`.less` files as input errors after 7.1.3

[Sysix]

Describe the bug

Wanted to reproduce a Less Bug with lightningcss, but I failed to create a usable reproduction.
When running in vite@7.1.2 everything works fine, with @vite.7.1.3 I got the error:

UnhandledPromiseRejection: This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason "ReferenceError: 𝐢𝐦𝐩𝐨𝐫𝐭 is not defined".

Simple vite config:

import { defineConfig } from 'vite';

export default defineConfig({
  build: {
    cssMinify: 'esbuild',
    rollupOptions: {
      input: ['src/main.js', 'src/test.less'],
    },
  },
});

Reproduction

https://stackblitz.com/edit/vitejs-vite-t2ppd7ej?file=vite.config.mjs

Steps to reproduce

Run npm install followed by npm run build.
With npm install vite@7.1.2 and npm run build, no error happens.

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 20.19.1 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.8.2 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    vite: ^7.1.3 => 7.1.3

Used Package Manager

npm

Logs

Click to expand!

npm run build --debug

> vite-starter@0.0.0 build
> vite build

vite v7.1.3 building for production...
transforming (1) src/main.jsUnhandledPromiseRejection: This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason "ReferenceError: 𝐢𝐦𝐩𝐨𝐫𝐭 is not defined".
    at _0x545e32 (https://vitejsvitet2ppd7ej-o4tq.w-corp-staticblitz.com/blitz.96435430.js:31:22523)
    at UnhandledPromiseRejection (node:internal/process/promises:193:1037)
    at throwUnhandledRejectionsMode (node:internal/process/promises:193:4316)
    at processPromiseRejections (node:internal/process/promises:193:5015)
    at processTicksAndRejections (node:internal/process/task_queues:196:1218)
    at <anonymous> (https://vitejsvitet2ppd7ej-o4tq.w-corp-staticblitz.com/blitz.96435430.js:31:552231) {
  code: 'ERR_UNHANDLED_REJECTION'
}

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]

Does this error happen locally? I did reproduce on stackblitz, but didn't reproduce on both Windows and WSL.

Related PR: #20641

[Sysix]

The error appears only on stackblitz. Tested locally in with the latest version.