Warn when inlining Vercel system env vars

[mischnic]

Part of PACK-6641

We don't have a way to silence (ignore-comment) warnings though
And additionally, warnings in node_modules are always hidden...

[mischnic]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Warn when inlining Vercel system env vars #89304 👈 (View in Graphite)
• Turbopack: FreeVarReference::ReportUsage #89302
• canary

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[lukesandberg]

why do we need to init these environment variables eagerly? if they don't exist then i guess they don't get replaced rather than an error?

leave a comment to that effect

[mischnic]

just for local testing for now, not sure yet if we are going to keep this

because these env vars are only when deploying, and not locally, which makes the DX worse

[lukesandberg]

yeah that makes sense

if we keep it, maybe consider a constant list of a strings in a loop?

[mischnic]

it's wrong to inline them with an empty string though
so i'm thinking about doing FreeVarReference::Warning { inner: None } instead to support warning but not replacing.

[mischnic]

With some more magic, it's now gated behind NOW_BUILDER like all other Vercel-specific stuff

But ideally, it would be printed in dev as well. Should we just always do this unconditionally? These are Vercel-specific env vars anyway?

[lukesandberg]

yeah i think doing it all the time is reasonable

[nextjs-bot]

Failing test suites

Commit: cbc6ad7 | About building and testing Next.js

pnpm test-start test/e2e/app-dir/app-prefetch/prefetching.test.ts (job)

• app dir - prefetching > should show layout eagerly when prefetched with loading one level down (DD)
• app dir - prefetching > should immediately render the loading state for a dynamic segment when fetched from higher up in the tree (DD)

Expand output

● app dir - prefetching › should show layout eagerly when prefetched with loading one level down

thrown: "Exceeded timeout of 120000 ms for a test.
Add a timeout value to this test to increase the timeout, if this is a long-running test. See https://jestjs.io/docs/api#testname-fn-timeout."

  26 |   })
  27 |
> 28 |   it('should show layout eagerly when prefetched with loading one level down', async () => {
     |   ^
  29 |     let act: ReturnType<typeof createRouterAct>
  30 |     const timeController = createTimeController()
  31 |     const browser = await next.browser('/', {

  at it (e2e/app-dir/app-prefetch/prefetching.test.ts:28:3)
  at Object.describe (e2e/app-dir/app-prefetch/prefetching.test.ts:11:1)

● app dir - prefetching › should immediately render the loading state for a dynamic segment when fetched from higher up in the tree

thrown: "Exceeded timeout of 120000 ms for a test.
Add a timeout value to this test to increase the timeout, if this is a long-running test. See https://jestjs.io/docs/api#testname-fn-timeout."

  302 |   })
  303 |
> 304 |   it('should immediately render the loading state for a dynamic segment when fetched from higher up in the tree', async () => {
      |   ^
  305 |     let act: ReturnType<typeof createRouterAct>
  306 |     const browser = await next.browser('/', {
  307 |       beforePageLoad(page) {

  at it (e2e/app-dir/app-prefetch/prefetching.test.ts:304:3)
  at Object.describe (e2e/app-dir/app-prefetch/prefetching.test.ts:11:1)

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing mischnic/system-env-warning (cbc6ad7) with canary (2e3fb9b)}

Summary

✅ 17 untouched benchmarks
⏩ 3 skipped benchmarks¹

Footnotes

1. 3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[nextjs-bot]

Stats from current PR

✅ No significant changes detected

📊 All Metrics

📖 Metrics Glossary

Dev Server Metrics:

• Listen = TCP port starts accepting connections
• First Request = HTTP server returns successful response
• Cold = Fresh build (no cache)
• Warm = With cached build artifacts

Build Metrics:

• Fresh = Clean build (no .next directory)
• Cached = With existing .next directory

Change Thresholds:

• Time: Changes < 50ms AND < 10%, OR < 2% are insignificant
• Size: Changes < 1KB AND < 1% are insignificant
• All other changes are flagged to catch regressions

⚡ Dev Server

Metric	Canary	PR	Change	Trend
Cold (Listen)	455ms	455ms	✓	▁▁▁▁▁
Cold (Ready in log)	438ms	438ms	✓	▁▂▂▂▂
Cold (First Request)	1.171s	1.168s	✓	▁▅▄▄▂
Warm (Listen)	455ms	456ms	✓	▁▁▁▁▁
Warm (Ready in log)	443ms	444ms	✓	▁▁▁▁▁
Warm (First Request)	340ms	342ms	✓	▁▂▁▂▂

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	455ms	455ms	✓	█▁███
Cold (Ready in log)	434ms	434ms	✓	▇▅▆▅▁
Cold (First Request)	1.827s	1.830s	✓	▅▃▃▄▁
Warm (Listen)	455ms	456ms	✓	▅█▅▅▅
Warm (Ready in log)	434ms	434ms	✓	▅▃▃▄▁
Warm (First Request)	1.821s	1.849s	✓	▅▃▃▃▁

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	3.887s	3.924s	✓	▂▁▁▁▃
Cached Build	3.921s	3.926s	✓	▂▁▁▁▃

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	13.631s	13.643s	✓	▄▁▁▂▁
Cached Build	13.686s	13.680s	✓	▄▁▁▂▁
node_modules Size	464 MB	464 MB	✓	███▁▁

📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles: **434 kB** → **434 kB** ✅ -2 B

81 files with content-based hashes (individual files not comparable between builds)

