Pages router: Use attribute-based head children reconciler when strictNextHead is enabled
#65408
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eps1lon
changed the title
strictNextHead is enabled
Tests Passed |
Stats from current PRDefault Build (Increase detected
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| vercel/next.js canary | vercel/next.js sebbie/pages-router-head-csr-reconciler | Change | |
|---|---|---|---|
| buildDuration | 55.5s | 23.5s | N/A |
| buildDurationCached | 12.6s | 11.4s | N/A |
| nodeModulesSize | 360 MB | 360 MB | N/A |
| nextStartRea..uration (ms) | 724ms | 534ms | N/A |
Client Bundles (main, webpack)
| vercel/next.js canary | vercel/next.js sebbie/pages-router-head-csr-reconciler | Change | |
|---|---|---|---|
| 1103-HASH.js gzip | 31.9 kB | 31.9 kB | N/A |
| 1a9f679d-HASH.js gzip | 53.5 kB | 53.5 kB | N/A |
| 335-HASH.js gzip | 5.05 kB | 5.05 kB | ✓ |
| 7953.HASH.js gzip | 169 B | 169 B | ✓ |
| framework-HASH.js gzip | 45.2 kB | 45.2 kB | ✓ |
| main-app-HASH.js gzip | 231 B | 228 B | N/A |
| main-HASH.js gzip | 31.6 kB | 31.6 kB | N/A |
| webpack-HASH.js gzip | 1.65 kB | 1.65 kB | N/A |
| Overall change | 50.4 kB | 50.4 kB | ✓ |
Legacy Client Bundles (polyfills)
| vercel/next.js canary | vercel/next.js sebbie/pages-router-head-csr-reconciler | Change | |
|---|---|---|---|
| polyfills-HASH.js gzip | 31 kB | 31 kB | ✓ |
| Overall change | 31 kB | 31 kB | ✓ |
Client Pages
| vercel/next.js canary | vercel/next.js sebbie/pages-router-head-csr-reconciler | Change | |
|---|---|---|---|
| _app-HASH.js gzip | 192 B | 193 B | N/A |
| _error-HASH.js gzip | 192 B | 193 B | N/A |
| amp-HASH.js gzip | 507 B | 511 B | N/A |
| css-HASH.js gzip | 341 B | 343 B | N/A |
| dynamic-HASH.js gzip | 2.52 kB | 2.52 kB | ✓ |
| edge-ssr-HASH.js gzip | 266 B | 265 B | N/A |
| head-HASH.js gzip | 362 B | 365 B | N/A |
| hooks-HASH.js gzip | 392 B | 392 B | ✓ |
| image-HASH.js gzip | 4.27 kB | 4.27 kB | ✓ |
| index-HASH.js gzip | 268 B | 268 B | ✓ |
| link-HASH.js gzip | 2.69 kB | 2.7 kB | N/A |
| routerDirect..HASH.js gzip | 329 B | 328 B | N/A |
| script-HASH.js gzip | 397 B | 397 B | ✓ |
| withRouter-HASH.js gzip | 324 B | 324 B | ✓ |
| 1afbb74e6ecf..834.css gzip | 106 B | 106 B | ✓ |
| Overall change | 8.27 kB | 8.27 kB | ✓ |
Client Build Manifests
| vercel/next.js canary | vercel/next.js sebbie/pages-router-head-csr-reconciler | Change | |
|---|---|---|---|
| _buildManifest.js gzip | 483 B | 484 B | N/A |
| Overall change | 0 B | 0 B | ✓ |
Rendered Page Sizes
| vercel/next.js canary | vercel/next.js sebbie/pages-router-head-csr-reconciler | Change | |
|---|---|---|---|
| index.html gzip | 527 B | 527 B | ✓ |
| link.html gzip | 540 B | 539 B | N/A |
| withRouter.html gzip | 523 B | 523 B | ✓ |
| Overall change | 1.05 kB | 1.05 kB | ✓ |
Edge SSR bundle Size
| vercel/next.js canary | vercel/next.js sebbie/pages-router-head-csr-reconciler | Change | |
|---|---|---|---|
| edge-ssr.js gzip | 94.8 kB | 94.7 kB | N/A |
| page.js gzip | 182 kB | 182 kB | N/A |
| Overall change | 0 B | 0 B | ✓ |
Middleware size
| vercel/next.js canary | vercel/next.js sebbie/pages-router-head-csr-reconciler | Change | |
|---|---|---|---|
| middleware-b..fest.js gzip | 623 B | 624 B | N/A |
| middleware-r..fest.js gzip | 156 B | 156 B | ✓ |
| middleware.js gzip | 25.7 kB | 25.7 kB | N/A |
| edge-runtime..pack.js gzip | 839 B | 839 B | ✓ |
