Support for vite@6 async plugins

[manuel3108]

Describe the bug

Using @sveltejs/[email protected] and [email protected] makes tsc fail with the following vite.config.ts

import { defineConfig } from 'vitest/config';
import { sveltekit } from '@sveltejs/kit/vite';

export default defineConfig({
    plugins: [sveltekit()],
});

Problem was first reported in sveltejs/cli#341. While a user is adding vitest to his project, we are switching out the imports inside vite.config.ts like this:

// without vitest
import { defineConfig } from 'vite';

// with vitest
import { defineConfig } from "vitest/config";

This is likely caused by vite@6 allowing plugins of type Promise<whatever>. Looks like this change was not backported to config used by vitest

Reproduction

https://stackblitz.com/edit/node-zjetgl?file=vite.config.ts

Wait for npm i to complete. Run npm run check. The issue will appear. IntelliSense also complains

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: 18.20.3 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.2.3 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    vite: ^6.0.0 => 6.0.2 
    vitest: ^2.1.8 => 2.1.8

Used Package Manager

npm

Validations

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• Read the Contributing Guidelines.
• Read the docs.
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• The provided reproduction is a minimal reproducible example of the bug.

[manuel3108]

I was just made aware of that this was reverted as part of https://github.com/vitest-dev/vitest/releases/tag/v2.1.7, but i would still keep this issue open, as i was unable to find any other issue that's referencing vite 6 support.

But please feel free to close.

[niemyjski]

2.1.7 broke npm run check for us:

import { sveltekit } from '@sveltejs/kit/vite';
import Icons from 'unplugin-icons/vite';
import { defineConfig } from 'vitest/config';

const aspNetConfig = getAspNetConfig();

export default defineConfig({
    build: {
        sourcemap: true,
        target: 'esnext'
    },
    plugins: [
        sveltekit(),
        Icons({
            compiler: 'svelte'
        })
    ],

Exceptionless\src\Exceptionless.Web\ClientApp\vite.config.ts:14:9
Error: No overload matches this call.
  The last overload gave the following error.
    Type 'Promise<Plugin<any>[]>' is not assignable to type 'PluginOption'.
      Type 'Promise<Plugin<any>[]>' is not assignable to type 'Promise<false | Plugin<any> | PluginOption[] | null | undefined>'.
        Type 'Plugin<any>[]' is not assignable to type 'false | Plugin<any> | PluginOption[] | null | undefined'.
          Type 'Plugin<any>[]' is not assignable to type 'PluginOption[]'.
            Type 'Plugin<any>' is not assignable to type 'PluginOption'.