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[Fizz] Preload "suspensey" images #27191

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Merged
gnoff merged 1 commit into from
Aug 10, 2023
Merged

[Fizz] Preload "suspensey" images #27191

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111 changes: 93 additions & 18 deletions packages/react-dom-bindings/src/server/ReactFizzConfigDOM.js
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2370,6 +2370,78 @@ function pushStyleContents(
return;
}

function getImagePreloadKey(
href: string,
imageSrcSet: ?string,
imageSizes: ?string,
) {
let uniquePart = '';
if (typeof imageSrcSet === 'string' && imageSrcSet !== '') {
uniquePart += '[' + imageSrcSet + ']';
if (typeof imageSizes === 'string') {
uniquePart += '[' + imageSizes + ']';
}
} else {
uniquePart += '[][]' + href;
}
return getResourceKey('image', uniquePart);
}

function pushImg(
target: Array<Chunk | PrecomputedChunk>,
props: Object,
resources: Resources,
): null {
if (
props.loading !== 'lazy' &&
typeof props.src === 'string' &&
props.fetchPriority !== 'low'
) {
// We have a suspensey image and ought to preload it to optimize the loading of display blocking
// resources.
const {src, imageSrcSet, imageSizes} = props;
const key = getImagePreloadKey(src, imageSrcSet, imageSizes);
let resource = resources.preloadsMap.get(key);
if (!resource) {
resource = {
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Collaborator

@sebmarkbage sebmarkbage Aug 10, 2023

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Let's extract this stuff too like getPreloadResource(...).

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Collaborator Author

@gnoff gnoff Aug 10, 2023

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I'd like to but I think it needs to go in another PR. there are challenges with this b/c the current implementation is highly optimized to avoid creating props object unless absolutely required and so this can't be tidily implemented in a single function. Also I should do the same thing for stylesheet and other resource types

type: 'preload',
chunks: [],
state: NoState,
props: {
rel: 'preload',
as: 'image',
// There is a bug in Safari where imageSrcSet is not respected on preload links
// so we omit the href here if we have imageSrcSet b/c safari will load the wrong image.
// This harms older browers that do not support imageSrcSet by making their preloads not work
// but this population is shrinking fast and is already small so we accept this tradeoff.
href: imageSrcSet ? undefined : src,
imageSrcSet,
imageSizes,
crossOrigin: props.crossOrigin,
integrity: props.integrity,
type: props.type,
fetchPriority: props.fetchPriority,
referrerPolicy: props.referrerPolicy,
},
};
resources.preloadsMap.set(key, resource);
if (__DEV__) {
markAsRenderedResourceDEV(resource, props);
}
pushLinkImpl(resource.chunks, resource.props);
}
if (
props.fetchPriority === 'high' ||
resources.highImagePreloads.size < 10
) {
resources.highImagePreloads.add(resource);
} else {
resources.bulkPreloads.add(resource);
}
}
return pushSelfClosing(target, props, 'img');
}

function pushSelfClosing(
target: Array<Chunk | PrecomputedChunk>,
props: Object,
Expand Down Expand Up @@ -3172,14 +3244,16 @@ export function pushStartInstance(
case 'pre': {
return pushStartPreformattedElement(target, props, type);
}
case 'img': {
return pushImg(target, props, resources);
}
// Omitted close tags
case 'base':
case 'area':
case 'br':
case 'col':
case 'embed':
case 'hr':
case 'img':
case 'keygen':
case 'param':
case 'source':
Expand Down Expand Up @@ -4242,6 +4316,9 @@ export function writePreamble(
resources.fontPreloads.forEach(flushResourceInPreamble, destination);
resources.fontPreloads.clear();

resources.highImagePreloads.forEach(flushResourceInPreamble, destination);
resources.highImagePreloads.clear();

// Flush unblocked stylesheets by precedence
resources.precedences.forEach(flushAllStylesInPreamble, destination);

Expand All @@ -4250,8 +4327,8 @@ export function writePreamble(
resources.scripts.forEach(flushResourceInPreamble, destination);
resources.scripts.clear();

resources.explicitPreloads.forEach(flushResourceInPreamble, destination);
resources.explicitPreloads.clear();
resources.bulkPreloads.forEach(flushResourceInPreamble, destination);
resources.bulkPreloads.clear();

