Fix hmr updates with rebuilding for build errors

[huozhi]

What

• Sometimes the display of the error overlay is not consistent even when you fixed the error

Example:

• You have a client page, and you add metadata export, Next.js will error that it's not allowed in client component.
• You fix it, but the error overlay is not disappeared. Or you fix it, then introduce it again, then fix it again, the error overlay is still there.

How

We're checking if the HMR webpack hash is changed to decide if we're going to do a hot update in BUILT and SYNC event, but we update the hash at the very beginning of the event handler. isUpdateAvailable() will return false in the later calls but the hash has already changed before. So we check if they change before applying hot updates, and then use it later with isUpdateAvailable() to determine if necessary to process a new hot update

There's a early return in the warnings condition which lead to confusing can be optimized, we removed it and dropped the incorrect condition at the end where we apply the hot updates. We should just call handleHotUpdate() because that one already checks if there’s an update available.

Closes NEXT-2107

[ijjk]

Tests Passed

[ijjk]

Stats from current PR

Default Build

General

	vercel/next.js canary	vercel/next.js fix/hmr-build-error	Change
buildDuration	12.8s	13s	⚠️ +146ms
buildDurationCached	7.2s	6.3s	N/A
nodeModulesSize	200 MB	200 MB	N/A
nextStartRea..uration (ms)	425ms	426ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	vercel/next.js fix/hmr-build-error	Change
193.HASH.js gzip	181 B	182 B	N/A
3f784ff6-HASH.js gzip	53.4 kB	53.4 kB	✓
433-HASH.js gzip	28.9 kB	28.9 kB	N/A
framework-HASH.js gzip	45.2 kB	45.2 kB	✓
main-app-HASH.js gzip	239 B	242 B	N/A
main-HASH.js gzip	31.8 kB	31.8 kB	N/A
webpack-HASH.js gzip	1.7 kB	1.7 kB	N/A
Overall change	98.6 kB	98.6 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js fix/hmr-build-error	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js fix/hmr-build-error	Change
_app-HASH.js gzip	194 B	195 B	N/A
_error-HASH.js gzip	183 B	181 B	N/A
amp-HASH.js gzip	504 B	502 B	N/A
css-HASH.js gzip	321 B	321 B	✓
dynamic-HASH.js gzip	2.5 kB	2.5 kB	N/A
edge-ssr-HASH.js gzip	255 B	253 B	N/A
head-HASH.js gzip	350 B	349 B	N/A
hooks-HASH.js gzip	369 B	369 B	✓
image-HASH.js gzip	4.28 kB	4.28 kB	N/A
index-HASH.js gzip	255 B	256 B	N/A
link-HASH.js gzip	2.61 kB	2.61 kB	✓
routerDirect..HASH.js gzip	312 B	311 B	N/A
script-HASH.js gzip	385 B	383 B	N/A
withRouter-HASH.js gzip	307 B	308 B	N/A
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	3.4 kB	3.4 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js fix/hmr-build-error	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 fix/hmr-build-error	Change
index.html gzip	528 B	528 B	✓
link.html gzip	540 B	540 B	✓
withRouter.html gzip	522 B	524 B	N/A
Overall change	1.07 kB	1.07 kB	✓

Edge SSR bundle Size

	vercel/next.js canary	vercel/next.js fix/hmr-build-error	Change
edge-ssr.js gzip	93.9 kB	93.9 kB	N/A
page.js gzip	148 kB	148 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js canary	vercel/next.js fix/hmr-build-error	Change
middleware-b..fest.js gzip	621 B	625 B	N/A
middleware-r..fest.js gzip	151 B	151 B	✓
middleware.js gzip	37.5 kB	37.5 kB	N/A
edge-runtime..pack.js gzip	1.92 kB	1.92 kB	✓
Overall change	2.07 kB	2.07 kB	✓

Next Runtimes

	vercel/next.js canary	vercel/next.js fix/hmr-build-error	Change
app-page-exp...dev.js gzip	169 kB	169 kB	✓
app-page-exp..prod.js gzip	95.3 kB	95.3 kB	✓
app-page-tur..prod.js gzip	96 kB	96 kB	✓
app-page-tur..prod.js gzip	90.5 kB	90.5 kB	✓
app-page.run...dev.js gzip	142 kB	142 kB	✓
app-page.run..prod.js gzip	89.9 kB	89.9 kB	✓
app-route-ex...dev.js gzip	24.1 kB	24.1 kB	✓
app-route-ex..prod.js gzip	16.8 kB	16.8 kB	✓
app-route-tu..prod.js gzip	16.8 kB	16.8 kB	✓
app-route-tu..prod.js gzip	16.3 kB	16.3 kB	✓
app-route.ru...dev.js gzip	23.5 kB	23.5 kB	✓
app-route.ru..prod.js gzip	16.3 kB	16.3 kB	✓
pages-api-tu..prod.js gzip	9.38 kB	9.38 kB	✓
pages-api.ru...dev.js gzip	9.65 kB	9.65 kB	✓
pages-api.ru..prod.js gzip	9.37 kB	9.37 kB	✓
pages-turbo...prod.js gzip	21.9 kB	21.9 kB	✓
pages.runtim...dev.js gzip	22.6 kB	22.6 kB	✓
pages.runtim..prod.js gzip	21.9 kB	21.9 kB	✓
server.runti..prod.js gzip	49.6 kB	49.6 kB	✓
Overall change	941 kB	941 kB	✓

Commit: 7c34963

[timneutkens]

Changes look good. Can you update the PR description to reflect what we discussed 👍