Function ReactFiberLegacyContext

code/new-context-api/public/app.js:11642–11863

(stack)

}

var ReactFiberLegacyContext = function (stack) {
  var createCursor = stack.createCursor,
      push = stack.push,
      pop = stack.pop;

  // A cursor to the current merged context object on the stack.

  var contextStackCursor = createCursor(emptyObject);
  // A cursor to a boolean indicating whether the context has changed.
  var didPerformWorkStackCursor = 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.
  var previousContext = emptyObject;

  function getUnmaskedContext(workInProgress) {
    var hasOwnContext = isContextProvider(workInProgress);
    if (hasOwnContext) {
      // If the fiber is a context provider itself, when we read its context
      // we 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, unmaskedContext, maskedContext) {
    var instance = workInProgress.stateNode;
    instance.__reactInternalMemoizedUnmaskedChildContext = unmaskedContext;
    instance.__reactInternalMemoizedMaskedChildContext = maskedContext;
  }

  function getMaskedContext(workInProgress, unmaskedContext) {
    var type = workInProgress.type;
    var contextTypes = type.contextTypes;
    if (!contextTypes) {
      return emptyObject;
    }

    // Avoid recreating masked context unless unmasked context has changed.
    // Failing to do this will result in unnecessary calls to componentWillReceiveProps.
    // This may trigger infinite loops if componentWillReceiveProps calls setState.
    var instance = workInProgress.stateNode;
    if (instance && instance.__reactInternalMemoizedUnmaskedChildContext === unmaskedContext) {
      return instance.__reactInternalMemoizedMaskedChildContext;
    }

    var context = {};
    for (var key in contextTypes) {
      context[key] = unmaskedContext[key];
    }

    {
      var name = getComponentName(workInProgress) || 'Unknown';
      checkPropTypes(contextTypes, context, 'context', name, ReactDebugCurrentFiber.getCurrentFiberStackAddendum);
    }