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Fast JSX: Don't clone props object #28768

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Apr 5, 2024
Merged

Fast JSX: Don't clone props object #28768

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33 changes: 33 additions & 0 deletions packages/react/src/__tests__/ReactJSXRuntime-test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -374,4 +374,37 @@ describe('ReactJSXRuntime', () => {
}
expect(didCall).toBe(false);
});

// @gate enableRefAsProp
// @gate disableStringRefs
it('does not clone props object if key is not spread', async () => {
const config = {
foo: 'foo',
bar: 'bar',
};

const element = __DEV__
? JSXDEVRuntime.jsxDEV('div', config)
: JSXRuntime.jsx('div', config);
expect(element.props).toBe(config);

const configWithKey = {
foo: 'foo',
bar: 'bar',
// This only happens when the key is spread onto the element. A statically
// defined key is passed as a separate argument to the jsx() runtime.
key: 'key',
};

let elementWithSpreadKey;
expect(() => {
elementWithSpreadKey = __DEV__
? JSXDEVRuntime.jsxDEV('div', configWithKey)
: JSXRuntime.jsx('div', configWithKey);
}).toErrorDev(
'A props object containing a "key" prop is being spread into JSX',
{withoutStack: true},
);
expect(elementWithSpreadKey.props).not.toBe(configWithKey);
});
});
112 changes: 68 additions & 44 deletions packages/react/src/jsx/ReactJSXElement.js
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Original file line number Diff line number Diff line change
Expand Up @@ -314,11 +314,6 @@ function ReactElement(type, key, _ref, self, source, owner, props) {
* @param {string} key
*/
export function jsxProd(type, config, maybeKey) {
let propName;

// Reserved names are extracted
const props = {};

let key = null;
let ref = null;

Expand Down Expand Up @@ -351,22 +346,39 @@ export function jsxProd(type, config, maybeKey) {
}
}

// Remaining properties are added to a new props object
for (propName in config) {
if (
hasOwnProperty.call(config, propName) &&
// Skip over reserved prop names
propName !== 'key' &&
(enableRefAsProp || propName !== 'ref')
) {
if (enableRefAsProp && !disableStringRefs && propName === 'ref') {
props.ref = coerceStringRef(
config[propName],
ReactCurrentOwner.current,
type,
);
} else {
props[propName] = config[propName];
let props;
if (enableRefAsProp && disableStringRefs && !('key' in config)) {
// If key was not spread in, we can reuse the original props object. This
// only works for `jsx`, not `createElement`, because `jsx` is a compiler
// target and the compiler always passes a new object. For `createElement`,
// we can't assume a new object is passed every time because it can be
// called manually.
//
// Spreading key is a warning in dev. In a future release, we will not
// remove a spread key from the props object. (But we'll still warn.) We'll
// always pass the object straight through.
props = config;
} else {
// We need to remove reserved props (key, prop, ref). Create a fresh props
// object and copy over all the non-reserved props. We don't use `delete`
// because in V8 it will deopt the object to dictionary mode.
props = {};
for (const propName in config) {
if (
hasOwnProperty.call(config, propName) &&
// Skip over reserved prop names
propName !== 'key' &&
(enableRefAsProp || propName !== 'ref')
) {
if (enableRefAsProp && !disableStringRefs && propName === 'ref') {
props.ref = coerceStringRef(
config[propName],
ReactCurrentOwner.current,
type,
);
} else {
props[propName] = config[propName];
}
}
}
}
Expand All @@ -375,7 +387,7 @@ export function jsxProd(type, config, maybeKey) {
// Resolve default props
if (type && type.defaultProps) {
const defaultProps = type.defaultProps;
for (propName in defaultProps) {
for (const propName in defaultProps) {
if (props[propName] === undefined) {
props[propName] = defaultProps[propName];
}
Expand Down Expand Up @@ -538,11 +550,6 @@ export function jsxDEV(type, config, maybeKey, isStaticChildren, source, self) {
}
}

let propName;

// Reserved names are extracted
const props = {};

let key = null;
let ref = null;

Expand Down Expand Up @@ -578,22 +585,39 @@ export function jsxDEV(type, config, maybeKey, isStaticChildren, source, self) {
}
}

// Remaining properties are added to a new props object
for (propName in config) {
if (
hasOwnProperty.call(config, propName) &&
// Skip over reserved prop names
propName !== 'key' &&
(enableRefAsProp || propName !== 'ref')
) {
if (enableRefAsProp && !disableStringRefs && propName === 'ref') {
props.ref = coerceStringRef(
config[propName],
ReactCurrentOwner.current,
type,
);
} else {
props[propName] = config[propName];
let props;
if (enableRefAsProp && disableStringRefs && !('key' in config)) {
// If key was not spread in, we can reuse the original props object. This
// only works for `jsx`, not `createElement`, because `jsx` is a compiler
// target and the compiler always passes a new object. For `createElement`,
// we can't assume a new object is passed every time because it can be
// called manually.
//
// Spreading key is a warning in dev. In a future release, we will not
// remove a spread key from the props object. (But we'll still warn.) We'll
// always pass the object straight through.
props = config;
} else {
// We need to remove reserved props (key, prop, ref). Create a fresh props
// object and copy over all the non-reserved props. We don't use `delete`
// because in V8 it will deopt the object to dictionary mode.
props = {};
for (const propName in config) {
if (
hasOwnProperty.call(config, propName) &&
// Skip over reserved prop names
propName !== 'key' &&
(enableRefAsProp || propName !== 'ref')
) {
if (enableRefAsProp && !disableStringRefs && propName === 'ref') {
props.ref = coerceStringRef(
config[propName],
ReactCurrentOwner.current,
type,
);
} else {
props[propName] = config[propName];
}
}
}
}
Expand All @@ -602,7 +626,7 @@ export function jsxDEV(type, config, maybeKey, isStaticChildren, source, self) {
// Resolve default props
if (type && type.defaultProps) {
const defaultProps = type.defaultProps;
for (propName in defaultProps) {
for (const propName in defaultProps) {
if (props[propName] === undefined) {
props[propName] = defaultProps[propName];
}
Expand Down