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[Fizz] Implement New Context (#21255)
* Add NewContext module This implements a reverse linked list tree containing the previous contexts. * Implement recursive algorithm This algorithm pops the contexts back to a shared ancestor on the way down the stack and then pushes new contexts in reverse order up the stack. * Move isPrimaryRenderer to ServerFormatConfig This is primarily intended to be used to support renderToString with a separate build than the main one. This allows them to be nested. * Wire up more element type matchers * Wire up Context Provider type * Wire up Context Consumer * Test * Implement reader in class * Update error codez
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,278 @@ | ||
| /** | ||
| * Copyright (c) Facebook, Inc. and its affiliates. | ||
| * | ||
| * This source code is licensed under the MIT license found in the | ||
| * LICENSE file in the root directory of this source tree. | ||
| * | ||
| * @flow | ||
| */ | ||
|
|
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| import type {ReactContext} from 'shared/ReactTypes'; | ||
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| import {isPrimaryRenderer} from './ReactServerFormatConfig'; | ||
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| import invariant from 'shared/invariant'; | ||
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| let rendererSigil; | ||
| if (__DEV__) { | ||
| // Use this to detect multiple renderers using the same context | ||
| rendererSigil = {}; | ||
| } | ||
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| // Used to store the parent path of all context overrides in a shared linked list. | ||
| // Forming a reverse tree. | ||
| type ContextNode<T> = { | ||
| parent: null | ContextNode<any>, | ||
| depth: number, // Short hand to compute the depth of the tree at this node. | ||
| context: ReactContext<T>, | ||
| parentValue: T, | ||
| value: T, | ||
| }; | ||
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| // The structure of a context snapshot is an implementation of this file. | ||
| // Currently, it's implemented as tracking the current active node. | ||
| export opaque type ContextSnapshot = null | ContextNode<any>; | ||
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| export const rootContextSnapshot: ContextSnapshot = null; | ||
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| // We assume that this runtime owns the "current" field on all ReactContext instances. | ||
| // This global (actually thread local) state represents what state all those "current", | ||
| // fields are currently in. | ||
| let currentActiveSnapshot: ContextSnapshot = null; | ||
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| function popNode(prev: ContextNode<any>): void { | ||
| if (isPrimaryRenderer) { | ||
| prev.context._currentValue = prev.parentValue; | ||
| } else { | ||
| prev.context._currentValue2 = prev.parentValue; | ||
| } | ||
| } | ||
|
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| function pushNode(next: ContextNode<any>): void { | ||
| if (isPrimaryRenderer) { | ||
| next.context._currentValue = next.value; | ||
| } else { | ||
| next.context._currentValue2 = next.value; | ||
| } | ||
| } | ||
|
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| function popToNearestCommonAncestor( | ||
| prev: ContextNode<any>, | ||
| next: ContextNode<any>, | ||
| ): void { | ||
| if (prev === next) { | ||
| // We've found a shared ancestor. We don't need to pop nor reapply this one or anything above. | ||
| } else { | ||
| popNode(prev); | ||
| const parentPrev = prev.parent; | ||
| const parentNext = next.parent; | ||
| if (parentPrev === null) { | ||
| invariant( | ||
| parentNext === null, | ||
| 'The stacks must reach the root at the same time. This is a bug in React.', | ||
| ); | ||
| } else { | ||
| invariant( | ||
| parentNext !== null, | ||
| 'The stacks must reach the root at the same time. This is a bug in React.', | ||
| ); | ||
| popToNearestCommonAncestor(parentPrev, parentNext); | ||
| // On the way back, we push the new ones that weren't common. | ||
| pushNode(next); | ||
| } | ||
| } | ||
| } | ||
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| function popAllPrevious(prev: ContextNode<any>): void { | ||
| popNode(prev); | ||
| const parentPrev = prev.parent; | ||
| if (parentPrev !== null) { | ||
| popAllPrevious(parentPrev); | ||
| } | ||
| } | ||
|
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| function pushAllNext(next: ContextNode<any>): void { | ||
| const parentNext = next.parent; | ||
| if (parentNext !== null) { | ||
| pushAllNext(parentNext); | ||
| } | ||
| pushNode(next); | ||
| } | ||
|
|
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| function popPreviousToCommonLevel( | ||
| prev: ContextNode<any>, | ||
| next: ContextNode<any>, | ||
| ): void { | ||
| popNode(prev); | ||
| const parentPrev = prev.parent; | ||
| invariant( | ||
| parentPrev !== null, | ||
| 'The depth must equal at least at zero before reaching the root. This is a bug in React.', | ||
| ); | ||
| if (parentPrev.depth === next.depth) { | ||
| // We found the same level. Now we just need to find a shared ancestor. | ||
| popToNearestCommonAncestor(parentPrev, next); | ||
| } else { | ||
| // We must still be deeper. | ||
| popPreviousToCommonLevel(parentPrev, next); | ||
| } | ||
| } | ||
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| function popNextToCommonLevel( | ||
| prev: ContextNode<any>, | ||
| next: ContextNode<any>, | ||
| ): void { | ||
| const parentNext = next.parent; | ||
| invariant( | ||
| parentNext !== null, | ||
| 'The depth must equal at least at zero before reaching the root. This is a bug in React.', | ||
| ); | ||
| if (prev.depth === parentNext.depth) { | ||
