Fix accessing router before ready for HMR ping

[ijjk]

This ensures we don't attempt accessing the router for the HMR ping before the router is ready. This also fixes an issue that previously existed where AMP pages weren't pinging due to Router.ready never being called client-side. Also an un-necessary eslint config in test/.eslintrc was removed as we are properly applying lint rules to test files in the main .eslintrc file and the extra one causes conflicts.

Bug

• Related issues linked using fixes #number
• Integration tests added
• Errors have helpful link attached, see contributing.md

Fixes: #30710

[ijjk]

Stats from current PR

Default Build (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
buildDuration	18s	17.7s	-360ms
buildDurationCached	3.5s	3.3s	-265ms
nodeModulesSize	338 MB	338 MB	⚠️ +780 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.03	3.04	⚠️ +0.01
/ avg req/sec	825.1	822.34	⚠️ -2.76
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.392	1.461	⚠️ +0.07
/error-in-render avg req/sec	1795.83	1711.37	⚠️ -84.46

Client Bundles (main, webpack, commons)

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.2 kB	42.2 kB	✓
main-HASH.js gzip	28.3 kB	28.3 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	72.2 kB	72.2 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
_app-HASH.js gzip	1.37 kB	1.37 kB	✓
_error-HASH.js gzip	194 B	194 B	✓
amp-HASH.js gzip	312 B	312 B	✓
css-HASH.js gzip	327 B	327 B	✓
dynamic-HASH.js gzip	2.38 kB	2.38 kB	✓
head-HASH.js gzip	350 B	350 B	✓
hooks-HASH.js gzip	635 B	635 B	✓
image-HASH.js gzip	4.45 kB	4.45 kB	✓
index-HASH.js gzip	263 B	263 B	✓
link-HASH.js gzip	1.87 kB	1.87 kB	✓
routerDirect..HASH.js gzip	321 B	321 B	✓
script-HASH.js gzip	383 B	383 B	✓
withRouter-HASH.js gzip	318 B	318 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	13.3 kB	13.3 kB	✓

Client Build Manifests

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
_buildManifest.js gzip	460 B	460 B	✓
Overall change	460 B	460 B	✓

Rendered Page Sizes

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
index.html gzip	522 B	522 B	✓
link.html gzip	535 B	535 B	✓
withRouter.html gzip	517 B	517 B	✓
Overall change	1.57 kB	1.57 kB	✓

---

Default Build with SWC (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
buildDuration	17.8s	18s	⚠️ +232ms
buildDurationCached	3.3s	3.4s	⚠️ +86ms
nodeModulesSize	338 MB	338 MB	⚠️ +780 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.89	2.81	-0.08
/ avg req/sec	865.02	889.67	+24.65
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.31	1.322	⚠️ +0.01
/error-in-render avg req/sec	1908.1	1891.29	⚠️ -16.81

Client Bundles (main, webpack, commons)

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.3 kB	42.3 kB	✓
main-HASH.js gzip	28.6 kB	28.6 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	72.5 kB	72.5 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
_app-HASH.js gzip	1.35 kB	1.35 kB	✓
_error-HASH.js gzip	180 B	180 B	✓
amp-HASH.js gzip	305 B	305 B	✓
css-HASH.js gzip	321 B	321 B	✓
dynamic-HASH.js gzip	2.38 kB	2.38 kB	✓
head-HASH.js gzip	342 B	342 B	✓
hooks-HASH.js gzip	622 B	622 B	✓
image-HASH.js gzip	4.47 kB	4.47 kB	✓
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	1.91 kB	1.91 kB	✓
routerDirect..HASH.js gzip	314 B	314 B	✓
script-HASH.js gzip	375 B	375 B	✓
withRouter-HASH.js gzip	309 B	309 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	13.2 kB	13.2 kB	✓

Client Build Manifests

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
_buildManifest.js gzip	459 B	459 B	✓
Overall change	459 B	459 B	✓

Rendered Page Sizes

	vercel/next.js canary	ijjk/next.js fix/no-router-instance	Change
index.html gzip	523 B	523 B	✓
link.html gzip	536 B	536 B	✓
withRouter.html gzip	517 B	517 B	✓
Overall change	1.58 kB	1.58 kB	✓

Commit: 4ae1578