Ruslan Lesiutin

This commit introduces a **new feature** to the **React DevTools Components panel**, enabling it to display the full subtree of **Activity components**. When an Activity component is in a hidden mode, its entire subtree will now be visually dimmed in the DevTools UI, providing clearer state indication. This enhancement involves backend logic in `renderer.js` to propagate hidden states, updates to the frontend `store.js` for tracking, and rendering changes in the `Element.js` component to apply the dimming effect. It significantly improves the debugging experience for applications utilizing Activity components by offering better visibility into their structure and hidden status, with new tests and a sandbox case added to `react-devtools-shell` for validation.

This commit performs a **refactoring** within the **React DevTools backend** to enhance code organization and maintainability. It **extracts the `getInternalReactConstants` function**, along with its associated types and constants, from `packages/react-devtools-shared/src/backend/fiber/renderer.js`. This logic is now centralized in a new, dedicated shared module: `packages/react-devtools-shared/src/backend/fiber/shared/DevToolsFiberInternalReactConstants.js`. This **code organization** effort improves modularity for how DevTools interacts with React's internal structures, making this critical logic easier to manage and test. The change has no impact on DevTools' external functionality, but significantly cleans up the internal **fiber renderer integration** code.

This commit **refines** the **infinite render loop detection** mechanism within the **React reconciler**, specifically when the `enableInfiniteRenderLoopDetection` feature flag is active. It modifies `ReactFiberWorkLoop.js` to now issue a **console warning** for potential infinite update loops, instead of throwing an error and interrupting the render. This **maintenance** change addresses observed false positives and allows for better signal gathering without crashing applications, while preserving the original error-throwing behavior when the flag is disabled. Users with the flag enabled will now see warnings instead of errors, improving debugging without interrupting the user experience. Tests in `ReactUpdates-test.js` have been updated to reflect this new warning behavior.

This commit implements a **bug fix** within the **React DevTools** to prevent an empty "Suspended By" section from rendering. It modifies the `InspectedElementSuspendedBy` component in `packages/react-devtools-shared/src/devtools/views/Components/InspectedElementSuspendedBy.js` to explicitly return `null` if no suspended groups are present. This **UI improvement** ensures that the section only appears when relevant data exists, thereby cleaning up the interface and enhancing the user experience by removing unnecessary visual clutter.

This commit performs a significant **refactoring** of the **React DevTools backend** by extracting numerous pure utility functions and type definitions from the core `packages/react-devtools-shared/src/backend/fiber/renderer.js` module. This **maintenance** effort introduces several new, specialized shared modules, including `DevToolsNativeHost.js` for native environment utilities, `DevToolsFiberChangeDetection.js` for fiber change detection, `DevToolsFiberInspection.js` for inspection utilities, and `DevToolsFiberSuspense.js` for Suspense-related logic. The goal is to improve the **modularity and reusability** of the DevTools backend codebase, making it easier to maintain and extend in the future. This change primarily impacts the internal structure of the **DevTools fiber renderer implementation**.

This commit **removes the `enableHiddenSubtreeInsertionEffectCleanup` feature flag** from the **React Reconciler**, as the functionality it controlled has been stable and enabled in production for an extended period. This **refactoring** effort simplifies the **commit phase** logic by making the `commitHookEffectListUnmount` call unconditional during deletion effects, thereby standardizing the behavior for **effect cleanup** when hidden subtrees are inserted. The change eliminates conditional compilation paths, streamlining the codebase. Test assertions across `ReactHooksWithNoopRenderer-test.js`, `ReactSuspenseEffectsSemantics-test.js`, and `useEffectEvent-test.js` are updated to reflect this unconditional behavior, ensuring consistent and simplified codebase maintenance without altering existing runtime semantics for users.

This commit implements a **maintenance fix** by **removing an unused variable** from the codebase. This action directly addresses a **linter warning**, improving overall **code quality** and adherence to coding standards. The change ensures a cleaner and more maintainable codebase, preventing potential confusion and reducing noise from static analysis tools.

This commit introduces a **bug fix** within the **React DevTools shared store logic** to prevent incorrect removal of suspense child nodes. Previously, the `_onCommitFiberUnmount` function in `packages/react-devtools-shared/src/devtools/store.js` could silently remove the wrong child from `parentSuspense.children` if the intended child was not present. The change adds a crucial check to verify the presence of the suspense child node in its parent's children array before attempting removal, now throwing an error if it's not found. This ensures the **DevTools' internal state management** remains accurate and robust when handling **Suspense components**, preventing misleading component tree representations.

This commit performs **code cleanup** within the **DevTools** module by **removing the experimental `__IS_INTERNAL_MCP_BUILD__` flag** and all associated code. As this flag was explicitly marked as unused, its removal simplifies the codebase and eliminates dead code, contributing to better maintainability. This **maintenance** task has no functional impact on DevTools features, as the removed code path was never active.

This commit delivers a **bug fix** for the **React DevTools profiler**, specifically addressing an issue where profiling durations were incorrectly captured for fibers within **disconnected subtrees**. Previously, this could lead to "Could not clone the node" errors on the frontend, particularly during complex scenarios like **Suspense transitions** from fallback to content. The fix modifies the `attach` function within `packages/react-devtools-shared/src/backend/fiber/renderer.js` to prevent `recordProfilingDurations()` from being called for these unattached fibers. This ensures that the **profiling data** remains consistent and accurate, preventing crashes and improving the reliability of the **DevTools** when analyzing component lifecycles.

