fix: cache appearance values from runtime setters

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 14:34 EDT:
+
+- Simulator-only rule remains active. Do not use physical iPhone/iPad devices.
+- GitHub Actions run `28391820808` on `58e5522d` recovered macOS:
+  setup, dependency install, FFI boundary check, V8 download, libffi build,
+  metadata generation, NativeScript build, CLI build, and macOS tests all
+  passed.
+- iOS simulator still failed in `ApiTests.js Appearance`, but now logged a
+  concrete Jasmine failure before timing out waiting for JUnit:
+  `Expected undefined to be { }`.
+- The failure maps to `UILabel.appearance().textColor`: assigning through the
+  safe own accessor did not populate the target-class-scoped appearance cache,
+  so the next `UILabel.appearance().textColor` read returned `undefined`.
+- Current runtime fix:
+  - UIAppearance own property accessors now install a setter for every
+    non-readonly target-class property.
+  - If generated metadata lacks an explicit setter selector, the setter uses
+    the existing runtime Objective-C property setter discovery path
+    (`runtimeWritablePropertySetter`) before caching the assigned value.
+  - Source coverage now scopes this guard to the UIAppearance accessor block.
+- 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 the setter-fallback correction and watch fresh PR CI.
+  - If CI turns green, resume the dedicated simulator-only RNS parity sweep.
+
 Update from 2026-06-29 13:47 EDT:
 
 - Simulator-only rule remains active. Do not use physical iPhone/iPad devices.

NativeScript/ffi/shared/bridge/HostObjects.mm

@@ -1967,13 +1967,22 @@ Function makeAppearanceProxyPropertySetter(
           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);
+        if (!member.setterSelectorName.empty()) {
+          NativeApiMember setterMember = member;
+          setterMember.selectorName = member.setterSelectorName;
+          setterMember.signatureOffset = member.setterSignatureOffset;
+          callObjCSelector(runtime, bridge, native, false,
+                           setterMember.selectorName, &setterMember,
+                           setterArgs, 1);
+        } else if (auto setterSelectorName =
+                       runtimeWritablePropertySetter(native, member.name)) {
+          callObjCSelector(runtime, bridge, native, false, *setterSelectorName,
+                           nullptr, setterArgs, 1);
+        } else {
+          throw JSError(runtime,
+                        "UIAppearance property setter is unavailable.");
+        }
         cacheAppearanceProxyPropertyValue(runtime, bridge, native, member.name,
                                           args[0]);
         return Value::undefined();
@@ -2014,7 +2023,7 @@ void installAppearanceProxyPropertyAccessors(
           runtime, "get",
           makeAppearanceProxyPropertyGetter(runtime, bridge, native,
                                             retainedNative, member.name));
-      if (!member.readonly && !member.setterSelectorName.empty()) {
+      if (!member.readonly) {
         descriptor.setProperty(
             runtime, "set",
             makeAppearanceProxyPropertySetter(runtime, bridge, native,

PROGRESS.md

@@ -17,6 +17,43 @@ TypeScript/UI worklets.
 
 ## Latest Update - 2026-06-29
 
+### 2026-06-29 14:34 EDT - UIAppearance setter fallback for cache
+
+- 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 `28391820808` on `58e5522d` recovered macOS:
+    setup, dependency install, FFI boundary check, V8 download, libffi build,
+    metadata generation, NativeScript build, CLI build, and macOS tests all
+    passed.
+  - iOS simulator still failed in `ApiTests.js Appearance`, but now logged a
+    concrete Jasmine failure before timing out waiting for JUnit:
+    `Expected undefined to be { }`.
+  - That maps to `UILabel.appearance().textColor`: assignment returned without
+    populating the target-class-scoped appearance cache, so the next
+    `UILabel.appearance().textColor` read was still `undefined`.
+- Changes:
+  - UIAppearance own property accessors now install a setter for every
+    non-readonly target-class property.
+  - When generated metadata does not carry an explicit setter selector, the
+    setter uses the existing runtime Objective-C property setter discovery
+    path (`runtimeWritablePropertySetter`) before caching the assigned value.
+  - Source coverage now guards this fallback and keeps the accessor cache path
+    specific to the UIAppearance block.
+- 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 the setter-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 13:47 EDT - limit UIAppearance tagging to UIKit proxies
 
 - Goal:

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

@@ -40,6 +40,17 @@ const runtimeHostObjects = fs.readFileSync(
   path.join(repoRoot, "NativeScript/ffi/shared/bridge/HostObjects.mm"),
   "utf8",
 );
+const appearanceAccessorStart = runtimeHostObjects.indexOf(
+  "Function makeAppearanceProxyPropertySetter(",
+);
+const appearanceAccessorEnd = runtimeHostObjects.indexOf(
+  "\nValue tagStaticAppearanceSelectorResult(",
+  appearanceAccessorStart,
+);
+const appearanceAccessorSource = runtimeHostObjects.slice(
+  appearanceAccessorStart,
+  appearanceAccessorEnd,
+);
 
 assert(
   runtimeHostObjects.includes("Class tagStaticAppearanceNativeResult(") &&
@@ -56,7 +67,10 @@ assert(
   runtimeHostObjects.includes("installAppearanceProxyPropertyAccessors") &&
     runtimeHostObjects.includes("makeAppearanceProxyPropertySetter") &&
     runtimeHostObjects.includes("makeAppearanceProxyPropertyGetter") &&
-    runtimeHostObjects.includes("cacheAppearanceProxyPropertyValue("),
+    runtimeHostObjects.includes("cacheAppearanceProxyPropertyValue(") &&
+    appearanceAccessorSource.includes("runtimeWritablePropertySetter(native, member.name)") &&
+    appearanceAccessorSource.includes("if (!member.readonly)") &&
+    !appearanceAccessorSource.includes("!member.readonly && !member.setterSelectorName.empty()"),
   "runtime UIAppearance proxies should install safe property accessors backed by the appearance cache",
 );
 assert(