@react-navigation/core/lib/module/EnsureSingleNavigator.js

import * as React from 'react';
const MULTIPLE_NAVIGATOR_ERROR = `Another navigator is already registered for this container. You likely have multiple navigators under a single "NavigationContainer" or "Screen". Make sure each navigator is under a separate "Screen" container. See https://reactnavigation.org/docs/nesting-navigators for a guide on nesting.`;
export const SingleNavigatorContext = /*#__PURE__*/React.createContext(undefined);
/**
 * Component which ensures that there's only one navigator nested under it.
 */

export default function EnsureSingleNavigator(_ref) {
  let {
    children
  } = _ref;
  const navigatorKeyRef = React.useRef();
  const value = React.useMemo(() => ({
    register(key) {
      const currentKey = navigatorKeyRef.current;

      if (currentKey !== undefined && key !== currentKey) {
        throw new Error(MULTIPLE_NAVIGATOR_ERROR);
      }

      navigatorKeyRef.current = key;
    },

    unregister(key) {
      const currentKey = navigatorKeyRef.current;

      if (key !== currentKey) {
        return;
      }

      navigatorKeyRef.current = undefined;
    }

  }), []);
  return /*#__PURE__*/React.createElement(SingleNavigatorContext.Provider, {
    value: value
  }, children);
}
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