router.prefetch should not trigger a React update

[acdlite]

The prefetch reducer doesn't actually modify any React state. It just writes to a mutable cache. So we shouldn't bother calling setState/dispatch; we can just re-run the reducer directly using the current state.

[ijjk]

Tests Passed

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	acdlite/next.js remove-prefetch-dispatch	Change
buildDuration	18.6s	15.1s	N/A
buildDurationCached	14.2s	11.9s	N/A
nodeModulesSize	419 MB	419 MB	⚠️ +148 kB
nextStartRea..uration (ms)	419ms	418ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	acdlite/next.js remove-prefetch-dispatch	Change
5306-HASH.js gzip	54.1 kB	54.1 kB	N/A
8276.HASH.js gzip	169 B	168 B	N/A
8377-HASH.js gzip	5.46 kB	5.46 kB	N/A
bccd1874-HASH.js gzip	52.9 kB	52.9 kB	N/A
framework-HASH.js gzip	57.5 kB	57.5 kB	N/A
main-app-HASH.js gzip	239 B	241 B	N/A
main-HASH.js gzip	34.6 kB	34.6 kB	N/A
webpack-HASH.js gzip	1.71 kB	1.71 kB	N/A
Overall change	0 B	0 B	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	acdlite/next.js remove-prefetch-dispatch	Change
polyfills-HASH.js gzip	39.4 kB	39.4 kB	✓
Overall change	39.4 kB	39.4 kB	✓

Client Pages

	vercel/next.js canary	acdlite/next.js remove-prefetch-dispatch	Change
_app-HASH.js gzip	193 B	193 B	✓
_error-HASH.js gzip	193 B	193 B	✓
amp-HASH.js gzip	512 B	510 B	N/A
css-HASH.js gzip	343 B	342 B	N/A
dynamic-HASH.js gzip	1.84 kB	1.84 kB	✓
edge-ssr-HASH.js gzip	265 B	265 B	✓
head-HASH.js gzip	363 B	362 B	N/A
hooks-HASH.js gzip	393 B	392 B	N/A
image-HASH.js gzip	4.59 kB	4.58 kB	N/A
index-HASH.js gzip	268 B	268 B	✓
link-HASH.js gzip	2.35 kB	2.35 kB	N/A
routerDirect..HASH.js gzip	328 B	328 B	✓
script-HASH.js gzip	397 B	397 B	✓
withRouter-HASH.js gzip	323 B	326 B	N/A
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	3.59 kB	3.59 kB	✓

Client Build Manifests

	vercel/next.js canary	acdlite/next.js remove-prefetch-dispatch	Change
_buildManifest.js gzip	748 B	747 B	N/A
Overall change	0 B	0 B	✓

Rendered Page Sizes

	vercel/next.js canary	acdlite/next.js remove-prefetch-dispatch	Change
index.html gzip	523 B	522 B	N/A
link.html gzip	538 B	536 B	N/A
withRouter.html gzip	519 B	519 B	✓
Overall change	519 B	519 B	✓

Edge SSR bundle Size Overall increase ⚠️

	vercel/next.js canary	acdlite/next.js remove-prefetch-dispatch	Change
edge-ssr.js gzip	129 kB	129 kB	N/A
page.js gzip	209 kB	210 kB	⚠️ +684 B
Overall change	209 kB	210 kB	⚠️ +684 B

Middleware size

	vercel/next.js canary	acdlite/next.js remove-prefetch-dispatch	Change
middleware-b..fest.js gzip	669 B	667 B	N/A
middleware-r..fest.js gzip	155 B	156 B	N/A
middleware.js gzip	31.3 kB	31.3 kB	N/A
edge-runtime..pack.js gzip	844 B	844 B	✓
Overall change	844 B	844 B	✓

Next Runtimes Overall increase ⚠️

	vercel/next.js canary	acdlite/next.js remove-prefetch-dispatch	Change
274-experime...dev.js gzip	322 B	322 B	✓
274.runtime.dev.js gzip	314 B	314 B	✓
app-page-exp...dev.js gzip	376 kB	378 kB	⚠️ +1.45 kB
app-page-exp..prod.js gzip	131 kB	132 kB	⚠️ +1.03 kB
app-page-tur..prod.js gzip	144 kB	145 kB	⚠️ +1.03 kB
app-page-tur..prod.js gzip	140 kB	141 kB	⚠️ +1.03 kB
app-page.run...dev.js gzip	364 kB	365 kB	⚠️ +1.48 kB
app-page.run..prod.js gzip	127 kB	128 kB	⚠️ +1.03 kB
app-route-ex...dev.js gzip	37.6 kB	37.6 kB	✓
app-route-ex..prod.js gzip	25.6 kB	25.6 kB	✓
app-route-tu..prod.js gzip	25.6 kB	25.6 kB	✓
app-route-tu..prod.js gzip	25.4 kB	25.4 kB	✓
app-route.ru...dev.js gzip	39.2 kB	39.2 kB	✓
app-route.ru..prod.js gzip	25.4 kB	25.4 kB	✓
pages-api-tu..prod.js gzip	9.69 kB	9.69 kB	✓
pages-api.ru...dev.js gzip	11.6 kB	11.6 kB	✓
pages-api.ru..prod.js gzip	9.68 kB	9.68 kB	✓
pages-turbo...prod.js gzip	21.9 kB	21.9 kB	✓
pages.runtim...dev.js gzip	27.7 kB	27.7 kB	✓
pages.runtim..prod.js gzip	21.9 kB	21.9 kB	✓
server.runti..prod.js gzip	916 kB	916 kB	✓
Overall change	2.48 MB	2.49 MB	⚠️ +7.05 kB

build cache

	vercel/next.js canary	acdlite/next.js remove-prefetch-dispatch	Change
0.pack gzip	2.11 MB	2.1 MB	N/A
index.pack gzip	75.3 kB	74.9 kB	N/A
Overall change	0 B	0 B	✓

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Commit: 399c1de