handle new hmr connection as heartbeat signal

[sokra]

and also automatically adjust ping interval to maxInactiveAge for cases where maxInactiveAge < 5s

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
buildDuration	12.7s	12.7s	-15ms
buildDurationCached	3.2s	2.9s	-257ms
nodeModulesSize	195 MB	195 MB	⚠️ +457 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.135	2.806	-0.33
/ avg req/sec	797.33	890.79	+93.46
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.373	1.333	-0.04
/error-in-render avg req/sec	1820.25	1875.53	+55.28

Client Bundles (main, webpack, commons)

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
779.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.2 kB	42.2 kB	✓
main-HASH.js gzip	26.9 kB	26.9 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	70.8 kB	70.8 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
polyfills-a4..dd70.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
_app-HASH.js gzip	977 B	977 B	✓
_error-HASH.js gzip	194 B	194 B	✓
amp-HASH.js gzip	311 B	311 B	✓
css-HASH.js gzip	328 B	328 B	✓
dynamic-HASH.js gzip	2.67 kB	2.67 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	918 B	918 B	✓
image-HASH.js gzip	4.12 kB	4.12 kB	✓
index-HASH.js gzip	260 B	260 B	✓
link-HASH.js gzip	1.66 kB	1.66 kB	✓
routerDirect..HASH.js gzip	320 B	320 B	✓
script-HASH.js gzip	386 B	386 B	✓
withRouter-HASH.js gzip	319 B	319 B	✓
bb14e60e810b..30f.css gzip	125 B	125 B	✓
Overall change	12.9 kB	12.9 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
_buildManifest.js gzip	494 B	494 B	✓
Overall change	494 B	494 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
index.html gzip	539 B	539 B	✓
link.html gzip	551 B	551 B	✓
withRouter.html gzip	533 B	533 B	✓
Overall change	1.62 kB	1.62 kB	✓

---

Default Build with SWC (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
buildDuration	6.3s	6.2s	-128ms
buildDurationCached	2.9s	3s	⚠️ +60ms
nodeModulesSize	195 MB	195 MB	⚠️ +457 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.86	2.844	-0.02
/ avg req/sec	874	879.17	+5.17
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.33	1.371	⚠️ +0.04
/error-in-render avg req/sec	1880.29	1822.88	⚠️ -57.41

Client Bundles (main, webpack, commons)

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
675-HASH.js gzip	13.8 kB	13.8 kB	✓
770.HASH.js gzip	178 B	178 B	✓
framework-HASH.js gzip	50.7 kB	50.7 kB	✓
main-HASH.js gzip	35 kB	35 kB	✓
webpack-HASH.js gzip	1.64 kB	1.64 kB	✓
Overall change	101 kB	101 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
polyfills-a4..dd70.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
_app-HASH.js gzip	1.33 kB	1.33 kB	✓
_error-HASH.js gzip	180 B	180 B	✓
amp-HASH.js gzip	315 B	315 B	✓
css-HASH.js gzip	331 B	331 B	✓
dynamic-HASH.js gzip	2.79 kB	2.79 kB	✓
head-HASH.js gzip	355 B	355 B	✓
hooks-HASH.js gzip	637 B	637 B	✓
image-HASH.js gzip	555 B	555 B	✓
index-HASH.js gzip	261 B	261 B	✓
link-HASH.js gzip	2.22 kB	2.22 kB	✓
routerDirect..HASH.js gzip	326 B	326 B	✓
script-HASH.js gzip	393 B	393 B	✓
withRouter-HASH.js gzip	322 B	322 B	✓
bb14e60e810b..30f.css gzip	125 B	125 B	✓
Overall change	10.1 kB	10.1 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
_buildManifest.js gzip	511 B	511 B	✓
Overall change	511 B	511 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js bugfix/hmr-ping	Change
index.html gzip	538 B	538 B	✓
link.html gzip	553 B	553 B	✓
withRouter.html gzip	533 B	533 B	✓
Overall change	1.62 kB	1.62 kB	✓

Commit: 7750cda

[ijjk]

Failing test suites

Commit: 7750cda

test/development/basic/hmr.test.ts

• basic HMR > Error Recovery > should recover from errors in the render function
• basic HMR > Error Recovery > should recover after exporting an invalid page
• basic HMR > Error Recovery > should recover after undefined exported as default

Expand output

● basic HMR › Error Recovery › should recover from errors in the render function

TIMED OUT: /This is the about page/

  437 |
  438 |   if (hardError) {
> 439 |     throw new Error('TIMED OUT: ' + regex + '\n\n' + content)
      |           ^
  440 |   }
  441 |   return false
  442 | }

  at Object.check (lib/next-test-utils.js:439:11)
  at Object.<anonymous> (development/basic/hmr.test.ts:455:9)

● basic HMR › Error Recovery › should recover after exporting an invalid page

TIMED OUT: /This is the about page/

  437 |
  438 |   if (hardError) {
> 439 |     throw new Error('TIMED OUT: ' + regex + '\n\n' + content)
      |           ^
  440 |   }
  441 |   return false
  442 | }

  at Object.check (lib/next-test-utils.js:439:11)
  at Object.<anonymous> (development/basic/hmr.test.ts:510:9)

● basic HMR › Error Recovery › should recover after undefined exported as default

TIMED OUT: /This is the about page/

  437 |
  438 |   if (hardError) {
> 439 |     throw new Error('TIMED OUT: ' + regex + '\n\n' + content)
      |           ^
  440 |   }
  441 |   return false
  442 | }

  at Object.check (lib/next-test-utils.js:439:11)
  at Object.<anonymous> (development/basic/hmr.test.ts:614:8)