Webpack loaders that mutate `process.env` at build time not supported
#1 500 ouverte le 22 mai 2026
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Description
This issue was created by an agent analysing CI failures from the Next.js Deploy Suite (vinext
mainvs Next.jsv16.2.6, 2026-05-22).
Problem
Next.js allows webpack loaders to set environment variables during the build (e.g. via process.env.X = ...), which then become available in user code. vinext (Vite/Rolldown-based) does not run webpack loaders, so these env vars are absent and the test app renders the default error page.
Webpack loader sets process.env.X at build time; user code reads undefined
Estimated Impact
~1 test failures across the deploy suite.
Affected Test Suites
test/e2e/app-dir/webpack-loader-set-environment-variable/webpack-loader-set-environment-variable.test.ts
Recommendation
-
Reproduce first in vinext's own test suite. Add a fixture with a webpack loader that sets
process.env.MY_VARand a page that printsprocess.env.MY_VAR. Confirm the page does not see the value. -
Decide on a vinext equivalent. Either implement a Vite plugin that runs at build start and can mutate the
definemap, or document that webpack loaders are not portable. Update fixture / triage decision accordingly.