fix: cache appearance values from host sets

Author: DjDeveloperr

HANDOFF.md

@@ -111,6 +111,38 @@ During this thread `agent-device` was version `0.18.0`; the npm package is
 
 ## Current Verified State
 
+Update from 2026-06-29 15:13 EDT:
+
+- Simulator-only rule remains active. Do not use physical iPhone/iPad devices.
+- GitHub Actions run `28394366898` on `14caab6a` again kept setup,
+  dependency install, FFI boundary check, V8 download, libffi build, metadata
+  generation, NativeScript build, CLI build, and macOS tests green.
+- iOS simulator still failed in `ApiTests.js Appearance` with the same
+  `Expected undefined to be { }` `UILabel.appearance().textColor` readback.
+- Root cause refinement:
+  - The previous own-accessor setter fallback did not cover the assignment
+    route used by V8 host objects.
+  - Assignment can be handled by `NativeApiObjectHostObject::set` before the
+    own accessor setter runs, and its tagged-UIAppearance branch still rejected
+    metadata properties without `setterSelectorName`.
+- Current runtime fix:
+  - The tagged-UIAppearance host-object assignment path now uses the same
+    runtime Objective-C property setter fallback as the own accessor path.
+  - It caches the assigned value after either metadata-setter or runtime-setter
+    invocation.
+  - Source coverage now guards both UIAppearance assignment routes.
+- Local verification after this correction:
+  - `node packages/react-native/test/runtime-objc-property-setter.test.js`
+    passed.
+  - 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.
+- Not done:
+  - Commit/push this host-set fallback correction and watch fresh PR CI.
+  - If CI turns green, resume the dedicated simulator-only RNS parity sweep.
+
 Update from 2026-06-29 14:34 EDT:
 
 - Simulator-only rule remains active. Do not use physical iPhone/iPad devices.

NativeScript/ffi/shared/bridge/HostObjects.mm

@@ -1815,17 +1815,25 @@ throw JSError(
         const auto& members = bridge_->membersForClass(*symbol);
         if (const NativeApiMember* propertyMember =
                 selectWritablePropertyMember(members, property, false)) {
-          if (propertyMember->readonly ||
-              propertyMember->setterSelectorName.empty()) {
+          if (propertyMember->readonly) {
             throw JSError(
                 runtime, "Attempted to assign to readonly property.");
           }
-          NativeApiMember setterMember = *propertyMember;
-          setterMember.selectorName = propertyMember->setterSelectorName;
-          setterMember.signatureOffset = propertyMember->setterSignatureOffset;
           Value args[] = {Value(runtime, value)};
-          callObjCSelector(runtime, bridge_, object_, false,
-                           setterMember.selectorName, &setterMember, args, 1);
+          if (!propertyMember->setterSelectorName.empty()) {
+            NativeApiMember setterMember = *propertyMember;
+            setterMember.selectorName = propertyMember->setterSelectorName;
+            setterMember.signatureOffset = propertyMember->setterSignatureOffset;
+            callObjCSelector(runtime, bridge_, object_, false,
+                             setterMember.selectorName, &setterMember, args, 1);
+          } else if (auto setterSelectorName =
+                         runtimeWritablePropertySetter(object_, property)) {
+            callObjCSelector(runtime, bridge_, object_, false,
+                             *setterSelectorName, nullptr, args, 1);
+          } else {
+            throw JSError(
+                runtime, "UIAppearance property setter is unavailable.");
+          }
           cacheAppearanceProxyPropertyValue(runtime, bridge_, object_,
                                             property, value);
           NATIVE_API_SET_RETURN(true);

PROGRESS.md

@@ -17,6 +17,42 @@ TypeScript/UI worklets.
 
 ## Latest Update - 2026-06-29
 
+### 2026-06-29 15:13 EDT - UIAppearance host-set fallback
+
+- Goal:
+  - Stay on PR #46's generic runtime primitive path for the RN module branch
+    and remain simulator-only. No physical devices were used.
+- CI finding:
+  - GitHub Actions run `28394366898` on `14caab6a` again kept setup,
+    dependency install, FFI boundary check, V8 download, libffi build,
+    metadata generation, NativeScript build, CLI build, and macOS tests green.
+  - iOS simulator still failed in `ApiTests.js Appearance` with the same
+    `Expected undefined to be { }` `UILabel.appearance().textColor` readback.
+  - That means the previous own-accessor setter fallback did not cover the
+    assignment route used by V8 host objects; assignment can be handled by
+    `NativeApiObjectHostObject::set` before the own accessor setter runs.
+- Changes:
+  - The tagged-UIAppearance branch in `NativeApiObjectHostObject::set` now uses
+    the same runtime Objective-C property setter fallback when target-class
+    metadata lacks `setterSelectorName`.
+  - The branch now caches the assigned value after either metadata-setter or
+    runtime-setter invocation, so subsequent `UILabel.appearance().textColor`
+    reads should resolve through the target-class-scoped appearance cache.
+  - Source coverage now guards both the own-accessor setter and the host-object
+    assignment path.
+- Verification:
+  - `node packages/react-native/test/runtime-objc-property-setter.test.js`
+    passed.
+  - 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/linked the edited V8 bridge.
+- Still next:
+  - Commit/push this host-set fallback 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 14:34 EDT - UIAppearance setter fallback for cache
 
 - Goal:

packages/react-native/test/runtime-objc-property-setter.test.js

@@ -51,6 +51,17 @@ const appearanceAccessorSource = runtimeHostObjects.slice(
   appearanceAccessorStart,
   appearanceAccessorEnd,
 );
+const appearanceHostSetStart = runtimeHostObjects.indexOf(
+  "if (Class appearanceClass =",
+);
+const appearanceHostSetEnd = runtimeHostObjects.indexOf(
+  "\n    if (auto setterSelectorName =",
+  appearanceHostSetStart,
+);
+const appearanceHostSetSource = runtimeHostObjects.slice(
+  appearanceHostSetStart,
+  appearanceHostSetEnd,
+);
 
 assert(
   runtimeHostObjects.includes("Class tagStaticAppearanceNativeResult(") &&
@@ -73,6 +84,11 @@ assert(
     !appearanceAccessorSource.includes("!member.readonly && !member.setterSelectorName.empty()"),
   "runtime UIAppearance proxies should install safe property accessors backed by the appearance cache",
 );
+assert(
+  appearanceHostSetSource.includes("runtimeWritablePropertySetter(object_, property)") &&
+    !appearanceHostSetSource.includes("propertyMember->readonly ||\n              propertyMember->setterSelectorName.empty()"),
+  "runtime UIAppearance host-object assignment should use the same runtime setter fallback before caching",
+);
 assert(
   !runtimeHostObjects.includes("SetNativeApiObjectPrototype(runtime, resultObject"),
   "runtime UIAppearance proxies should not replace their JS prototype with the target class prototype",