Jack Pope

This commit **integrates React Feature Flags** into **`eslint-plugin-react-hooks`**, enabling dynamic configuration of experimental linting options. It **extends the `ReactFeatureFlags` system** to define new flags for compiler behaviors and updates the build infrastructure to resolve these flags differently across environments like OSS and Facebook WWW. This **new capability** provides a controlled rollout mechanism for experimental features in the ESLint plugin, **unblocking their release** and enhancing the flag parsing logic to support string values.

This commit **enables the `enableViewTransition` feature flag** across several React Native build configurations. Specifically, it activates this flag for **native Facebook builds** (`ReactFeatureFlags.native-fb.js`) and their corresponding test renderers (`ReactFeatureFlags.test-renderer.native-fb.js`, `ReactFeatureFlags.test-renderer.www.js`). This **configuration change** ensures that the `enableViewTransition` capability is now available by default in these environments, facilitating the use of view transitions in **React Native applications within the Facebook ecosystem**. The change marks a broader rollout, making the feature static and enabled everywhere except for dynamic control in the main www build.

This commit provides a **bug fix** for two issues affecting **focus handling** within **React DOM bindings**, specifically impacting `setFocusIfFocusable` and **fragment refs**. It corrects scenarios where delegated focus events were not properly recognized by introducing a document-level event listener, and prevents incorrect focus shifts when an element is already focused by checking `document.activeElement` early. These changes ensure more reliable and predictable focus behavior, particularly in complex forms with nested focusable elements or when using `fragmentRef.focus()`.

This commit **enables several feature flags related to Fragment Refs** across various build configurations within the `ReactFeatureFlags` system. Specifically, `enableFragmentRefsInstanceHandles` is activated for all builds, while `enableFragmentRefsTextNodes` is enabled for **native-oss** and **test-renderer.www** environments. Additionally, `enableFragmentRefs` and `enableFragmentRefsScrollIntoView` are turned on for the **test-renderer.www** build. This **new capability** makes the advanced Fragment Refs functionality available for testing and development in these specific environments, paving the way for broader adoption.

This commit **stabilizes** the internal `unstable_reactFragments` property, renaming it to `reactFragments` across the codebase. This **refactoring** primarily affects the **React DOM bindings** (`ReactFiberConfigDOM.js`) and **React Native renderer** (`ReactFiberConfigFabric.js`), where this property is used to manage fragment handles on host nodes for Observer caching. Corresponding **React DOM tests** (`ReactDOMFragmentRefs-test.js`) are also updated to reflect the new stable name. This change signifies that the `reactFragments` handle is now considered production-ready, enabling the full rollout of the **Fragment Refs feature**.

This commit performs **minor refactoring and maintenance** within the **React DOM bindings**, specifically targeting `FragmentInstance` logic in `ReactFiberConfigDOM.js`. It improves the **efficiency** of `indexOfEventListener` and adds **early exit and active element handling** to `FragmentInstance.prototype.blur` and `blurActiveElementWithinFragment`. Additionally, variable names are clarified in `FragmentInstance.prototype.compareDocumentPosition`, enhancing code readability and maintainability for internal DOM operations. These changes are primarily **internal optimizations** and code cleanups, addressing TODOs and improving the robustness of DOM fragment handling.

This commit **enhances the React Reconciler's fragment instance handling** to explicitly notify `FragmentInstance` of added or removed `HostText` fibers (text nodes). This **preparatory change** aims for **completeness and future extensibility**, anticipating potential stateful fragment features that might interact with text. It modifies **commit logic in `ReactFiberCommitHostEffects.js` and `ReactFiberCommitWork.js`** to include `HostText` fibers when the `enableFragmentRefsTextNodes` feature flag is active, extending deletion and layout effects to them. While the **DOM and Fabric host configurations** (`ReactFiberConfigDOM.js`, `ReactFiberConfigFabric.js`) are updated to handle these notifications, they currently **early-return for text nodes**, preventing event listener or observer attachment. This ensures the core reconciler is ready for future fragment capabilities without immediately altering existing runtime behavior for text nodes in current host environments.

