Add eslint rule to prevent importing next/server outside of _middleware

[thibautsabot]

Fixes #30921

Based on https://nextjs.org/docs/messages/no-document-import-in-page

[ijjk]

Stats from current PR

Default Build (Decrease detected ✓)

General Overall decrease ✓

	vercel/next.js canary	thibautsabot/next.js no-server-import-in-pages	Change
buildDuration	22.1s	22.3s	⚠️ +155ms
buildDurationCached	4.3s	4.6s	⚠️ +255ms
nodeModulesSize	335 MB	335 MB	-13 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	thibautsabot/next.js no-server-import-in-pages	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.642	3.64	0
/ avg req/sec	686.36	686.89	+0.53
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.617	1.703	⚠️ +0.09
/error-in-render avg req/sec	1545.81	1468	⚠️ -77.81

Client Bundles (main, webpack, commons)

	vercel/next.js canary	thibautsabot/next.js no-server-import-in-pages	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	thibautsabot/next.js no-server-import-in-pages	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	thibautsabot/next.js no-server-import-in-pages	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	4.44 kB	4.44 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	thibautsabot/next.js no-server-import-in-pages	Change
_buildManifest.js gzip	460 B	460 B	✓
Overall change	460 B	460 B	✓

Rendered Page Sizes

	vercel/next.js canary	thibautsabot/next.js no-server-import-in-pages	Change
index.html gzip	522 B	522 B	✓
link.html gzip	535 B	535 B	✓
withRouter.html gzip	515 B	515 B	✓
Overall change	1.57 kB	1.57 kB	✓

---

Default Build with SWC (Decrease detected ✓)

General Overall decrease ✓

	vercel/next.js canary	thibautsabot/next.js no-server-import-in-pages	Change
buildDuration	23.6s	24s	⚠️ +425ms
buildDurationCached	4.4s	4.4s	⚠️ +68ms
nodeModulesSize	335 MB	335 MB	-13 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	thibautsabot/next.js no-server-import-in-pages	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.58	3.63	⚠️ +0.05
/ avg req/sec	698.28	688.78	⚠️ -9.5
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.733	1.759	⚠️ +0.03
/error-in-render avg req/sec	1442.67	1421.28	⚠️ -21.39

Client Bundles (main, webpack, commons)

	vercel/next.js canary	thibautsabot/next.js no-server-import-in-pages	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.3 kB	42.3 kB	✓
main-HASH.js gzip	28.5 kB	28.5 kB	✓
webpack-HASH.js gzip	1.43 kB	1.43 kB	✓
Overall change	72.5 kB	72.5 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	thibautsabot/next.js no-server-import-in-pages	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	thibautsabot/next.js no-server-import-in-pages	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	4.46 kB	4.46 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	thibautsabot/next.js no-server-import-in-pages	Change
_buildManifest.js gzip	459 B	459 B	✓
Overall change	459 B	459 B	✓

Rendered Page Sizes

	vercel/next.js canary	thibautsabot/next.js no-server-import-in-pages	Change
index.html gzip	522 B	522 B	✓
link.html gzip	534 B	534 B	✓
withRouter.html gzip	516 B	516 B	✓
Overall change	1.57 kB	1.57 kB	✓

Commit: 061f580

[ijjk]

Thanks for the PR!

[ljosberinn]

@thibautsabot It appears this has been released, however the rule is not included within the plugin as per index.js. Care to add it there aswell? :)

[ykzts]

@thibautsabot Is it a deliberate behavior to get errors in non-root _middleware.ts like /pages/about/_middleware.ts and /pages/about/team/_middleware.ts?

[ljosberinn]

sounds like an issue with this line. Any path that includes /pages would be a valid path?

[thibautsabot]

Hello!

Sorry for the inconvenience, will take a loot at it later today!