Rubén Norte

This commit **improves code clarity** within the **`NativeMutationObserver`** module by replacing a `FIXME` comment in `NativeMutationObserver.cpp`. The previous comment questioned the safety of calling into JavaScript from the native side. The new explanation clarifies that such calls are safe because mutation checks occur synchronously during React commits, ensuring the execution is already within a JavaScript task. This **documentation enhancement** helps maintainers understand the **JavaScript interoperability** safety guarantees without altering any runtime behavior or functionality.

This commit introduces a **new capability** by adding **performance tracing instrumentation** to the **React Native renderer**, providing enhanced visibility into rendering operations. Specifically, it instruments the **Android mounting pipeline** by wrapping `MountItemDispatcher` operations and the **shared C++ renderer's commit and layout processes** within `ShadowTree::tryCommit`. This work enables developers to observe detailed renderer activity on a new "Renderer" track in **React Native Developer Tools**, facilitating the identification and optimization of rendering performance bottlenecks.

This commit **adds a new Fantom test** to **diagnose a critical bug** within the **Fabric** implementation of **event dispatching**. The test specifically highlights an issue where `currentProps` are incorrectly updated during the render phase via `cloneInstance`, leading to stale event listeners when renders are interrupted. This diagnostic test demonstrates a divergence in behavior compared to React DOM, where event handlers correctly reflect the latest props. Its purpose is to provide a reproducible scenario for this **event dispatching bug** in React Native, affecting how components handle events with potentially outdated props.

This commit introduces **new performance tracking instrumentation** within the **React Native renderer** to enhance visibility into rendering operations in **React Native DevTools performance traces**. Specifically, it instruments the **Android Fabric mounting pipeline** by wrapping `MountItemDispatcher` operations (view commands, premount, mount) with `PerformanceTracer.trace` calls, which will appear on a new "Renderer" track. Concurrently, the **C++ shared renderer's `ShadowTree::tryCommit` method** is now instrumented to track commit and layout operations, including metadata about the commit source. This **enhancement** provides developers with deeper insights into the rendering lifecycle, aiding in performance analysis and optimization.

This commit introduces a **privacy manifest** for the **`React-timing` module** within React Native's iOS implementation. It explicitly declares the use of the `mach_absolute_time()` API, categorized as `NSPrivacyAccessedAPICategorySystemBootTime` with reason code `35F9.1`, to measure elapsed time between events. This crucial **maintenance update** addresses Apple's new privacy manifest requirements, preventing potential App Store rejections for applications that rely on this timing functionality. The `PrivacyInfo.xcprivacy` file is added and integrated into the `React-timing.podspec` to ensure compliance and smooth application submission.

This commit performs a **refactoring** and **maintenance** cleanup within the **React Native feature flag system** on Android. It **removes redundant overrides** in `ReactNativeNewArchitectureFeatureFlagsDefaults.kt` and `ReactNativeFeatureFlagsOverrides_RNOSS_Stable_Android.kt` where the overridden values were identical to their parent class defaults. Specifically, it simplifies methods like `useFabricInterop()` and those related to the new architecture (e.g., `enableBridgelessArchitecture`, `useTurboModules`) by removing unnecessary constants and direct `true` returns. This change improves **code maintainability** by reducing duplication without altering any runtime behavior or introducing any functional impact.

This commit introduces a **new performance tracking capability** for the **React Native renderer**, providing detailed insights into rendering operations within **React Native DevTools performance traces**. It instruments key parts of the rendering pipeline, specifically adding `PerformanceTracer.trace` calls to the **Android `MountItemDispatcher`** for view commands, pre-mount, and mount item execution. Concurrently, the **C++ `ShadowTree::tryCommit` method** is instrumented with `PerformanceTracerSection` to track commit and layout operations, including metadata about the commit source. This **instrumentation** significantly enhances the **developer experience** by allowing developers to visualize the timing and flow of core rendering processes on a dedicated "Renderer" track, thereby improving the ability to diagnose and optimize UI performance. Supporting changes include updating JNI library references and adding `reactJsInspectorTracing` as a dependency.

This commit introduces a **critical compatibility fix** for **Apple platforms** by modifying the **`HighResTimeStamp`** implementation to use `mach_absolute_time()` instead of `std::chrono::steady_clock`. Previously, `steady_clock` included device sleep time, leading to inconsistencies with native iOS system APIs like `UITouch.timestamp` and `NSProcessInfo.processInfo.systemUptime`. This change, primarily within the **`react/timing` subsystem** and `RCTConversions.h`, ensures that all timestamps are now **accurate and consistent** with the platform's native clock domain. This **enhancement** resolves timing discrepancies, improving **performance logging** and interactions with system APIs. The `RCTHighResTimeStampFromSeconds()` function was also simplified, and documentation was updated to reflect this platform-specific clock behavior.

This commit introduces a **new feature flag**, `enableMutationObserverByDefault`, to enable the **experimental and partial implementation of the `MutationObserver` Web API** within React Native. This **new capability** allows for a controlled rollout, ensuring the `MutationObserver` module is only loaded and initialized when explicitly enabled. The changes involve integrating the flag across the **React Native feature flag system** (Java/Kotlin, C++, and JavaScript), updating **build configurations** for both Android and iOS to include the `MutationObserver` sources, and conditionally registering the `NativeMutationObserver` module in `DefaultTurboModules.cpp`. This provides developers with an opt-in mechanism to test this new functionality without impacting existing projects by default.

