Ensure decode error in minimal mode responds with 400 not 500

[ijjk]

This ensures we handle decode failures in minimal mode as a 400 response (bad request) instead of a 500 (server error).

Bug

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

[ijjk]

Stats from current PR

Default Build (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	ijjk/next.js fix/minimal-400-handling	Change
buildDuration	21.4s	21.4s	⚠️ +60ms
buildDurationCached	4.3s	4.3s	⚠️ +23ms
nodeModulesSize	332 MB	332 MB	⚠️ +703 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	ijjk/next.js fix/minimal-400-handling	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.455	3.572	⚠️ +0.12
/ avg req/sec	723.6	699.83	⚠️ -23.77
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.646	1.721	⚠️ +0.08
/error-in-render avg req/sec	1518.5	1452.41	⚠️ -66.09

Client Bundles (main, webpack, commons)

	vercel/next.js canary	ijjk/next.js fix/minimal-400-handling	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.2 kB	42.2 kB	✓
main-HASH.js gzip	28 kB	28 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	71.9 kB	71.9 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	ijjk/next.js fix/minimal-400-handling	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/minimal-400-handling	Change
_app-HASH.js gzip	1.23 kB	1.23 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	✓
334f979574ae..6f4.css gzip	106 B	106 B	✓
Overall change	13.1 kB	13.1 kB	✓

Client Build Manifests

	vercel/next.js canary	ijjk/next.js fix/minimal-400-handling	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/minimal-400-handling	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 increase ⚠️

	vercel/next.js canary	ijjk/next.js fix/minimal-400-handling	Change
buildDuration	23.1s	23.9s	⚠️ +767ms
buildDurationCached	4.5s	4.7s	⚠️ +159ms
nodeModulesSize	332 MB	332 MB	⚠️ +703 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	ijjk/next.js fix/minimal-400-handling	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.631	3.641	⚠️ +0.01
/ avg req/sec	688.54	686.6	⚠️ -1.94
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.665	1.786	⚠️ +0.12
/error-in-render avg req/sec	1501.46	1399.93	⚠️ -101.53

Client Bundles (main, webpack, commons)

	vercel/next.js canary	ijjk/next.js fix/minimal-400-handling	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.3 kB	42.3 kB	✓
main-HASH.js gzip	28.2 kB	28.2 kB	✓
webpack-HASH.js gzip	1.43 kB	1.43 kB	✓
Overall change	72.1 kB	72.1 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	ijjk/next.js fix/minimal-400-handling	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/minimal-400-handling	Change
_app-HASH.js gzip	1.22 kB	1.22 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	✓
334f979574ae..6f4.css gzip	106 B	106 B	✓
Overall change	13.1 kB	13.1 kB	✓

Client Build Manifests

	vercel/next.js canary	ijjk/next.js fix/minimal-400-handling	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/minimal-400-handling	Change
index.html gzip	521 B	521 B	✓
link.html gzip	534 B	534 B	✓
withRouter.html gzip	515 B	515 B	✓
Overall change	1.57 kB	1.57 kB	✓

Commit: 659f3b0