refactor: move plugin options to "vitePlugin" in svelte.config.js

[dominikg]

To avoid problems with future name clashes we introduce vitePlugin namespace in svelte.config.js.

svelte options that are of global interest, eg compilerOptions, preprocess and extensions remain in the config root.

All other options mentioned in https://github.com/sveltejs/vite-plugin-svelte/blob/main/docs/config.md#plugin-options are moved.

Additional validation/errors have been introduced to avoid invalid options and inform the user.

[ghostdevv]

Are you planning on supporting both for a while? there have been so many breaking changes in svelte projects recently it might be nice to have a break 😅

[dominikg]

No, this is breaking. But it should be the last one before vite-plugin-svelte 1.0.0

[bluwy]

Some spacing nits, but the src looks good to me. Maybe we also want to export a new type for vitePlugin? Currently we have Options that's for passing the the plugin directly.

[ganigeorgiev]

@bluwy, @dominikg Is this change available in the recent v1.0.1 release?

When I wrap my options under vitePlugin as per the release note, like this:

// vite.config.js
export default defineConfig({
    plugins: [
        svelte({
            vitePlugin: {
                experimental: {
                    useVitePreprocess: true,
                },
            },
        }),
    ],
    ...
});

I'm seeing the following warning in the console:

[vite-plugin-svelte] invalid plugin options "vitePlugin" in inline config
{ vitePlugin: { experimental: { useVitePreprocess: true } } }

[dominikg]

inline in vite config you do not wrap them. Only in svelte.config.js

[ganigeorgiev]

Ah, sorry. Yes, I've just read https://github.com/sveltejs/vite-plugin-svelte/blob/main/docs/config.md#experimental-options where is mentioned that this change is only for svelte.config.js.

This is kind of confusing to be honest and would be better to be consistent. Furthermore the example at the top of the page has this:

// vite.config.js
export default defineConfig({
  plugins: [
    svelte({
      configFile: false
      // your svelte config here
    })
  ]
});

where I thought because of // your svelte config here it should support the same props.

[dominikg]

Imho vitePlugin would be redundant inside vite.config.js inline options. It is used in svelte.config.js because that file isn't exclusive for vite-plugin-svelte.
The inline options in vite.config.js on the other hand are ours to define and use.

[ganigeorgiev]

@dominikg Fair enough, I agree. It is just a little confusing and some people may stumble on this, but there is also validation for the config, so I think we are OK.