
+    timed out before a Jasmine summary or `junit-result.xml`.
+  - The iOS log reached `Application Start!`, printed five skipped-spec `S`
+    markers, then went silent until the 10 minute watchdog. The previous run
+    reached the same point and failed in `ApiTests.js Appearance`, so the
+    target-prototype approach likely moved the test into a forwarded UIKit
+    appearance getter hang.
+- Changes:
+  - Replaced target-class prototype mutation with own property accessors on
+    returned `UIAppearance` proxies.
+  - The accessors are installed from the customizable target class metadata:
+    setters forward to UIKit and populate the target-class-scoped appearance
+    cache; getters read only that cache and avoid speculative native getter
+    calls on UIKit's forwarded proxy.
+  - Source coverage now guards both the safe accessor install and the absence
+    of `SetNativeApiObjectPrototype(runtime, resultObject, ...)` on appearance
+    proxies.
+- Verification:
+  - Runtime RN JS tests passed:
+    `for f in packages/react-native/test/*.test.js; do node "$f" || exit 1; done`.
+  - `npm run check:ffi-boundaries` passed.
+  - `git diff --check` passed.
+  - `npm run build:macos-cli` passed and compiled the edited V8 bridge.
+  - Focused simulator attempt on the dedicated sim:
+    `IOS_DESTINATION=BF759806-2EBB-49ED-AD8E-413A7790ADE0 IOS_TESTS=ApiTests IOS_SPECS=Appearance IOS_TEST_VERBOSE_SPECS=1 IOS_LOG_JUNIT=1 IOS_TEST_TIMEOUT_MS=180000 IOS_TEST_INACTIVITY_TIMEOUT_MS=60000 npm run test:ios`
+    did not launch the app because local `build_metadata_generator.sh` still
+    fails linking the x86_64 metadata generator against an arm64-only
+    `libclang.dylib`.
+- Still next:
+  - Commit/push the safe-accessor correction and watch fresh PR CI for the
+    authoritative iOS simulator result.
+  - If CI turns green, resume the dedicated simulator-only RNS parity sweep.
+
 ### 2026-06-29 12:30 EDT - installed UIAppearance target prototypes
 
 - Goal:
diff --git a/packages/react-native/test/runtime-objc-property-setter.test.js b/packages/react-native/test/runtime-objc-property-setter.test.js
@@ -47,11 +47,15 @@ assert(
   "runtime UIAppearance result tagging should return the customizable target class",
 );
 assert(
-  runtimeHostObjects.includes("installAppearanceProxyTargetPrototype") &&
-    runtimeHostObjects.includes(
-      "SetNativeApiObjectPrototype(runtime, resultObject, prototype);",
-    ),
-  "runtime UIAppearance proxies should install the target class prototype",
+  runtimeHostObjects.includes("installAppearanceProxyPropertyAccessors") &&
+    runtimeHostObjects.includes("makeAppearanceProxyPropertySetter") &&
+    runtimeHostObjects.includes("makeAppearanceProxyPropertyGetter") &&
+    runtimeHostObjects.includes("cacheAppearanceProxyPropertyValue("),
+  "runtime UIAppearance proxies should install safe property accessors backed by the appearance cache",
+);
+assert(
+  !runtimeHostObjects.includes("SetNativeApiObjectPrototype(runtime, resultObject"),
+  "runtime UIAppearance proxies should not replace their JS prototype with the target class prototype",
 );
 
 console.log("runtime Objective-C property setter tests passed");
