Describe the bug

When building a project that uses import.meta.env.UNKNOWN, it is being replaced as MODE:"production",DEV:!1,PROD:!0}.UNKNOWN instead of ({}).UNKNOWN.

Ref #8090 (Additional context)

Bug introduced in #5972 in Vite 3. Line 50 is never being used, and skips to line 51 instead.

This not only happens for import.meta.env., but process.env. to for ssr builds. And other similar usage.

Reproduction

Vite 3: https://stackblitz.com/edit/vitejs-vite-b1md2x?file=main.js&terminal=build,preview
Vite 2.9: https://stackblitz.com/edit/vitejs-vite-ouwh65?file=main.js&terminal=build,preview

System Info

Vite 3

Used Package Manager

pnpm

Logs

No response

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.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to https://github.com/vuejs/core instead.
• 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.