Function validateFragmentProps

packages/react-reconciler/src/ReactChildFiber.js:230–276

(
  element: ReactElement,
  fiber: null | Fiber,
  returnFiber: Fiber,
)

// We do this here instead of BeginWork because the Fragment fiber doesn't have
// the whole props object, only the children and is shared with arrays.
function validateFragmentProps(
  element: ReactElement,
  fiber: null | Fiber,
  returnFiber: Fiber,
) {
  if (__DEV__) {
    const keys = Object.keys(element.props);
    for (let i = 0; i < keys.length; i++) {
      const key = keys[i];
      if (
        key !== 'children' &&
        key !== 'key' &&
        (enableFragmentRefs ? key !== 'ref' : true)
      ) {
        if (fiber === null) {
          // For unkeyed root fragments without refs (enableFragmentRefs),
          // there's no Fiber. We create a fake one just for error stack handling.
          fiber = createFiberFromElement(element, returnFiber.mode, 0);
          if (__DEV__) {
            fiber._debugInfo = currentDebugInfo;
          }
          fiber.return = returnFiber;
        }
        runWithFiberInDEV(
          fiber,
          erroredKey => {
            if (enableFragmentRefs) {
              console.error(
                'Invalid prop `%s` supplied to `React.Fragment`. ' +
                  'React.Fragment can only have `key`, `ref`, and `children` props.',
                erroredKey,
              );
            } else {
              console.error(
                'Invalid prop `%s` supplied to `React.Fragment`. ' +
                  'React.Fragment can only have `key` and `children` props.',
                erroredKey,
              );
            }
          },
          key,
        );
        break;
      }
    }
  }
}

function unwrapThenable<T>(thenable: Thenable<T>): T {
  const index = thenableIndexCounter;