ReactFiberLegacyContext.js — react Source File

Source Code

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */

import type {Fiber} from './ReactInternalTypes';
import type {StackCursor} from './ReactFiberStack';

import {disableLegacyContext} from 'shared/ReactFeatureFlags';
import {ClassComponent, HostRoot} from './ReactWorkTags';
import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';

import {createCursor, push, pop} from './ReactFiberStack';

let warnedAboutMissingGetChildContext;

if (__DEV__) {
  warnedAboutMissingGetChildContext = ({}: {[string]: boolean});
}

export const emptyContextObject: {} = {};
if (__DEV__) {
  Object.freeze(emptyContextObject);
}

// A cursor to the current merged context object on the stack.
const contextStackCursor: StackCursor<Object> =
  createCursor(emptyContextObject);
// A cursor to a boolean indicating whether the context has changed.
const didPerformWorkStackCursor: StackCursor<boolean> = createCursor(false);
// Keep track of the previous context object that was on the stack.
// We use this to get access to the parent context after we have already
// pushed the next context provider, and now need to merge their contexts.
let previousContext: Object = emptyContextObject;

function getUnmaskedContext(
  workInProgress: Fiber,
  Component: Function,
  didPushOwnContextIfProvider: boolean,
): Object {
  if (disableLegacyContext) {
    return emptyContextObject;
  } else {
    if (didPushOwnContextIfProvider && isContextProvider(Component)) {
      // If the fiber is a context provider itself, when we read its context
      // we may have already pushed its own child context on the stack. A context
      // provider should not "see" its own child context. Therefore we read the
      // previous (parent) context instead for a context provider.
      return previousContext;
    }
    return contextStackCursor.current;
  }
}

function cacheContext(
  workInProgress: Fiber,
// ... (265 more lines)