react/packages/shared/ReactFeatureFlags.js
Andrew Clark 87ae211ccd
New context API (#11818)
* New context API

Introduces a declarative context API that propagates updates even when
shouldComponentUpdate returns false.

* Fuzz tester for context

* Use ReactElement for provider and consumer children

* Unify more branches in createFiberFromElement

* Compare context values using Object.is

Same semantics as PureComponent/shallowEqual.

* Add support for Provider and Consumer to server-side renderer

* Store providers on global stack

Rather than using a linked list stored on the context type. The global
stack can be reset in case of an interruption or error, whereas with the
linked list implementation, you'd need to keep track of every
context type.

* Put new context API behind a feature flag

We'll enable this in www only for now.

* Store nearest provider on context object

* Handle reentrancy in server renderer

Context stack should be per server renderer instance.

* Bailout of consumer updates using bitmask

The context type defines an optional function that compares two context
values, returning a bitfield. A consumer may specify the bits it needs
for rendering. If a provider's context changes, and the consumer's bits
do not intersect with the changed bits, we can skip the consumer.

This is similar to how selectors are used in Redux but fast enough to do
while scanning the tree. The only user code involved is the function
that computes the changed bits. But that's only called once per provider
update, not for every consumer.

* Store current value and changed bits on context object

There are fewer providers than consumers, so better to do this work
at the provider.

* Use maximum of 31 bits for bitmask

This is the largest integer size in V8 on 32-bit systems. Warn in
development if too large a number is used.

* ProviderComponent -> ContextProvider, ConsumerComponent -> ContextConsumer

* Inline Object.is

* Warn if multiple renderers concurrently render the same context provider

Let's see if we can get away with not supporting this for now. If it
turns out that it's needed, we can fall back to backtracking the
fiber return path.

* Nits that came up during review
2018-01-24 19:36:22 -08:00

36 lines
1.1 KiB
JavaScript

/**
* Copyright (c) 2013-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @flow
*/
import invariant from 'fbjs/lib/invariant';
export const enableAsyncSubtreeAPI = true;
// Exports ReactDOM.createRoot
export const enableCreateRoot = false;
export const enableUserTimingAPI = __DEV__;
// Mutating mode (React DOM, React ART, React Native):
export const enableMutatingReconciler = true;
// Experimental noop mode (currently unused):
export const enableNoopReconciler = false;
// Experimental persistent mode (Fabric):
export const enablePersistentReconciler = false;
// Support for new context API
export const enableNewContextAPI = false;
// Helps identify side effects in begin-phase lifecycle hooks and setState reducers:
export const debugRenderPhaseSideEffects = false;
// Warn about deprecated, async-unsafe lifecycles; relates to RFC #6:
export const warnAboutDeprecatedLifecycles = false;
// Only used in www builds.
export function addUserTimingListener() {
invariant(false, 'Not implemented.');
}