[ESLint] Adds temporary error message for ESLint v8

[housseindjirdeh]

ESLint v8 is not yet supported and there's an open PR (#29865) to include it. Before this can land, all the plugins and libraries used by eslint-config-next will first need to support it. This PR introduces a temporary error message to inform developers to downgrade to v7 for the meantime.

Note: This will help clear some confusion until v8 is supported (see #30062, #30105, #29977, #29961).

[ijjk]

Thanks!

[ijjk]

Stats from current PR

Default Build (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
buildDuration	11.7s	11.9s	⚠️ +183ms
buildDurationCached	2.7s	2.8s	⚠️ +115ms
nodeModulesSize	195 MB	195 MB	⚠️ +1.14 kB

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.713	2.72	⚠️ +0.01
/ avg req/sec	921.39	919.13	⚠️ -2.26
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.335	1.34	⚠️ +0.01
/error-in-render avg req/sec	1873.22	1865.06	⚠️ -8.16

Client Bundles (main, webpack, commons)

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
651.cd440d20..0b23.js gzip	2.96 kB	2.96 kB	✓
831.695e33f6..205f.js gzip	179 B	179 B	✓
framework-89..a097.js gzip	42.2 kB	42.2 kB	✓
main-45201df..96b4.js gzip	26.1 kB	26.1 kB	✓
webpack-f09b..493e.js gzip	1.47 kB	1.47 kB	✓
Overall change	73 kB	73 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
polyfills-a4..dd70.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
_app-9fb8765..c13d.js gzip	979 B	979 B	✓
_error-d828d..2954.js gzip	3.06 kB	3.06 kB	✓
amp-5388d1f5..4ce9.js gzip	551 B	551 B	✓
css-10424225..367a.js gzip	329 B	329 B	✓
dynamic-9821..3cd4.js gzip	2.67 kB	2.67 kB	✓
head-1df323b..d261.js gzip	2.32 kB	2.32 kB	✓
hooks-ab0016..b093.js gzip	917 B	917 B	✓
image-c3cc30..4e2a.js gzip	5.87 kB	5.87 kB	✓
index-95c8cb..6970.js gzip	260 B	260 B	✓
link-05c99e7..35ec.js gzip	1.66 kB	1.66 kB	✓
routerDirect..6659.js gzip	319 B	319 B	✓
script-d94ba..ed05.js gzip	386 B	386 B	✓
withRouter-7..8b2e.js gzip	317 B	317 B	✓
9a34b27eb3f9..27d.css gzip	125 B	125 B	✓
Overall change	19.8 kB	19.8 kB	✓

Client Build Manifests

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
_buildManifest.js gzip	458 B	458 B	✓
Overall change	458 B	458 B	✓

Rendered Page Sizes

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
index.html gzip	537 B	537 B	✓
link.html gzip	549 B	549 B	✓
withRouter.html gzip	529 B	529 B	✓
Overall change	1.61 kB	1.61 kB	✓

---

Default Build with SWC (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
buildDuration	5.7s	5.9s	⚠️ +154ms
buildDurationCached	2.7s	2.8s	⚠️ +129ms
nodeModulesSize	195 MB	195 MB	⚠️ +1.14 kB

Page Load Tests Overall increase ✓

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.845	2.739	-0.11
/ avg req/sec	878.61	912.77	+34.16
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.346	1.278	-0.07
/error-in-render avg req/sec	1857.68	1955.95	+98.27

Client Bundles (main, webpack, commons)

