Function inspectHooksOfFiber

packages/react-debug-tools/src/ReactDebugHooks.js:1298–1392

(
  fiber: Fiber,
  currentDispatcher: ?CurrentDispatcherRef,
)

}

export function inspectHooksOfFiber(
  fiber: Fiber,
  currentDispatcher: ?CurrentDispatcherRef,
): HooksTree {
  // DevTools will pass the current renderer's injected dispatcher.
  // Other apps might compile debug hooks as part of their app though.
  if (currentDispatcher == null) {
    currentDispatcher = ReactSharedInternals;
  }

  if (
    fiber.tag !== FunctionComponent &&
    fiber.tag !== SimpleMemoComponent &&
    fiber.tag !== ForwardRef
  ) {
    throw new Error(
      'Unknown Fiber. Needs to be a function component to inspect hooks.',
    );
  }

  // Warm up the cache so that it doesn't consume the currentHook.
  getPrimitiveStackCache();

  // Set up the current hook so that we can step through and read the
  // current state from them.
  currentHook = (fiber.memoizedState: Hook);
  currentFiber = fiber;
  const thenableState =
    fiber.dependencies && fiber.dependencies._debugThenableState;
  // In DEV the thenableState is an inner object.
  const usedThenables: any = thenableState
    ? thenableState.thenables || thenableState
    : null;
  currentThenableState = Array.isArray(usedThenables) ? usedThenables : null;
  currentThenableIndex = 0;

  if (hasOwnProperty.call(currentFiber, 'dependencies')) {
    // $FlowFixMe[incompatible-use]: Flow thinks hasOwnProperty might have nulled `currentFiber`
    const dependencies = currentFiber.dependencies;
    currentContextDependency =
      dependencies !== null ? dependencies.firstContext : null;
  } else if (hasOwnProperty.call(currentFiber, 'dependencies_old')) {
    const dependencies: Dependencies = (currentFiber: any).dependencies_old;
    currentContextDependency =
      dependencies !== null ? dependencies.firstContext : null;
  } else if (hasOwnProperty.call(currentFiber, 'dependencies_new')) {
    const dependencies: Dependencies = (currentFiber: any).dependencies_new;
    currentContextDependency =
      dependencies !== null ? dependencies.firstContext : null;
  } else if (hasOwnProperty.call(currentFiber, 'contextDependencies')) {
    const contextDependencies = (currentFiber: any).contextDependencies;
    currentContextDependency =
      contextDependencies !== null ? contextDependencies.first : null;
  } else {
    throw new Error(
      'Unsupported React version. This is a bug in React Debug Tools.',
    );
  }