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experimental_use(context) #25202

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Sep 7, 2022
Merged

experimental_use(context) #25202

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113 changes: 58 additions & 55 deletions packages/react-reconciler/src/ReactFiberHooks.new.js
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@ import {
enableUseHook,
enableUseMemoCacheHook,
} from 'shared/ReactFeatureFlags';
import {REACT_CONTEXT_TYPE} from 'shared/ReactSymbols';

import {NoMode, ConcurrentMode, DebugTracingMode} from './ReactTypeOfMode';
import {
Expand Down Expand Up @@ -714,68 +715,70 @@ function createFunctionComponentUpdateQueue(): FunctionComponentUpdateQueue {
}

function use<T>(usable: Usable<T>): T {
if (
usable !== null &&
typeof usable === 'object' &&
typeof usable.then === 'function'
) {
// This is a thenable.
const thenable: Thenable<T> = (usable: any);

// Track the position of the thenable within this fiber.
const index = thenableIndexCounter;
thenableIndexCounter += 1;

switch (thenable.status) {
case 'fulfilled': {
const fulfilledValue: T = thenable.value;
return fulfilledValue;
}
case 'rejected': {
const rejectedError = thenable.reason;
throw rejectedError;
}
default: {
const prevThenableAtIndex: Thenable<T> | null = getPreviouslyUsedThenableAtIndex(
index,
);
if (prevThenableAtIndex !== null) {
switch (prevThenableAtIndex.status) {
case 'fulfilled': {
const fulfilledValue: T = prevThenableAtIndex.value;
return fulfilledValue;
}
case 'rejected': {
const rejectedError: mixed = prevThenableAtIndex.reason;
throw rejectedError;
}
default: {
// The thenable still hasn't resolved. Suspend with the same
// thenable as last time to avoid redundant listeners.
throw prevThenableAtIndex;
if (usable !== null && typeof usable === 'object') {
if (typeof usable.then === 'function') {
// This is a thenable.
const thenable: Thenable<T> = (usable: any);

// Track the position of the thenable within this fiber.
const index = thenableIndexCounter;
thenableIndexCounter += 1;

switch (thenable.status) {
case 'fulfilled': {
const fulfilledValue: T = thenable.value;
return fulfilledValue;
}
case 'rejected': {
const rejectedError = thenable.reason;
throw rejectedError;
}
default: {
const prevThenableAtIndex: Thenable<T> | null = getPreviouslyUsedThenableAtIndex(
index,
);
if (prevThenableAtIndex !== null) {
switch (prevThenableAtIndex.status) {
case 'fulfilled': {
const fulfilledValue: T = prevThenableAtIndex.value;
return fulfilledValue;
}
case 'rejected': {
const rejectedError: mixed = prevThenableAtIndex.reason;
throw rejectedError;
}
default: {
// The thenable still hasn't resolved. Suspend with the same
// thenable as last time to avoid redundant listeners.
throw prevThenableAtIndex;
}
}
} else {
// This is the first time something has been used at this index.
// Stash the thenable at the current index so we can reuse it during
// the next attempt.
trackUsedThenable(thenable, index);

// Suspend.
// TODO: Throwing here is an implementation detail that allows us to
// unwind the call stack. But we shouldn't allow it to leak into
// userspace. Throw an opaque placeholder value instead of the
// actual thenable. If it doesn't get captured by the work loop, log
// a warning, because that means something in userspace must have
// caught it.
throw thenable;
}
} else {
// This is the first time something has been used at this index.
// Stash the thenable at the current index so we can reuse it during
// the next attempt.
trackUsedThenable(thenable, index);

// Suspend.
// TODO: Throwing here is an implementation detail that allows us to
// unwind the call stack. But we shouldn't allow it to leak into
// userspace. Throw an opaque placeholder value instead of the
// actual thenable. If it doesn't get captured by the work loop, log
// a warning, because that means something in userspace must have
// caught it.
throw thenable;
}
}
} else if (
usable.$$typeof != null &&
usable.$$typeof === REACT_CONTEXT_TYPE
) {
const context: ReactContext<T> = (usable: any);
return readContext(context);
}
}

// TODO: Add support for Context

// eslint-disable-next-line react-internal/safe-string-coercion
throw new Error('An unsupported type was passed to use(): ' + String(usable));
}
Expand Down
113 changes: 58 additions & 55 deletions packages/react-reconciler/src/ReactFiberHooks.old.js
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@ import {
enableUseHook,
enableUseMemoCacheHook,
} from 'shared/ReactFeatureFlags';
import {REACT_CONTEXT_TYPE} from 'shared/ReactSymbols';

import {NoMode, ConcurrentMode, DebugTracingMode} from './ReactTypeOfMode';
import {
Expand Down Expand Up @@ -714,68 +715,70 @@ function createFunctionComponentUpdateQueue(): FunctionComponentUpdateQueue {
}

function use<T>(usable: Usable<T>): T {
if (
usable !== null &&
typeof usable === 'object' &&
typeof usable.then === 'function'
) {
// This is a thenable.
const thenable: Thenable<T> = (usable: any);