Server

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	762 B	768 B	✓
Total	762 B	768 B	⚠️ +6 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	450 B	451 B	✓
Total	450 B	451 B	⚠️ +1 B

📦 Webpack

Client

Main Bundles

	Canary	PR	Change
5528-HASH.js gzip	5.47 kB	N/A	-
6280-HASH.js gzip	54.5 kB	N/A	-
6335.HASH.js gzip	169 B	N/A	-
912-HASH.js gzip	4.53 kB	N/A	-
e8aec2e4-HASH.js gzip	62.5 kB	N/A	-
framework-HASH.js gzip	59.7 kB	59.7 kB	✓
main-app-HASH.js gzip	256 B	253 B	🟢 3 B (-1%)
main-HASH.js gzip	39 kB	39 kB	✓
webpack-HASH.js gzip	1.68 kB	1.68 kB	✓
262-HASH.js gzip	N/A	4.52 kB	-
2889.HASH.js gzip	N/A	169 B	-
5602-HASH.js gzip	N/A	5.48 kB	-
6948ada0-HASH.js gzip	N/A	62.5 kB	-
9544-HASH.js gzip	N/A	55.2 kB	-
Total	228 kB	228 kB	⚠️ +670 B

Polyfills

	Canary	PR	Change
polyfills-HASH.js gzip	39.4 kB	39.4 kB	✓
Total	39.4 kB	39.4 kB	✓

Pages

	Canary	PR	Change
_app-HASH.js gzip	194 B	194 B	✓
_error-HASH.js gzip	183 B	180 B	🟢 3 B (-2%)
css-HASH.js gzip	331 B	330 B	✓
dynamic-HASH.js gzip	1.81 kB	1.81 kB	✓
edge-ssr-HASH.js gzip	256 B	256 B	✓
head-HASH.js gzip	351 B	352 B	✓
hooks-HASH.js gzip	384 B	383 B	✓
image-HASH.js gzip	580 B	581 B	✓
index-HASH.js gzip	260 B	260 B	✓
link-HASH.js gzip	2.49 kB	2.49 kB	✓
routerDirect..HASH.js gzip	320 B	319 B	✓
script-HASH.js gzip	386 B	386 B	✓
withRouter-HASH.js gzip	315 B	315 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Total	7.97 kB	7.97 kB	✅ -1 B

Server

Edge SSR

	Canary	PR	Change
edge-ssr.js gzip	126 kB	126 kB	✓
page.js gzip	248 kB	249 kB	✓
Total	375 kB	375 kB	⚠️ +119 B

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	615 B	612 B	✓
middleware-r..fest.js gzip	156 B	155 B	✓
middleware.js gzip	33.1 kB	33.1 kB	✓
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	34.7 kB	34.8 kB	⚠️ +34 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	732 B	736 B	✓
Total	732 B	736 B	⚠️ +4 B

Build Cache

	Canary	PR	Change
0.pack gzip	3.79 MB	3.8 MB	🔴 +10.6 kB (+0%)
index.pack gzip	102 kB	102 kB	✓
index.pack.old gzip	103 kB	103 kB	✓
Total	4 MB	4.01 MB	⚠️ +10.6 kB

🔄 Shared (bundler-independent)

Runtimes

	Canary	PR	Change
app-page-exp...dev.js gzip	311 kB	311 kB	✓
app-page-exp..prod.js gzip	166 kB	166 kB	✓
app-page-tur...dev.js gzip	311 kB	311 kB	✓
app-page-tur..prod.js gzip	166 kB	166 kB	✓
app-page-tur...dev.js gzip	308 kB	308 kB	✓
app-page-tur..prod.js gzip	164 kB	164 kB	✓
app-page.run...dev.js gzip	308 kB	308 kB	✓
app-page.run..prod.js gzip	164 kB	164 kB	✓
app-route-ex...dev.js gzip	70.4 kB	70.4 kB	✓
app-route-ex..prod.js gzip	48.9 kB	48.9 kB	✓
app-route-tu...dev.js gzip	70.4 kB	70.4 kB	✓
app-route-tu..prod.js gzip	49 kB	49 kB	✓
app-route-tu...dev.js gzip	70 kB	70 kB	✓
app-route-tu..prod.js gzip	48.7 kB	48.7 kB	✓
app-route.ru...dev.js gzip	70 kB	70 kB	✓
app-route.ru..prod.js gzip	48.7 kB	48.7 kB	✓
dist_client_...dev.js gzip	324 B	324 B	✓
dist_client_...dev.js gzip	326 B	326 B	✓
dist_client_...dev.js gzip	318 B	318 B	✓
dist_client_...dev.js gzip	317 B	317 B	✓
pages-api-tu...dev.js gzip	43.1 kB	43.1 kB	✓
pages-api-tu..prod.js gzip	32.9 kB	32.9 kB	✓
pages-api.ru...dev.js gzip	43.1 kB	43.1 kB	✓
pages-api.ru..prod.js gzip	32.8 kB	32.8 kB	✓
pages-turbo....dev.js gzip	52.4 kB	52.4 kB	✓
pages-turbo...prod.js gzip	39.4 kB	39.4 kB	✓
pages.runtim...dev.js gzip	52.4 kB	52.4 kB	✓
pages.runtim..prod.js gzip	39.3 kB	39.3 kB	✓
server.runti..prod.js gzip	62.5 kB	62.5 kB	✓
Total	2.77 MB	2.77 MB	✓