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
450.fd3ad245..022b.js gzip	179 B	179 B	✓
675-f623fa2a..036a.js gzip	13.9 kB	13.9 kB	✓
framework-13..70b0.js gzip	50.8 kB	50.8 kB	✓
main-1e4b9db..ad07.js gzip	36.5 kB	36.5 kB	✓
webpack-a7f2..2650.js gzip	1.63 kB	1.63 kB	✓
Overall change	103 kB	103 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
polyfills-a4..dd70.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
_app-ae91bc3..d985.js gzip	1.33 kB	1.33 kB	✓
_error-273ac..9ef0.js gzip	180 B	180 B	✓
amp-5f9a7694..99ce.js gzip	315 B	315 B	✓
css-3a1b2477..df1e.js gzip	330 B	330 B	✓
dynamic-8d0e..e365.js gzip	2.79 kB	2.79 kB	✓
head-7f600d0..daa3.js gzip	356 B	356 B	✓
hooks-bd8c02..0730.js gzip	638 B	638 B	✓
image-16df09..4584.js gzip	555 B	555 B	✓
index-80be94..e89f.js gzip	262 B	262 B	✓
link-4ee1ea7..8745.js gzip	2.22 kB	2.22 kB	✓
routerDirect..c4aa.js gzip	325 B	325 B	✓
script-67da0..49e6.js gzip	390 B	390 B	✓
withRouter-2..2409.js gzip	322 B	322 B	✓
9a34b27eb3f9..27d.css gzip	125 B	125 B	✓
Overall change	10.1 kB	10.1 kB	✓

Client Build Manifests

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
_buildManifest.js gzip	476 B	476 B	✓
Overall change	476 B	476 B	✓

Rendered Page Sizes

	vercel/next.js canary	housseindjirdeh/next.js adds-temporary-eslint-v8-error	Change
index.html gzip	534 B	534 B	✓
link.html gzip	545 B	545 B	✓
withRouter.html gzip	526 B	526 B	✓
Overall change	1.6 kB	1.6 kB	✓

Commit: f49912b

[ijjk]

Failing test suites

Commit: f49912b

test/development/basic-basepath/hmr.test.ts

• basic HMR > Error Recovery > should recover after exporting an invalid page
• basic HMR > Error Recovery > should recover after a bad return from the render function
• basic HMR > Error Recovery > should recover after undefined exported as default

Expand output

● basic HMR › Error Recovery › should recover after exporting an invalid page

expect(received).toMatchInlineSnapshot(snapshot)

Snapshot name: `basic HMR Error Recovery should recover after exporting an invalid page 1`

- Snapshot  - 3
+ Received  + 1

   1 of 1 unhandled error
- Server Error
+ Unhandled Runtime Error

  Error: The default export is not a React Component in page: "/hmr/about5"
-
- This error happened while generating the page. Any console logs will be displayed in the terminal window.

  491 |
  492 |         expect(await hasRedbox(browser)).toBe(true)
> 493 |         expect(await getRedboxHeader(browser)).toMatchInlineSnapshot(`
      |                                                ^
  494 |           " 1 of 1 unhandled error
  495 |           Server Error
  496 |

  at Object.<anonymous> (development/basic-basepath/hmr.test.ts:493:48)

● basic HMR › Error Recovery › should recover after a bad return from the render function

TIMED OUT: /This is the about page/

  437 |
  438 |   if (hardError) {
> 439 |     throw new Error('TIMED OUT: ' + regex + '\n\n' + content)
      |           ^
  440 |   }
  441 |   return false
  442 | }

  at Object.check (lib/next-test-utils.js:439:11)
  at Object.<anonymous> (development/basic-basepath/hmr.test.ts:561:9)

● basic HMR › Error Recovery › should recover after undefined exported as default

TIMED OUT: /This is the about page/

  437 |
  438 |   if (hardError) {
> 439 |     throw new Error('TIMED OUT: ' + regex + '\n\n' + content)
      |           ^
  440 |   }
  441 |   return false
  442 | }

  at Object.check (lib/next-test-utils.js:439:11)
  at Object.<anonymous> (development/basic-basepath/hmr.test.ts:617:8)

● basic HMR › Error Recovery › should recover after undefined exported as default

expect(received).toMatchInlineSnapshot(snapshot)

Snapshot name: `basic HMR Error Recovery should recover after undefined exported as default 1`

- Snapshot  - 3
+ Received  + 1

   1 of 1 unhandled error
- Server Error
+ Unhandled Runtime Error

  Error: The default export is not a React Component in page: "/hmr/about7"
-
- This error happened while generating the page. Any console logs will be displayed in the terminal window.

  603 |         await next.patchFile(aboutPage, aboutContent)
  604 |
> 605 |         if (browser) {
      |                       ^
  606 |           await check(
  607 |             () => getBrowserBodyText(browser),
  608 |             /This is the about page/

  at Object.<anonymous> (development/basic-basepath/hmr.test.ts:605:23)