This commit delivers a **bug fix** for **React DevTools** to eliminate **false-positive re-render reports** in profiling charts and re-render highlighting. Previously, DevTools would incorrectly indicate re-renders for components that were descendants of filtered-out nodes, even when no actual rendering occurred. The solution involves modifying the `attach` function within `packages/react-devtools-shared/src/backend/fiber/renderer.js` to add validation, ensuring `prevFiber` is distinct from `nextFiber` before evaluating `didFiberRender`. This significantly enhances the **accuracy of re-render detection and profiling data** within DevTools, and new **tests** in `profilingCharts-test.js` were added to confirm the fix.

This commit introduces a **validation check** within the **React DevTools Profiler panel** to prevent silent errors during trace serialization. Specifically, the `getClonedNode` function in `packages/react-devtools-shared/src/devtools/views/Profiler/CommitTreeBuilder.js` will now **throw an error** if an attempt is made to clone a node that does not exist. This **bug fix** addresses an issue where `TREE_OPERATION_UPDATE_TREE_BASE_DURATION` could precede `TREE_OPERATION_ADD`, leading to the creation of empty, non-existent nodes, thereby improving the robustness and error reporting of the profiler's tree reconstruction logic.

This commit delivers a crucial **bug fix** for the **React DevTools Profiler**, specifically addressing an issue where switching between different profiler roots would cause an "Invalid commit X. There are only Y commits." error. The problem stemmed from the commit index not being reset, leading to out-of-bounds access when a new root had fewer commits than the previously selected index. This **fix** now **resets the selected commit index to 0** (or `null` if no commits exist) within `useCommitFilteringAndNavigation.js` whenever the profiler's commit data changes, significantly **improving the stability and user experience** of the DevTools flamegraph navigation.

This commit **refactors** the **React feature flag system** by making the `enableComponentPerformanceTrack` flag statically `true` across all environments, including the `native-fb` and `www` forks. Previously, this flag was either conditionally enabled based on `__PROFILE__` or destructured from dynamic flags, introducing unnecessary complexity. This **maintenance** change **simplifies the management** of component performance tracking, ensuring it is consistently active whenever the broader `enableProfilerTimer` (which is already gated by `__PROFILE__`) is enabled. The update streamlines internal flag logic, contributing to a more unified and predictable approach for performance-related feature flags within the project.

This commit **removes the feature flag** that previously gated the `REACT_ELEMENT_TYPE` symbol, making the `react.transitional.element` symbol **permanently enabled by default**. This **refactoring and cleanup** effort simplifies the definition within **React core symbols** in `packages/shared/ReactSymbols.js` by directly assigning the new symbol and eliminating conditional logic. A corresponding **test case** in `packages/react-dom/src/__tests__/ReactDOMOption-test.js` is updated to reflect this change, removing the feature flag gate. The change signifies the full adoption of the new element symbol, streamlining the internal representation of React elements across the project.

This commit introduces a **bug fix** within the **React DevTools shared backend**, specifically affecting the `Highlighter` view. It **refines the document availability check** in the `setupHighlighter` function by replacing a direct reference with a safer `typeof document === 'object'` check. This change prevents potential `ReferenceError` exceptions that could occur in environments where the global `document` object is unavailable. Ultimately, it **enhances the robustness and compatibility** of the DevTools highlighter, ensuring it operates reliably across diverse execution contexts.

This commit implements **feature checks** within the **React DevTools backend** to enhance the robustness of stack trace parsing. Specifically, it adds checks for `CallSite` methods used by the `collectStackTrace` function in `packages/react-devtools-shared/src/backend/utils/parseStackTrace.js`. This **bug fix** addresses compatibility issues with JavaScript runtimes that do not fully implement the non-standard `Error.prepareStackTrace` API. The change ensures more **reliable and compatible** stack trace reporting by gracefully handling variations in runtime implementations.

This commit introduces a **bug fix** to the **React DevTools** **highlighter logic**, specifically within `packages/react-devtools-shared/src/backend/views/Highlighter/index.js`. It modifies the `setupHighlighter` function to allow the visual overlay to be displayed even if the host environment, such as **React Native**, does not implement the `getClientRects` method. This change makes the DevTools backend more **host-agnostic**, ensuring the debugging overlay functions correctly across different platforms. The fix addresses an issue where the overlay would not appear in environments lacking CSS box model concepts, significantly improving the debugging experience for non-web applications.

This commit delivers a **bug fix** and **compatibility improvement** for the **React DevTools backend**, specifically addressing its behavior in **non-DOM environments**. It introduces **environment checks** within the `packages/react-devtools-shared/src/backend/views/Highlighter/index.js` module, making DOM-specific operations like `scrollIntoView` and `sendScroll` no-ops when running in **React Native**. This prevents errors and ensures **stability** by gracefully handling features designed for web environments, avoiding unexpected behavior for users debugging React Native applications. The change ensures the **Highlighter** component functions robustly across diverse React platforms.

This commit **adds new examples** for the `useSyncExternalStore` React hook to the **React DevTools Shell**. A new component, `UseSyncExternalStore.js`, is introduced within the `InspectableElements` section, showcasing various usage patterns like `SingleHookCase` and `HookTreeCase`. This **new capability** serves as a valuable **maintenance** and **debugging** tool, specifically designed to aid in **testing hook tree reconstruction logic** and **hook names parsing** features within DevTools. The examples provide concrete scenarios for verifying the correct behavior of these internal DevTools functionalities.