fix(route-handlers): make sure preflight has CORS headers

[samcx]

Why?

When we just have a POST route handler, it seems CORs is not working properly. This is because we break out of the loop here

next.js/packages/next/src/server/future/route-modules/app-route/helpers/auto-implement-methods.ts

Line 38 in 768a92b

if (!handlers.GET) break

when a GET isn't present before we add the correct headers and status to the preflight OPTION.

• Closes Route Handler has CORS errors if GET is not present #57999

Closes NEXT-2813

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General

	vercel/next.js canary	samcx/next.js sam/route-handlers/cors-fix	Change
buildDuration	14.3s	14.4s	⚠️ +114ms
buildDurationCached	7.9s	6.8s	N/A
nodeModulesSize	198 MB	198 MB	N/A
nextStartRea..uration (ms)	452ms	436ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	samcx/next.js sam/route-handlers/cors-fix	Change
2453-HASH.js gzip	30.4 kB	30.4 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	242 B	✓
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	45.6 kB	45.6 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	samcx/next.js sam/route-handlers/cors-fix	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	samcx/next.js sam/route-handlers/cors-fix	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	samcx/next.js sam/route-handlers/cors-fix	Change
_buildManifest.js gzip	481 B	484 B	N/A
Overall change	0 B	0 B	✓

Rendered Page Sizes

	vercel/next.js canary	samcx/next.js sam/route-handlers/cors-fix	Change
index.html gzip	529 B	529 B	✓
link.html gzip	542 B	541 B	N/A
withRouter.html gzip	525 B	523 B	N/A
Overall change	529 B	529 B	✓

Edge SSR bundle Size

	vercel/next.js canary	samcx/next.js sam/route-handlers/cors-fix	Change
edge-ssr.js gzip	95.1 kB	95.1 kB	N/A
page.js gzip	3.05 kB	3.05 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js canary	samcx/next.js sam/route-handlers/cors-fix	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	samcx/next.js sam/route-handlers/cors-fix	Change
app-page-exp...dev.js gzip	171 kB	171 kB	✓
app-page-exp..prod.js gzip	96.6 kB	96.6 kB	✓
app-page-tur..prod.js gzip	98.3 kB	98.3 kB	✓
app-page-tur..prod.js gzip	92.8 kB	92.8 kB	✓
app-page.run...dev.js gzip	149 kB	149 kB	✓
app-page.run..prod.js gzip	91.3 kB	91.3 kB	✓
app-route-ex...dev.js gzip	21.3 kB	21.3 kB	N/A
app-route-ex..prod.js gzip	15 kB	15 kB	N/A
app-route-tu..prod.js gzip	15 kB	15 kB	N/A
app-route-tu..prod.js gzip	14.8 kB	14.8 kB	N/A
app-route.ru...dev.js gzip	21 kB	21 kB	N/A
app-route.ru..prod.js gzip	14.8 kB	14.8 kB	N/A
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	50.6 kB	50.6 kB	✓
Overall change	846 kB	846 kB	✓

build cache Overall increase ⚠️

	vercel/next.js canary	samcx/next.js sam/route-handlers/cors-fix	Change
0.pack gzip	1.56 MB	1.56 MB	N/A
index.pack gzip	105 kB	106 kB	⚠️ +546 B
Overall change	105 kB	106 kB	⚠️ +546 B

Diff details

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Commit: 6c4a1c5

[ijjk]

Failing test suites

Commit: f3f8284

pnpm test-dev test/e2e/app-dir/edge-runtime-node-compatibility/edge-runtime-node-compatibility.test.ts (PPR)

• edge runtime node compatibility > [app] supports node:buffer

Expand output

● edge runtime node compatibility › [app] supports node:buffer

FetchError: invalid json response body at http://localhost:40037/buffer reason: Unexpected token '<', "<!DOCTYPE "... is not valid JSON

  12 |         body: 'Hello, world!',
  13 |       })
> 14 |       const json = await res.json()
     |                    ^
  15 |       expect(json).toEqual({
  16 |         'Buffer === B.Buffer': true,
  17 |         encoded: Buffer.from('Hello, world!').toString('base64'),

  at ../node_modules/.pnpm/node-fetch@2.6.7/node_modules/node-fetch/lib/index.js:273:32
  at Object.<anonymous> (e2e/app-dir/edge-runtime-node-compatibility/edge-runtime-node-compatibility.test.ts:14:20)

Read more about building and testing Next.js in contributing.md.

[ijjk]

Good catch, test and change looks good