fix(next): global not-found not working on multi-root layouts

[devjiwonchoi]

Why?

For multi-root layouts (route groups on the root with their root layouts, no layout file on the root), it is not possible to use global not-found since the layout is missing on the root.

.
└── app/
    ├── (main)/
    │   └── layout.js
    ├── (sub)/
    │   └── layout.js
    └── not-found.js --> ERR: missing layout

Current Behavior:

not-found.js doesn't have a root layout. To fix this error, make sure every page has a root layout.

What?

Let multi-root layouts also benefit from the global not-found.

How?

Wrap root not-found with default layout if root layout does not exist. Although this solution is not multi-root specific, it won't produce critical issues since a root layout is required for other cases.

Fixes #55191
Fixes #54980
Fixes #59180

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: 822776b

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: 012dc71

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer

[ijjk]

Stats from current PR

Default Build

General Overall increase ⚠️

	vercel/next.js canary	devjiwonchoi/next.js docs/multi-global-not-found	Change
buildDuration	13.7s	13.7s	N/A
buildDurationCached	7.3s	6.2s	N/A
nodeModulesSize	198 MB	198 MB	⚠️ +1.05 kB
nextStartRea..uration (ms)	431ms	442ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	devjiwonchoi/next.js docs/multi-global-not-found	Change
2453-HASH.js gzip	30.5 kB	30.5 kB	N/A
3304.HASH.js gzip	181 B	181 B	✓
3f784ff6-HASH.js gzip	53.7 kB	53.7 kB	N/A
8299-HASH.js gzip	5.04 kB	5.04 kB	N/A
framework-HASH.js gzip	45.2 kB	45.2 kB	✓
main-app-HASH.js gzip	242 B	241 B	N/A
main-HASH.js gzip	32.2 kB	32.2 kB	N/A
webpack-HASH.js gzip	1.68 kB	1.68 kB	N/A
Overall change	45.4 kB	45.4 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	devjiwonchoi/next.js docs/multi-global-not-found	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	devjiwonchoi/next.js docs/multi-global-not-found	Change
_app-HASH.js gzip	196 B	197 B	N/A
_error-HASH.js gzip	184 B	184 B	✓
amp-HASH.js gzip	505 B	505 B	✓
css-HASH.js gzip	324 B	325 B	N/A
dynamic-HASH.js gzip	2.5 kB	2.5 kB	N/A
edge-ssr-HASH.js gzip	258 B	258 B	✓
head-HASH.js gzip	352 B	352 B	✓
hooks-HASH.js gzip	370 B	371 B	N/A
image-HASH.js gzip	4.21 kB	4.21 kB	✓
index-HASH.js gzip	259 B	259 B	✓
link-HASH.js gzip	2.67 kB	2.67 kB	N/A
routerDirect..HASH.js gzip	314 B	312 B	N/A
script-HASH.js gzip	386 B	386 B	✓
withRouter-HASH.js gzip	309 B	309 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	6.57 kB	6.57 kB	✓

Client Build Manifests

	vercel/next.js canary	devjiwonchoi/next.js docs/multi-global-not-found	Change
_buildManifest.js gzip	481 B	484 B	N/A
Overall change	0 B	0 B	✓

Rendered Page Sizes

	vercel/next.js canary	devjiwonchoi/next.js docs/multi-global-not-found	Change
index.html gzip	528 B	529 B	N/A
link.html gzip	539 B	541 B	N/A
withRouter.html gzip	523 B	523 B	✓
Overall change	523 B	523 B	✓

Edge SSR bundle Size

	vercel/next.js canary	devjiwonchoi/next.js docs/multi-global-not-found	Change
edge-ssr.js gzip	95.1 kB	95.1 kB	N/A
page.js gzip	3.06 kB	3.07 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js canary	devjiwonchoi/next.js docs/multi-global-not-found	Change
middleware-b..fest.js gzip	626 B	624 B	N/A
middleware-r..fest.js gzip	151 B	151 B	✓
middleware.js gzip	25.5 kB	25.5 kB	N/A
edge-runtime..pack.js gzip	839 B	839 B	✓
Overall change	990 B	990 B	✓

Next Runtimes

	vercel/next.js canary	devjiwonchoi/next.js docs/multi-global-not-found	Change
app-page-exp...dev.js gzip	171 kB	171 kB	✓
app-page-exp..prod.js gzip	96.5 kB	96.5 kB	✓
app-page-tur..prod.js gzip	98.3 kB	98.3 kB	✓
app-page-tur..prod.js gzip	92.7 kB	92.7 kB	✓
app-page.run...dev.js gzip	149 kB	149 kB	✓
app-page.run..prod.js gzip	91.2 kB	91.2 kB	✓
app-route-ex...dev.js gzip	21.3 kB	21.3 kB	✓
app-route-ex..prod.js gzip	15 kB	15 kB	✓
app-route-tu..prod.js gzip	15 kB	15 kB	✓
app-route-tu..prod.js gzip	14.8 kB	14.8 kB	✓
app-route.ru...dev.js gzip	21 kB	21 kB	✓
app-route.ru..prod.js gzip	14.8 kB	14.8 kB	✓
pages-api-tu..prod.js gzip	9.52 kB	9.52 kB	✓
pages-api.ru...dev.js gzip	9.8 kB	9.8 kB	✓
pages-api.ru..prod.js gzip	9.52 kB	9.52 kB	✓
pages-turbo...prod.js gzip	22.3 kB	22.3 kB	✓
pages.runtim...dev.js gzip	22.9 kB	22.9 kB	✓
pages.runtim..prod.js gzip	22.3 kB	22.3 kB	✓
server.runti..prod.js gzip	50.5 kB	50.5 kB	✓
Overall change	948 kB	948 kB	✓

build cache

	vercel/next.js canary	devjiwonchoi/next.js docs/multi-global-not-found	Change
0.pack gzip	1.56 MB	1.56 MB	N/A
index.pack gzip	105 kB	105 kB	N/A
Overall change	0 B	0 B	✓

Diff details

Diff for middleware.js

Diff too large to display

Commit: caf0979

[devjiwonchoi]

It seems like Turbo is not generating a layout if it is missing one. I'll skip the test on turbo for now and will open a new issue for investigation.

[ijjk]

Tests Passed

[devjiwonchoi]

@shuding my bad, I didn't link the links below properly, didn't auto-close them:

#54980
#59180