vite build hangs with multiple scss input files when using 'modern-compiler'

[DKhalil]

Describe the bug

Running npm run build hangs when using multiple .scss files as input. Meaning: it builds successfully but then never exits.

Reproduction

https://github.com/DKhalil/scss-bug-repro

Steps to reproduce

Run npm install then npm run build

System Info

System:
    OS: Windows 10 10.0.19045
    CPU: (16) x64 11th Gen Intel(R) Core(TM) i7-11850H @ 2.50GHz
    Memory: 37.86 GB / 63.71 GB
  Binaries:
    Node: 20.10.0 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.19 - C:\Program Files\nodejs\yarn.CMD
    npm: 10.8.3 - C:\Program Files\nodejs\npm.CMD
    pnpm: 9.10.0 - C:\Program Files\nodejs\pnpm.CMD
    bun: 1.1.0 - ~\.bun\bin\bun.EXE
  Browsers:
    Edge: Chromium (127.0.2651.74)
  npmPackages:
    vite: ^5.4.1 => 5.4.6

Used Package Manager

npm

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 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.

[hi-ogawa]

It looks like sass.initAsyncCompiler is happening twice since optional assignment awaits promise.

vite/packages/vite/src/node/plugins/css.ts

Line 2361 in 53aba77

compiler ??= await sass.initAsyncCompiler()