Tree-shaking not working in v3 beta

[bysja]

Describe the bug

I upgraded Vite to 3.0.0-beta.0 to resolve this issue, which prevents me from using v2.9 right now.

However, tree-shaking fails for every library I import in v3, despite working properly in v2.9.

The reproduction example imports a single icon from an external library (@heroicons/react) with the following JS bundle sizes when runing vite build:

v3.0.0-beta.0 / @vitejs/plugin-react v2.0.0-beta.0
239.07 KiB / gzip: 60.83 KiB

v2.9.12 / @vitejs/plugin-react v1.3.2
140.52 KiB / gzip: 45.34 KiB

The v3 repo is attached in the reproduction link.

Here is the v2.9 repo for comparison: https://github.com/bysja/vitejs-vite-v2-treeshaking

Reproduction

https://github.com/bysja/vitejs-vite-v3-treeshaking

System Info

Default StackBlitz environment

Used Package Manager

npm

Logs

v3
❯ npm run build
$ vite build
vite v3.0.0-beta.0 building for production...
✓ 14 modules transformed.
dist/assets/react.35ef61ed.svg 4.03 KiB
dist/index.html 0.44 KiB
dist/assets/index.3fce1f81.css 1.37 KiB / gzip: 0.71 KiB
dist/assets/index.eebf1dba.js 239.07 KiB / gzip: 60.83 KiB

v2.9
❯ npm run build
$ vite build
vite v2.9.12 building for production...
✓ 266 modules transformed.
dist/assets/react.35ef61ed.svg 4.03 KiB
dist/index.html 0.44 KiB
dist/assets/index.b9195027.css 1.37 KiB / gzip: 0.71 KiB
dist/assets/index.ba61e0ad.js 140.52 KiB / gzip: 45.34 KiB

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 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.

[sapphi-red]

related: #8464

[bluwy]

I think the core issue may be the same as #8464. Closing to keep a single discussion going.