This commit **enhances the test suite** for **React's `FragmentInstance`** by introducing **additional fixtures** to validate behavior with **text nodes**. It specifically adds new test cases and container components within `fixtures/dom/src/components/fixtures/fragment-refs` to cover `compareDocumentPosition`, event handling, and `getRootNode` functionality when fragments contain text. This **new capability** in testing infrastructure ensures the correct interaction of these DOM APIs and event systems with complex fragment structures, building on previous `FragmentInstance` improvements. The `TextNodesCase` fixture is significantly expanded to include these new scenarios, alongside new container components like `CompareDocumentPositionFragmentContainer` and `EventFragmentContainer`.

This commit introduces **support for text nodes within `FragmentInstance` operations**, significantly enhancing the robustness of **React fragment refs**. It enables methods like `getClientRects` and `scrollIntoView` to correctly interact with fragments containing text nodes, either mixed with elements or text-only, by leveraging the DOM Range API. The **React DOM bindings** and **Reconciler** are updated to handle `HostText` nodes, while `focus` and `observeUsing` are adjusted with specific behaviors or warnings for text-only fragments. This **new capability** improves the reliability of fragment refs for developers, ensuring more consistent behavior across various content types, and is controlled by the `enableFragmentRefsTextNodes` feature flag.

This commit **fixes a `TypeError` crash** that occurred when a **`ViewTransition`** component was used as a direct child of **`SuspenseList`** with `revealOrder="together"`. The issue arose because `resetChildFibers` would nullify the `stateNode` for `ViewTransition`, which was not subsequently re-initialized in `completeWork`, leading to `Cannot read properties of null (reading 'autoName')`. The **`react-reconciler`** now correctly initializes the `stateNode` for `ViewTransition` in `ReactFiberBeginWork.js` if it is null, following the pattern established for `Offscreen` components. This **bug fix** enhances the stability and reliability of concurrent rendering features when combining `ViewTransition` with `SuspenseList`. A **new regression test** has been added in `ReactDOMViewTransition-test.js` to prevent future regressions.

This commit introduces **new reporting modes** (`missing-only`, `extra-only`, `all`, `off`) for the **React Compiler's exhaustive effect dependency validation**, providing granular control over how missing or extra dependencies are reported. This **new capability** enhances the compiler's diagnostic features, affecting the core **dependency validation logic** in `ValidateExhaustiveDependencies.ts` and its configuration. As part of this **integration**, the `extra-only` mode is temporarily enabled within the `eslint-plugin-react-hooks` to begin testing warnings for superfluous dependencies. Furthermore, a **bug fix** was applied to `manualMemoLoc` by adding null checks, improving the robustness of the validation process. This work prepares the compiler for future consolidation of dependency validation.

Upgrade nextjs for compiler playground (#35353)

This commit implements a **temporary compatibility fix** within the **React DOM bindings** to ensure the `internalInstanceKey` continues to be attached to DOM nodes. Specifically, in **development builds**, functions like `precacheFiberNode` and `detachDeletedInstance` in `ReactDOMComponentTree.js` are adjusted to conditionally manage this key. This prevents breaking existing **internal development tooling** that relies on this DOM attachment during ongoing experimentation with broader changes. The actual internal instance tracking remains handled by a private map, making this a targeted adjustment solely for dev tooling compatibility.

This commit **enhances the React Compiler's static analysis** by extending the `ValidateNoSetStateInEffects` pass to detect synchronous `setState` calls made indirectly through `useEffectEvent` functions. Previously, wrapping `setState` in a `useEffectEvent` and calling it within an effect could bypass the validation, leading to potential cascading renders. Now, the **compiler correctly identifies and flags these problematic patterns**, pointing the error to the `useEffectEvent` call site. This **improves the robustness of effect validation** within the **React Compiler**, ensuring developers adhere to best practices and avoid performance pitfalls when using `useEffectEvent` within **React effects**.

