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Make host context use null as empty and only error in dev (#25609)
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Makes it slightly more blazing.

No host config actually uses null as any useful and we use this as a
placeholder value anyway. It's also better for perf since it doesn't let
two different hidden classes pass around. It's also a magic place holder
that triggers error if we do try to access anything from it.
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sebmarkbage authored Nov 1, 2022
1 parent 5f7ef8c commit 8e69bc4
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Showing 3 changed files with 33 additions and 109 deletions.
37 changes: 15 additions & 22 deletions packages/react-reconciler/src/ReactFiberHostContext.new.js
Original file line number Diff line number Diff line change
Expand Up @@ -14,33 +14,26 @@ import type {Container, HostContext} from './ReactFiberHostConfig';
import {getChildHostContext, getRootHostContext} from './ReactFiberHostConfig';
import {createCursor, push, pop} from './ReactFiberStack.new';

declare class NoContextT {}
const NO_CONTEXT: NoContextT = ({}: any);

const contextStackCursor: StackCursor<HostContext | NoContextT> = createCursor(
NO_CONTEXT,
);
const contextFiberStackCursor: StackCursor<Fiber | NoContextT> = createCursor(
NO_CONTEXT,
const contextStackCursor: StackCursor<HostContext | null> = createCursor(null);
const contextFiberStackCursor: StackCursor<Fiber | null> = createCursor(null);
const rootInstanceStackCursor: StackCursor<Container | null> = createCursor(
null,
);
const rootInstanceStackCursor: StackCursor<
Container | NoContextT,
> = createCursor(NO_CONTEXT);

function requiredContext<Value>(c: Value | NoContextT): Value {
if (c === NO_CONTEXT) {
throw new Error(
'Expected host context to exist. This error is likely caused by a bug ' +
'in React. Please file an issue.',
);
}

function requiredContext<Value>(c: Value | null): Value {
if (__DEV__) {
if (c === null) {
console.error(
'Expected host context to exist. This error is likely caused by a bug ' +
'in React. Please file an issue.',
);
}
}
return (c: any);
}

function getCurrentRootHostContainer(): null | Container {
const container = rootInstanceStackCursor.current;
return container === NO_CONTEXT ? null : ((container: any): Container);
return rootInstanceStackCursor.current;
}

function getRootHostContainer(): Container {
Expand All @@ -61,7 +54,7 @@ function pushHostContainer(fiber: Fiber, nextRootInstance: Container) {
// we'd have a different number of entries on the stack depending on
// whether getRootHostContext() throws somewhere in renderer code or not.
// So we push an empty value first. This lets us safely unwind on errors.
push(contextStackCursor, NO_CONTEXT, fiber);
push(contextStackCursor, null, fiber);
const nextRootContext = getRootHostContext(nextRootInstance);
// Now that we know this function doesn't throw, replace it.
pop(contextStackCursor, fiber);
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37 changes: 15 additions & 22 deletions packages/react-reconciler/src/ReactFiberHostContext.old.js
Original file line number Diff line number Diff line change
Expand Up @@ -14,33 +14,26 @@ import type {Container, HostContext} from './ReactFiberHostConfig';
import {getChildHostContext, getRootHostContext} from './ReactFiberHostConfig';
import {createCursor, push, pop} from './ReactFiberStack.old';

declare class NoContextT {}
const NO_CONTEXT: NoContextT = ({}: any);

const contextStackCursor: StackCursor<HostContext | NoContextT> = createCursor(
NO_CONTEXT,
);
const contextFiberStackCursor: StackCursor<Fiber | NoContextT> = createCursor(
NO_CONTEXT,
const contextStackCursor: StackCursor<HostContext | null> = createCursor(null);
const contextFiberStackCursor: StackCursor<Fiber | null> = createCursor(null);
const rootInstanceStackCursor: StackCursor<Container | null> = createCursor(
null,
);
const rootInstanceStackCursor: StackCursor<
Container | NoContextT,
> = createCursor(NO_CONTEXT);

function requiredContext<Value>(c: Value | NoContextT): Value {
if (c === NO_CONTEXT) {
throw new Error(
'Expected host context to exist. This error is likely caused by a bug ' +
'in React. Please file an issue.',
);
}

function requiredContext<Value>(c: Value | null): Value {
if (__DEV__) {
if (c === null) {
console.error(
'Expected host context to exist. This error is likely caused by a bug ' +
'in React. Please file an issue.',
);
}
}
return (c: any);
}

function getCurrentRootHostContainer(): null | Container {
const container = rootInstanceStackCursor.current;
return container === NO_CONTEXT ? null : ((container: any): Container);
return rootInstanceStackCursor.current;
}

function getRootHostContainer(): Container {
Expand All @@ -61,7 +54,7 @@ function pushHostContainer(fiber: Fiber, nextRootInstance: Container) {
// we'd have a different number of entries on the stack depending on
// whether getRootHostContext() throws somewhere in renderer code or not.
// So we push an empty value first. This lets us safely unwind on errors.
push(contextStackCursor, NO_CONTEXT, fiber);
push(contextStackCursor, null, fiber);
const nextRootContext = getRootHostContext(nextRootInstance);
// Now that we know this function doesn't throw, replace it.
pop(contextStackCursor, fiber);
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Original file line number Diff line number Diff line change
Expand Up @@ -30,72 +30,10 @@ describe('ReactFiberHostContext', () => {

global.IS_REACT_ACT_ENVIRONMENT = true;

// @gate __DEV__
it('works with null host context', async () => {
let creates = 0;
const Renderer = ReactFiberReconciler({
prepareForCommit: function() {
return null;
},
resetAfterCommit: function() {},
getRootHostContext: function() {
return null;
},
getChildHostContext: function() {
return null;
},
shouldSetTextContent: function() {
return false;
},
createInstance: function() {
creates++;
},
finalizeInitialChildren: function() {
return null;
},
appendInitialChild: function() {
return null;
},
now: function() {
return 0;
},
appendChildToContainer: function() {
return null;
},
clearContainer: function() {},
getCurrentEventPriority: function() {
return DefaultEventPriority;
},
prepareRendererToRender: function() {},
resetRendererAfterRender: function() {},
supportsMutation: true,
requestPostPaintCallback: function() {},
});

const container = Renderer.createContainer(
/* root: */ null,
ConcurrentRoot,
null,
false,
'',
null,
);
act(() => {
Renderer.updateContainer(
<a>
<b />
</a>,
container,
/* parentComponent: */ null,
/* callback: */ null,
);
});
expect(creates).toBe(2);
});

// @gate __DEV__
it('should send the context to prepareForCommit and resetAfterCommit', () => {
const rootContext = {};
const childContext = {};
const Renderer = ReactFiberReconciler({
prepareForCommit: function(hostContext) {
expect(hostContext).toBe(rootContext);
Expand All @@ -105,10 +43,10 @@ describe('ReactFiberHostContext', () => {
expect(hostContext).toBe(rootContext);
},
getRootHostContext: function() {
return null;
return rootContext;
},
getChildHostContext: function() {
return null;
return childContext;
},
shouldSetTextContent: function() {
return false;
Expand Down

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