// Track the position of the thenable within this fiber.
const index = thenableIndexCounter;
thenableIndexCounter += 1;

switch (thenable.status) {
case 'fulfilled': {
const fulfilledValue: T = thenable.value;
return fulfilledValue;
}
case 'rejected': {
const rejectedError = thenable.reason;
throw rejectedError;
}
default: {
const prevThenableAtIndex: Thenable<T> | null = getPreviouslyUsedThenableAtIndex(
index,
);
if (prevThenableAtIndex !== null) {
switch (prevThenableAtIndex.status) {
case 'fulfilled': {
const fulfilledValue: T = prevThenableAtIndex.value;
return fulfilledValue;
}
case 'rejected': {
const rejectedError: mixed = prevThenableAtIndex.reason;
throw rejectedError;
}
default: {
// The thenable still hasn't resolved. Suspend with the same
// thenable as last time to avoid redundant listeners.
throw prevThenableAtIndex;
if (usable !== null && typeof usable === 'object') {
if (typeof usable.then === 'function') {
// This is a thenable.
const thenable: Thenable<T> = (usable: any);

// Track the position of the thenable within this fiber.
const index = thenableIndexCounter;
thenableIndexCounter += 1;

switch (thenable.status) {
case 'fulfilled': {
const fulfilledValue: T = thenable.value;
return fulfilledValue;
}
case 'rejected': {
const rejectedError = thenable.reason;
throw rejectedError;
}
default: {
const prevThenableAtIndex: Thenable<T> | null = getPreviouslyUsedThenableAtIndex(
index,
);
if (prevThenableAtIndex !== null) {
switch (prevThenableAtIndex.status) {
case 'fulfilled': {
const fulfilledValue: T = prevThenableAtIndex.value;
return fulfilledValue;
}
case 'rejected': {
const rejectedError: mixed = prevThenableAtIndex.reason;
throw rejectedError;
}
default: {
// The thenable still hasn't resolved. Suspend with the same
// thenable as last time to avoid redundant listeners.
throw prevThenableAtIndex;
}
}
} else {
// This is the first time something has been used at this index.
// Stash the thenable at the current index so we can reuse it during
// the next attempt.
trackUsedThenable(thenable, index);

// Suspend.
// TODO: Throwing here is an implementation detail that allows us to
// unwind the call stack. But we shouldn't allow it to leak into
// userspace. Throw an opaque placeholder value instead of the
// actual thenable. If it doesn't get captured by the work loop, log
// a warning, because that means something in userspace must have
// caught it.
throw thenable;
}
} else {
// This is the first time something has been used at this index.
// Stash the thenable at the current index so we can reuse it during
// the next attempt.
trackUsedThenable(thenable, index);

// Suspend.
// TODO: Throwing here is an implementation detail that allows us to
// unwind the call stack. But we shouldn't allow it to leak into
// userspace. Throw an opaque placeholder value instead of the
// actual thenable. If it doesn't get captured by the work loop, log
// a warning, because that means something in userspace must have
// caught it.
throw thenable;
}
}
} else if (
usable.$$typeof != null &&
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nit: do you need a null check here? if it's null then the subsequent === check will fail anyway

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Ahh thanks for catching this, will fix in #25226!

usable.$$typeof === REACT_CONTEXT_TYPE
) {
const context: ReactContext<T> = (usable: any);
return readContext(context);
}
}

// TODO: Add support for Context

// eslint-disable-next-line react-internal/safe-string-coercion
throw new Error('An unsupported type was passed to use(): ' + String(usable));
}
Expand Down
24 changes: 24 additions & 0 deletions packages/react-reconciler/src/__tests__/ReactWakeable-test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -315,4 +315,28 @@ describe('ReactWakeable', () => {
]);
expect(root).toMatchRenderedOutput('Caught an error: Oops!');
});

// @gate enableUseHook
test('basic use(context)', () => {
const ContextA = React.createContext('');
const ContextB = React.createContext('B');

function Sync() {
const text = use(ContextA) + use(ContextB);
return text;
}

function App() {
return (
<ContextA.Provider value="A">
<Sync />
</ContextA.Provider>
);
}

const root = ReactNoop.createRoot();
root.render(<App />);
expect(Scheduler).toFlushWithoutYielding();
expect(root).toMatchRenderedOutput('AB');
});
});
2 changes: 1 addition & 1 deletion packages/shared/ReactTypes.js
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Original file line number Diff line number Diff line change
Expand Up @@ -214,4 +214,4 @@ export type StartTransitionOptions = {
};

// TODO: Add Context support
export type Usable<T> = Thenable<T>;
export type Usable<T> = Thenable<T> | ReactContext<T>;