Function warnForMissingKey

packages/react-server/src/ReactFizzServer.js:3665–3757

(request: Request, task: Task, child: mixed)

}

function warnForMissingKey(request: Request, task: Task, child: mixed): void {
  if (__DEV__) {
    if (
      child === null ||
      typeof child !== 'object' ||
      (child.$$typeof !== REACT_ELEMENT_TYPE &&
        child.$$typeof !== REACT_PORTAL_TYPE)
    ) {
      return;
    }

    if (
      !child._store ||
      ((child._store.validated || child.key != null) &&
        child._store.validated !== 2)
    ) {
      return;
    }

    if (typeof child._store !== 'object') {
      throw new Error(
        'React Component in warnForMissingKey should have a _store. ' +
          'This error is likely caused by a bug in React. Please file an issue.',
      );
    }

    // $FlowFixMe[cannot-write] unable to narrow type from mixed to writable object
    child._store.validated = 1;

    let didWarnForKey = request.didWarnForKey;
    if (didWarnForKey == null) {
      didWarnForKey = request.didWarnForKey = new WeakSet();
    }
    const parentStackFrame = task.componentStack;
    if (parentStackFrame === null || didWarnForKey.has(parentStackFrame)) {
      // We already warned for other children in this parent.
      return;
    }
    didWarnForKey.add(parentStackFrame);

    const componentName = getComponentNameFromType(child.type);
    const childOwner = child._owner;
    const parentOwner = parentStackFrame.owner;

    let currentComponentErrorInfo = '';
    if (parentOwner && typeof parentOwner.type !== 'undefined') {
      const name = getComponentNameFromType(parentOwner.type);
      if (name) {
        currentComponentErrorInfo =
          '\n\nCheck the render method of `' + name + '`.';
      }
    }
    if (!currentComponentErrorInfo) {
      if (componentName) {
        currentComponentErrorInfo = `\n\nCheck the top-level render call using <${componentName}>.`;
      }
    }