Repository navigation
vitest 4 broke stubEnv(..., undefined) to unset an environment variable #10525
Description
Describe the bug
According to:
- feat(vi): allow env to be stubbed to undefined #6359
- https://github.com/vitest-dev/vitest/blob/main/docs/api/vi.md#vistubenv-vi-stubenv
I would expect
vi.stubEnv("foo", undefined);to delete process.env.foo.
This was working fine until vitest 4: now, passing undefined as value to stubEnv() doesn't seem to do anything anymore.
Reproduction
In this PR of a dedicated repo, you will see that the same test:
- passes in vitest 3
- fails in vitest 4
- fails in vitest 5-beta
The test fails in vitest 4 and 5-beta because the initial value of the environment variable remains after the call to stubEnv(..., undefined)
System Info
System:
OS: Linux 6.17 Ubuntu 24.04.4 LTS 24.04.4 LTS (Noble Numbat)
CPU: (4) x64 AMD EPYC 7763 64-Core Processor
Memory: 14.62 GB / 15.61 GB
Container: Yes
Shell: 5.2.21 - /bin/bash
Binaries:
Node: 24.16.0 - /opt/hostedtoolcache/node/24.16.0/x64/bin/node
Yarn: 1.22.22 - /usr/local/bin/yarn
npm: 11.13.0 - /opt/hostedtoolcache/node/24.16.0/x64/bin/npm
Browsers:
Chrome: 148.0.7778.178
Chromium: 148.0.7778.0
Firefox: 151.0.1
Firefox Developer Edition: 151.0.1
npmPackages:
vitest: ^4.1.8 => 4.1.8Used Package Manager
npm
Validations
- Follow our Code of Conduct
- Read the Contributing Guidelines.
- Read the docs.
- Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
- Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
- The provided reproduction is a minimal reproducible example of the bug.
Activity
clanzhang commentedon Jun 14, 2026
I'd like to work on this. PR soon.
DamienCassou commentedon Jul 1, 2026
@clanzhang did you find anything?
clanzhang commentedon Jul 1, 2026
Sorry for the delay! I've identified the root cause — the metaEnv Proxy in worker.ts has get/set traps that use the live process.env, but is missing a deleteProperty trap. When user code replaces process.env (e.g. process.env = {}), the delete in stubEnv(key, undefined) operates on the stale Proxy target instead of the current process.env.
The fix is to add a deleteProperty trap. Opening a PR now.
DamienCassou commentedon Jul 29, 2026
@clanzhang Have you opened a PR?
clanzhang commentedon Aug 3, 2026
Sorry, I don't really want to submit this PR — seeing that person gives me PTSD. Please don't rush me into submitting the PR either. Thanks.
Prajwal2246 commentedon Oct 7, 2026
Still happens on 5.0.3 (node 24.17.0) with the repro. Passes on 3.2.4, fails on 4.0.18 and later.
It only fails when process.env is reassigned (process.env = {}). Without that, stubEnv(key, undefined) works.
I tested adding a deleteProperty trap to the import.meta.env proxy in the installed vitest and the repro passed, so the cause clanzhang mentioned looks right. #10539 tried the same fix but was auto-closed. Would you accept a PR for this?