// Write embedding preloadChunks
const preloadChunks = responseState.preloadChunks;
Expand Down Expand Up @@ -4308,6 +4385,9 @@ export function writeHoistables(
resources.fontPreloads.forEach(flushResourceLate, destination);
resources.fontPreloads.clear();

resources.highImagePreloads.forEach(flushResourceInPreamble, destination);
resources.highImagePreloads.clear();

// Preload any stylesheets. these will emit in a render instruction that follows this
// but we want to kick off preloading as soon as possible
resources.precedences.forEach(preloadLateStyles, destination);
Expand All @@ -4318,8 +4398,8 @@ export function writeHoistables(
resources.scripts.forEach(flushResourceLate, destination);
resources.scripts.clear();

resources.explicitPreloads.forEach(flushResourceLate, destination);
resources.explicitPreloads.clear();
resources.bulkPreloads.forEach(flushResourceLate, destination);
resources.bulkPreloads.clear();

// Write embedding preloadChunks
const preloadChunks = responseState.preloadChunks;
Expand Down Expand Up @@ -4859,12 +4939,13 @@ export type Resources = {
// Flushing queues for Resource dependencies
preconnects: Set<PreconnectResource>,
fontPreloads: Set<PreloadResource>,
highImagePreloads: Set<PreloadResource>,
// usedImagePreloads: Set<PreloadResource>,
precedences: Map<string, Set<StyleResource>>,
stylePrecedences: Map<string, StyleTagResource>,
bootstrapScripts: Set<PreloadResource>,
scripts: Set<ScriptResource>,
explicitPreloads: Set<PreloadResource>,
bulkPreloads: Set<PreloadResource>,

// Module-global-like reference for current boundary resources
boundaryResources: ?BoundaryResources,
Expand All @@ -4883,12 +4964,13 @@ export function createResources(): Resources {
// cleared on flush
preconnects: new Set(),
fontPreloads: new Set(),
highImagePreloads: new Set(),
// usedImagePreloads: new Set(),
precedences: new Map(),
stylePrecedences: new Map(),
bootstrapScripts: new Set(),
scripts: new Set(),
explicitPreloads: new Set(),
bulkPreloads: new Set(),

// like a module global for currently rendering boundary
boundaryResources: null,
Expand Down Expand Up @@ -5086,16 +5168,7 @@ export function preload(href: string, options: PreloadOptions) {
// both. This is to prevent identical calls with the same srcSet and sizes to be duplicated
// by varying the href. this is an edge case but it is the most correct behavior.
const {imageSrcSet, imageSizes} = options;
let uniquePart = '';
if (typeof imageSrcSet === 'string' && imageSrcSet !== '') {
uniquePart += '[' + imageSrcSet + ']';
if (typeof imageSizes === 'string') {
uniquePart += '[' + imageSizes + ']';
}
} else {
uniquePart += '[][]' + href;
}
key = getResourceKey(as, uniquePart);
key = getImagePreloadKey(href, imageSrcSet, imageSizes);
} else {
key = getResourceKey(as, href);
}
Expand Down Expand Up @@ -5177,8 +5250,10 @@ export function preload(href: string, options: PreloadOptions) {
}
if (as === 'font') {
resources.fontPreloads.add(resource);
} else if (as === 'image' && options.fetchPriority === 'high') {
resources.highImagePreloads.add(resource);
} else {
resources.explicitPreloads.add(resource);
resources.bulkPreloads.add(resource);
}
flushResources(request);
}
Expand Down
157 changes: 157 additions & 0 deletions packages/react-dom/src/__tests__/ReactDOMFloat-test.js
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3771,6 +3771,163 @@ body {
);
});

it('can emit preloads for non-lazy images that are rendered', async () => {
function App() {
ReactDOM.preload('script', {as: 'script'});
ReactDOM.preload('a', {as: 'image'});
ReactDOM.preload('b', {as: 'image'});
return (
<html>
<body>
<img src="a" />
<img src="b" loading="lazy" />
<img src="b2" loading="lazy" />
<img src="c" imageSrcSet="srcsetc" />
<img src="d" imageSrcSet="srcsetd" imageSizes="sizesd" />
<img src="d" imageSrcSet="srcsetd" imageSizes="sizesd2" />
</body>
</html>
);
}

await act(() => {
renderToPipeableStream(<App />).pipe(writable);
});