| // We found the same level. Now we just need to find a shared ancestor. | ||
| popToNearestCommonAncestor(prev, parentNext); | ||
| } else { | ||
| // We must still be deeper. | ||
| popNextToCommonLevel(prev, parentNext); | ||
| } | ||
| pushNode(next); | ||
| } | ||
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| // Perform context switching to the new snapshot. | ||
| // To make it cheap to read many contexts, while not suspending, we make the switch eagerly by | ||
| // updating all the context's current values. That way reads, always just read the current value. | ||
| // At the cost of updating contexts even if they're never read by this subtree. | ||
| export function switchContext(newSnapshot: ContextSnapshot): void { | ||
| // The basic algorithm we need to do is to pop back any contexts that are no longer on the stack. | ||
| // We also need to update any new contexts that are now on the stack with the deepest value. | ||
| // The easiest way to update new contexts is to just reapply them in reverse order from the | ||
| // perspective of the backpointers. To avoid allocating a lot when switching, we use the stack | ||
| // for that. Therefore this algorithm is recursive. | ||
| // 1) First we pop which ever snapshot tree was deepest. Popping old contexts as we go. | ||
| // 2) Then we find the nearest common ancestor from there. Popping old contexts as we go. | ||
| // 3) Then we reapply new contexts on the way back up the stack. | ||
| const prev = currentActiveSnapshot; | ||
| const next = newSnapshot; | ||
| if (prev !== next) { | ||
| if (prev === null) { | ||
| // $FlowFixMe: This has to be non-null since it's not equal to prev. | ||
| pushAllNext(next); | ||
| } else if (next === null) { | ||
| popAllPrevious(prev); | ||
| } else if (prev.depth === next.depth) { | ||
| popToNearestCommonAncestor(prev, next); | ||
| } else if (prev.depth > next.depth) { | ||
| popPreviousToCommonLevel(prev, next); | ||
| } else { | ||
| popNextToCommonLevel(prev, next); | ||
| } | ||
| currentActiveSnapshot = next; | ||
| } | ||
| } | ||
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| export function pushProvider<T>( | ||
| context: ReactContext<T>, | ||
| nextValue: T, | ||
| ): ContextSnapshot { | ||
| let prevValue; | ||
| if (isPrimaryRenderer) { | ||
| prevValue = context._currentValue; | ||
| context._currentValue = nextValue; | ||
| if (__DEV__) { | ||
| if ( | ||
| context._currentRenderer !== undefined && | ||
| context._currentRenderer !== null && | ||
| context._currentRenderer !== rendererSigil | ||
| ) { | ||
| console.error( | ||
| 'Detected multiple renderers concurrently rendering the ' + | ||
| 'same context provider. This is currently unsupported.', | ||
| ); | ||
| } | ||
| context._currentRenderer = rendererSigil; | ||
| } | ||
| } else { | ||
| prevValue = context._currentValue2; | ||
| context._currentValue2 = nextValue; | ||
| if (__DEV__) { | ||
| if ( | ||
| context._currentRenderer2 !== undefined && | ||
| context._currentRenderer2 !== null && | ||
| context._currentRenderer2 !== rendererSigil | ||
| ) { | ||
| console.error( | ||
| 'Detected multiple renderers concurrently rendering the ' + | ||
| 'same context provider. This is currently unsupported.', | ||
| ); | ||
| } | ||
| context._currentRenderer2 = rendererSigil; | ||
| } | ||
| } | ||
| const prevNode = currentActiveSnapshot; | ||
| const newNode: ContextNode<T> = { | ||
| parent: prevNode, | ||
| depth: prevNode === null ? 0 : prevNode.depth + 1, | ||
| context: context, | ||
| parentValue: prevValue, | ||
| value: nextValue, | ||
| }; | ||
| currentActiveSnapshot = newNode; | ||
| return newNode; | ||
| } | ||
|
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| export function popProvider<T>(context: ReactContext<T>): ContextSnapshot { | ||
| const prevSnapshot = currentActiveSnapshot; | ||
| invariant( | ||
| prevSnapshot !== null, | ||
| 'Tried to pop a Context at the root of the app. This is a bug in React.', | ||
| ); | ||
| if (__DEV__) { | ||
| if (prevSnapshot.context !== context) { | ||
| console.error( | ||
| 'The parent context is not the expected context. This is probably a bug in React.', | ||
| ); | ||
| } | ||
| } | ||
| if (isPrimaryRenderer) { | ||
| prevSnapshot.context._currentValue = prevSnapshot.parentValue; | ||
| if (__DEV__) { | ||
| if ( | ||
| context._currentRenderer !== undefined && | ||
| context._currentRenderer !== null && | ||
| context._currentRenderer !== rendererSigil | ||
| ) { | ||
| console.error( | ||
| 'Detected multiple renderers concurrently rendering the ' + | ||
| 'same context provider. This is currently unsupported.', | ||
| ); | ||
| } | ||
| context._currentRenderer = rendererSigil; | ||
| } | ||
| } else { | ||
| prevSnapshot.context._currentValue2 = prevSnapshot.parentValue; | ||
| if (__DEV__) { | ||
| if ( | ||
| context._currentRenderer2 !== undefined && | ||
| context._currentRenderer2 !== null && | ||
| context._currentRenderer2 !== rendererSigil | ||
| ) { | ||
| console.error( | ||
| 'Detected multiple renderers concurrently rendering the ' + | ||
| 'same context provider. This is currently unsupported.', | ||
| ); | ||
| } | ||
| context._currentRenderer2 = rendererSigil; | ||
| } | ||
| } | ||
| return (currentActiveSnapshot = prevSnapshot.parent); | ||
| } | ||
|
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| export function getActiveContext(): ContextSnapshot { | ||
| return currentActiveSnapshot; | ||
| } | ||
|
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| export function readContext<T>(context: ReactContext<T>): T { | ||
| const value = isPrimaryRenderer | ||
| ? context._currentValue | ||
| : context._currentValue2; | ||
| return value; | ||
| } |
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