React Source code: What does it mean by "real internal dependencies"

Question

I was browsing the React source code and noticed ReactDOMFiberFBEntry.js.

This file has the following comment:

 // These are real internal dependencies that are trickier to remove:

What does it mean by "real internal dependencies" Internal to react itself, the React Dom? I'm sure this is blindingly obvious but i'm not quite sure. Also does the word "real" have much meaning in this case?

source:

/**
 * Copyright 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

'use strict';

var ReactDOMFiber = require('ReactDOMFiberEntry');

Object.assign(
  ReactDOMFiber.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED,
  {
    // These are real internal dependencies that are trickier to remove:
    ReactBrowserEventEmitter: require('ReactBrowserEventEmitter'),
    ReactErrorUtils: require('ReactErrorUtils'),
    ReactFiberErrorLogger: require('ReactFiberErrorLogger'),
    ReactFiberTreeReflection: require('ReactFiberTreeReflection'),
    ReactDOMComponentTree: require('ReactDOMComponentTree'),
    ReactInstanceMap: require('ReactInstanceMap'),
    // This is used for ajaxify on www:
    DOMProperty: require('DOMProperty'),
    // These are dependencies of TapEventPlugin:
    EventPluginUtils: require('EventPluginUtils'),
    EventPropagators: require('EventPropagators'),
    SyntheticUIEvent: require('SyntheticUIEvent'),
  },
);

module.exports = ReactDOMFiber;

Answer 1

As noted by Dan Abramov, the __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED object contains React internal functions and states. Those internals are not intended to be used from the React public APIs.

Dan wrote about it:

No, it’s not safe to use. That’s why it has a scary name. We offer no guarantees about what will happen if you access things there. The behavior can change on any release. We strongly recommend against touching it in your library if you don’t want that library to break later.