Support an async function to provide vite config

[ispyinternet]

fixes #3436

[changeset-bot]

🦋 Changeset detected

Latest commit: 50152f8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sveltejs/kit	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[netlify]

✔️ Deploy Preview for kit-demo ready!

🔨 Explore the source changes: 50152f8

🔍 Inspect the deploy log: https://app.netlify.com/sites/kit-demo/deploys/61f93da90ca2ca00083e220a

😎 Browse the preview: https://deploy-preview-3565--kit-demo.netlify.app

[ispyinternet]

Don't think it breaks anything 🤷‍♂️ any help to get working would be appreciated.

[benmccann]

You need to run pnpm format

[dominikg]

It would be good to update the docs and config type to show that an async function can be used too.

Please also add a changeset.

sidenote:
Got confused at first because your PR never handles the vite config as object case, but it looks like the validator turns an object into ()=>object. I didn't expect that but makes sense to have it in a single place

[Rich-Harris]

This seems like a harmless change so I'm 👍 , though I'm curious what the use case is? You can use top-level await in your svelte.config.js, so it seems like anything enabled by this change should already be possible

[ispyinternet]

Ah can I? I tried to export an async function that returned a svelte.config.js object but that didn't work.

Basically I have async config that I inject into the application code (typescript files not .svelte so I can't use svelte preprocess). I'm using rollup/plugin-replace via vite 🤷

[Rich-Harris]

yep, you can do this:

export default {
  kit: {
    vite: {
      plugins: [
        replace(await load_replacements());
      ]
    }
  }
};

given that, do we still need this change?

[ispyinternet]

Sorry no reply @Rich-Harris tied up elsewhere!