This commit introduces **new helper functions** to streamline **performance event tracing** within the **React Native Developer Tools (RNDT)** ecosystem. It adds overloaded `trace` methods to the **Kotlin `PerformanceTracer` class** for automatically timing code blocks using a try/finally pattern, and a **C++ `PerformanceTracerSection` RAII class** that reports timing upon scope exit. This **feature addition** simplifies the instrumentation of performance events across both Android-specific and core C++ components, improving the ease and reliability of collecting detailed performance data for RNDT.

This commit introduces a **new capability** by adding **performance tracking instrumentation** to the React Native renderer, enhancing visibility into rendering operations within React Native DevTools. Specifically, it instruments the **Android `MountItemDispatcher`** to trace view commands, premount, and mount operations, and the **C++ `ShadowTree::tryCommit`** method to track commit and layout operations. These new traces will appear on a dedicated "Renderer" track within the "⚛ Native" track group in DevTools, providing crucial insights for debugging and optimizing rendering performance. The instrumentation also includes metadata, such as the source of the commit, to further aid analysis.

This commit **enhances the Fabric event dispatching system** by formalizing event timestamps and propagating them accurately from the host platform (Android and iOS) to JavaScript. It introduces `HighResTimeStamp` across the **React Native core event infrastructure**, including `EventEmitterWrapper`, `FabricUIManager`, and `UIManagerBinding`, ensuring that events carry their native creation time rather than the time they reach JS. This **feature enhancement and refactoring** addresses issues with native event dispatch delay and normalizes event timing across various APIs, such as the `Event Timing API`. The change provides **more precise event timing information** for developers, improving the accuracy of performance metrics and user experience analysis. A notable aspect is the implementation of **clock correction on iOS** to reconcile `UITouch` timestamps with the C++ clock.

This commit **adds new integration tests** to validate recent changes in the **React Native renderer's event dispatching mechanism**. Specifically, it verifies that event objects are correctly exposed in the global scope during dispatch and that event timestamps are accurately read from native sources, falling back to `performance.now()` when necessary. This **maintenance work** enhances the **robustness and correctness** of event handling by providing comprehensive test coverage for critical event properties within the `EventDispatching` module, ensuring reliable event processing for all React Native applications.

This commit **refactors** the **`FrameTimingsObserver`** within React Native's **Android dev support** to enable robust frame timing tracking across multiple activities. Previously, frame timing observation would break when navigating between different activities; now, the observer dynamically updates its associated `Window` via a new `setCurrentWindow()` method. This **refactoring**, integrated by **`ReactHostImpl`** during host lifecycle events, ensures **continuous and accurate frame timing observation** in multi-activity Android applications, preventing data loss and improving performance monitoring.

This commit introduces a **new capability** to the **frame timing trace** mechanism within **React Native's developer support tools**, ensuring a more complete record of UI performance. It now captures an initial screenshot immediately when `start()` is called, addressing a previous limitation where the initial UI state was missing from traces if no subsequent UI changes occurred. This enhancement provides a more accurate and comprehensive visual context for **performance analysis** by guaranteeing at least one frame is recorded at the trace's beginning. Additionally, the commit **refactors** the frame emission logic in `FrameTimingsObserver.kt` into a shared `emitFrameTiming()` method, reducing code duplication and improving maintainability.

This commit **fixes a compilation error** within the **React Native animated backend** by adding a missing include for `AnimatedPropsBuilder.h` to `NativeAnimatedNodesManager.h`. This **maintenance fix** resolves an issue where the binary failed to compile because `AnimatedPropsBuilder` was undefined, particularly when the `RN_USE_ANIMATION_BACKEND` flag was enabled. The change ensures that the **animation subsystem** compiles correctly, preventing build failures that were impacting internal Fantom tests and improving overall project stability.

This commit performs a **refactoring** by **removing unnecessary catch bindings** across several modules within the `react-native` package. Specifically, it cleans up error handling in areas such as **React DevTools setup** (`setUpReactDevTools.js`), **XMLHttpRequest processing** (`XMLHttpRequest.js`), **Hot Module Replacement (HMR)** (`HMRClient.js`), and **safe stringification utilities** (`stringifySafe.js`). This **code quality improvement** removes unused error variables from `catch` blocks, enhancing readability and slightly optimizing the codebase without altering any functional behavior. The change is a broad **codemod** applied to improve the overall maintainability of the project.

This commit **refactors error handling** across **React Native's JavaScript codebase** by updating `try/catch` blocks to use `unknown` type annotations for caught exceptions. It introduces new utility functions, `toError` and `toExtendedError`, to consistently convert unknown values into `Error` or `ExtendedError` instances, respectively. These changes are applied to critical modules like `JSTimers`, `InteractionManager`, and **LogBox**, enhancing **type safety and consistency** in exception processing. The work ensures better Flow type compatibility and more robust error reporting within the framework.

This commit performs a **cleanup and refactoring** by **removing the `enableWebPerformanceAPIsByDefault` feature flag** from the React Native codebase. This flag, which previously controlled the availability of **Web Performance APIs** like Performance Timeline and User Timings, is no longer needed as these APIs are now **always enabled by default**. The change impacts various parts of the **React Native Android** and **React Native Common (C++)** feature flag infrastructure, including `ReactNativeFeatureFlags` and `ReactNativeFeatureFlagsAccessor`, and ensures the `NativePerformance` module is unconditionally available. This **maintenance** task simplifies the codebase and guarantees consistent access to performance tooling for all applications.

This commit introduces a **refactoring** to the **`RCTDeviceEventEmitter`** module, specifically within its `emit` method. It now utilizes a `try...finally` block to ensure that the `endEvent` call, crucial for **performance measurement**, is always executed. This change enhances the **robustness of performance profiling timespans** for **device events**, preventing them from being interrupted or corrupted if an exception occurs within one of the event listeners. The primary goal is to maintain the integrity of performance metrics by guaranteeing proper event termination.