This commit introduces a **new capability** to enhance the **encapsulation** of React's internal instance handles and props within the **React DOM bindings**. To prevent external libraries from relying on or manipulating these internals, the `fiber` node and `props` object are now stored in an **internal map** instead of directly on DOM elements. This **architectural refactoring** is controlled by a new `enableInternalInstanceMap` **feature flag**, allowing for experimentation with this approach. The change primarily affects `ReactDOMComponentTree.js`, updating functions like `getInstanceFromNode` and `getFiberCurrentPropsFromNode` to use the new map-based storage, thereby improving the **stability and maintainability** of React's core.

This commit introduces a **new capability** to **React's Fragment Refs** by adding an `unstable_reactFragments` property to DOM nodes that are children of a ref-attached Fragment. This property, enabled by the `enableFragmentRefsInstanceHandles` feature flag, allows direct access to the `FragmentInstance` from a host node, impacting both **React DOM bindings** and **React Native renderer**. The primary use case is to **unblock efficient caching and reuse of IntersectionObserver instances**, as it now allows using the `FragmentInstance` as a key for callbacks, addressing a current limitation in `observeUsing`. This **enhancement** also opens up possibilities for **event handling** by enabling `event.target.unstable_reactFragments` for operations like `getClientRects`, providing a more direct handle when an event is dispatched by the Fragment itself. While adding some overhead during `FragmentInstance` creation and node tracking, this change significantly improves the interoperability of Fragments with host elements.

This commit **introduces a new `getClientRects` method** to the **Fabric `FragmentInstance.prototype`** within the `react-native-renderer`. This **new feature** allows for the collection of multiple client rectangles from child instances, acting as a substitute for multi-rect element handling in React Native where only `getBoundingClientRect` is currently available. It specifically addresses scenarios involving nested `Text` components by calling `getBoundingClientRect` on each top-level host child. This enhances the layout information available for **Fabric fragment instances**, improving compatibility and rendering accuracy for complex text structures.

This commit introduces a **new feature** to the **React Native Fabric renderer**, specifically enhancing how **fragment instances** are managed. It adds a `getRootNode` method to `FragmentInstance.prototype` in `ReactFiberConfigFabric.js`, enabling fragment instances to correctly retrieve their root node. This implementation mirrors the behavior of `getRootNode` in the DOM, ensuring consistency across rendering environments. The change is a foundational step for improved **root fragment handling** within Fabric, providing a more robust mechanism for identifying fragment boundaries.

This commit **improves the clarity and precision of lint error messages** within the **React Hooks ESLint plugin** for violations related to the `useEffectEvent` hook. It refines the guidance to explicitly state that `useEffectEvent` functions can only be called from "Effects and Effect Events" within the same component, providing more accurate context than the previous "from the same component" message. This **developer experience improvement** also corrects a grammatical error in the referenced variable message. The changes involve updating the `RulesOfHooks.ts` file to generate these new messages and adjusting corresponding test cases in `ESLintRulesOfHooks-test.js`, ensuring developers receive more actionable feedback when misusing this specific hook.

This commit **updates** the **`eslint-plugin-react-hooks`** to align with the promotion of `useEffectEvent` to a canary release. It **removes the `__EXPERIMENTAL__` gating** from the `ExhaustiveDeps` and `RulesOfHooks` ESLint rules, specifically for the `isUseEffectEventIdentifier` logic, and their associated tests. This **maintenance** change ensures that the ESLint plugin now **recognizes `useEffectEvent` by default**, enabling proper linting and testing for this hook without requiring experimental flags. Consequently, developers using these React Hooks ESLint rules will experience correct behavior and validation for `useEffectEvent` out-of-the-box.