Fix middleware types with skipLibCheck: false

[ijjk]

This ensures type checking passes correctly for middleware types when skipLibCheck: false is set in tsconfig.json. This also moves the middleware-types to be an isolated test to ensure it isn't relying on any monorepo dependencies.

Bug

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

Fixes: #31992 (comment)

[ijjk]

Stats from current PR

Default Build (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	ijjk/next.js fix/middleware-types-lib-check	Change
buildDuration	24.1s	24.4s	⚠️ +311ms
buildDurationCached	4.3s	4.3s	-14ms
nodeModulesSize	347 MB	347 MB	⚠️ +227 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	ijjk/next.js fix/middleware-types-lib-check	Change
/ failed reqs	0	0	✓
/ total time (seconds)	4.146	4.048	-0.1
/ avg req/sec	603.04	617.55	+14.51
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	2.129	2.207	⚠️ +0.08
/error-in-render avg req/sec	1174.3	1132.97	⚠️ -41.33

Client Bundles (main, webpack, commons)

	vercel/next.js canary	ijjk/next.js fix/middleware-types-lib-check	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.2 kB	42.2 kB	✓
main-HASH.js gzip	28.4 kB	28.4 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	72.3 kB	72.3 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	ijjk/next.js fix/middleware-types-lib-check	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/middleware-types-lib-check	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	326 B	326 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	4.49 kB	4.49 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/middleware-types-lib-check	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/middleware-types-lib-check	Change
index.html gzip	532 B	532 B	✓
link.html gzip	545 B	545 B	✓
withRouter.html gzip	527 B	527 B	✓
Overall change	1.6 kB	1.6 kB	✓

---

Default Build with SWC (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	ijjk/next.js fix/middleware-types-lib-check	Change
buildDuration	26.5s	26.5s	-18ms
buildDurationCached	4.3s	4.3s	⚠️ +40ms
nodeModulesSize	347 MB	347 MB	⚠️ +227 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	ijjk/next.js fix/middleware-types-lib-check	Change
/ failed reqs	0	0	✓
/ total time (seconds)	4.022	4.051	⚠️ +0.03
/ avg req/sec	621.6	617.08	⚠️ -4.52
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	2.157	2.163	⚠️ +0.01
/error-in-render avg req/sec	1159.25	1155.93	⚠️ -3.32

Client Bundles (main, webpack, commons)

	vercel/next.js canary	ijjk/next.js fix/middleware-types-lib-check	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/middleware-types-lib-check	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/middleware-types-lib-check	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	2.37 kB	2.37 kB	✓
head-HASH.js gzip	342 B	342 B	✓
hooks-HASH.js gzip	622 B	622 B	✓
image-HASH.js gzip	4.53 kB	4.53 kB	✓
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	1.9 kB	1.9 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	13.3 kB	13.3 kB	✓

Client Build Manifests

	vercel/next.js canary	ijjk/next.js fix/middleware-types-lib-check	Change
_buildManifest.js gzip	458 B	458 B	✓
Overall change	458 B	458 B	✓

Rendered Page Sizes

	vercel/next.js canary	ijjk/next.js fix/middleware-types-lib-check	Change
index.html gzip	531 B	531 B	✓
link.html gzip	545 B	545 B	✓
withRouter.html gzip	525 B	525 B	✓
Overall change	1.6 kB	1.6 kB	✓

Commit: e33525a