| Overall change | 995 B | 995 B | ✓ |
Next Runtimes
| vercel/next.js canary | vercel/next.js sebbie/pages-router-head-csr-reconciler | Change | |
|---|---|---|---|
| app-page-exp...dev.js gzip | 171 kB | 171 kB | ✓ |
| app-page-exp..prod.js gzip | 98.8 kB | 98.8 kB | ✓ |
| app-page-tur..prod.js gzip | 100 kB | 100 kB | ✓ |
| app-page-tur..prod.js gzip | 94.6 kB | 94.6 kB | ✓ |
| app-page.run...dev.js gzip | 157 kB | 157 kB | ✓ |
| app-page.run..prod.js gzip | 93.3 kB | 93.3 kB | ✓ |
| app-route-ex...dev.js gzip | 21.5 kB | 21.5 kB | ✓ |
| app-route-ex..prod.js gzip | 15.3 kB | 15.3 kB | ✓ |
| app-route-tu..prod.js gzip | 15.3 kB | 15.3 kB | ✓ |
| app-route-tu..prod.js gzip | 15 kB | 15 kB | ✓ |
| app-route.ru...dev.js gzip | 21.3 kB | 21.3 kB | ✓ |
| app-route.ru..prod.js gzip | 15 kB | 15 kB | ✓ |
| pages-api-tu..prod.js gzip | 9.55 kB | 9.55 kB | ✓ |
| pages-api.ru...dev.js gzip | 9.82 kB | 9.82 kB | ✓ |
| pages-api.ru..prod.js gzip | 9.55 kB | 9.55 kB | ✓ |
| pages-turbo...prod.js gzip | 21.5 kB | 21.5 kB | ✓ |
| pages.runtim...dev.js gzip | 22.1 kB | 22.1 kB | ✓ |
| pages.runtim..prod.js gzip | 21.5 kB | 21.5 kB | ✓ |
| server.runti..prod.js gzip | 51.7 kB | 51.7 kB | ✓ |
| Overall change | 964 kB | 964 kB | ✓ |
build cache Overall increase ⚠️
| vercel/next.js canary | vercel/next.js sebbie/pages-router-head-csr-reconciler | Change | |
|---|---|---|---|
| 0.pack gzip | 1.62 MB | 1.62 MB | N/A |
| index.pack gzip | 113 kB | 114 kB | |
| Overall change | 113 kB | 114 kB |
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In React 19, tags within `<head>` may be reordered to improve performance e.g. the viewport is floated earlier into the head. This breaks the current mechanism of `<Head>` managing its children. Every child of `Head` used to be prefixed with another `<meta>` tag that indicated that the next sibling would be managed by Next.js. Since React now reorders tags, that sibling relationship is broken. Client-side reconciliation by the `head-manager` during navigation would be broken resulting in orphaned and dupliated `<meta>` tags. We no longer prefix `<Head>` managed tags with a `<meta>` tag and instead mark them as owned via `data-next-head`. The old algorithm was also O(n*m) and ignored reordering so we can do the same thing here.
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eps1lon
requested review from
timneutkens,
ijjk,
shuding,
huozhi,
feedthejim,
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eps1lon
changed the title
strictNextHead is enabledstrictNextHead is enabled
gnoff
approved these changes
May 6, 2024
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Required for #65058
In React 19, tags within
<head>may be reordered to improve performance e.g. the viewport is floated earlier into the head.This breaks the current mechanism of
<Head>managing its children.Every child of
Headused to be prefixed with another<meta>tag that indicated that the next sibling would be managed by Next.js.Since React now reorders tags, that sibling relationship is broken. Client-side reconciliation by the
head-managerduring navigation would be broken resulting in orphaned and dupliated<meta>tags.We no longer prefix
<Head>managed tags with a<meta>tag and instead mark them as owned viadata-next-head.The old algorithm was also O(n*m) and ignored reordering so we can do the same thing here.
Closes NEXT-3326