// non-lazy images are first, then arbitrary preloads like for the script and lazy images
expect(getMeaningfulChildren(document)).toEqual(
<html>
<head>
<link rel="preload" href="a" as="image" />
<link rel="preload" as="image" imagesrcset="srcsetc" />
<link
rel="preload"
as="image"
imagesrcset="srcsetd"
imagesizes="sizesd"
/>
<link
rel="preload"
as="image"
imagesrcset="srcsetd"
imagesizes="sizesd2"
/>
<link rel="preload" href="script" as="script" />
<link rel="preload" href="b" as="image" />
</head>
<body>
<img src="a" />
<img src="b" loading="lazy" />
<img src="b2" loading="lazy" />
<img src="c" imagesrcset="srcsetc" />
<img src="d" imagesrcset="srcsetd" imagesizes="sizesd" />
<img src="d" imagesrcset="srcsetd" imagesizes="sizesd2" />
</body>
</html>,
);
});

it('Does not preload lazy images', async () => {
function App() {
ReactDOM.preload('a', {as: 'image'});
return (
<html>
<body>
<img src="a" fetchPriority="low" />
<img src="b" fetchPriority="low" />
</body>
</html>
);
}
await act(() => {
renderToPipeableStream(<App />).pipe(writable);
});

expect(getMeaningfulChildren(document)).toEqual(
<html>
<head>
<link rel="preload" as="image" href="a" />
</head>
<body>
<img src="a" fetchpriority="low" />
<img src="b" fetchpriority="low" />
</body>
</html>,
);
});

it('preloads up to 10 suspensey images as high priority when fetchPriority is not specified', async () => {
function App() {
ReactDOM.preload('1', {as: 'image', fetchPriority: 'high'});
ReactDOM.preload('auto', {as: 'image'});
ReactDOM.preload('low', {as: 'image', fetchPriority: 'low'});
ReactDOM.preload('9', {as: 'image', fetchPriority: 'high'});
ReactDOM.preload('10', {as: 'image', fetchPriority: 'high'});
return (
<html>
<body>
{/* skipping 1 */}
<img src="2" />
<img src="3" fetchPriority="auto" />
<img src="4" fetchPriority="high" />
<img src="5" />
<img src="5low" fetchPriority="low" />
<img src="6" />
<img src="7" />
<img src="8" />
<img src="9" />
{/* skipping 10 */}
<img src="11" />
<img src="12" fetchPriority="high" />
</body>
</html>
);
}
await act(() => {
renderToPipeableStream(<App />).pipe(writable);
});

expect(getMeaningfulChildren(document)).toEqual(
<html>
<head>
{/* First we see the preloads calls that made it to the high priority image queue */}
<link rel="preload" as="image" href="1" fetchpriority="high" />
<link rel="preload" as="image" href="9" fetchpriority="high" />
<link rel="preload" as="image" href="10" fetchpriority="high" />
{/* Next we see up to 7 more images qualify for high priority image queue */}
<link rel="preload" as="image" href="2" />
<link rel="preload" as="image" href="3" fetchpriority="auto" />
<link rel="preload" as="image" href="4" fetchpriority="high" />
<link rel="preload" as="image" href="5" />
<link rel="preload" as="image" href="6" />
<link rel="preload" as="image" href="7" />
<link rel="preload" as="image" href="8" />
{/* Next we see images that are explicitly high priority and thus make it to the high priority image queue */}
<link rel="preload" as="image" href="12" fetchpriority="high" />
{/* Next we see the remaining preloads that did not make it to the high priority image queue */}
<link rel="preload" as="image" href="auto" />
<link rel="preload" as="image" href="low" fetchpriority="low" />
<link rel="preload" as="image" href="11" />
</head>
<body>
{/* skipping 1 */}
<img src="2" />
<img src="3" fetchpriority="auto" />
<img src="4" fetchpriority="high" />
<img src="5" />
<img src="5low" fetchpriority="low" />
<img src="6" />
<img src="7" />
<img src="8" />
<img src="9" />
{/* skipping 10 */}
<img src="11" />
<img src="12" fetchpriority="high" />
</body>
</html>,
);
});

describe('ReactDOM.prefetchDNS(href)', () => {
it('creates a dns-prefetch resource when called', async () => {
function App({url}) {
Expand Down