docs: splitVendorChunkPlugin doesn't work with rollupOptions.output.manualChunks object syntax

[Ilanaya]

Documentation is

• Missing
• Outdated
• Confusing
• Not sure?

Explain in Detail

According to this comment (and actual build behavior), splitVendorChunkPlugin doesn't work with rollupOptions.output.manualChunks object form:

manualChunks: {
  lodash: ['lodash']
}

I think this should be mentioned in the docs section as it may cause confusion. And, as I can see, there is really no quick way to acquire the information of the incompatibility except finding the mentioned comment.

Your Suggestion for Changes

Current docs string:
...You can continue to use the Split Vendor Chunk strategy by adding the splitVendorChunkPlugin in your config file:

My proposal:
"...You can continue to use the Split Vendor Chunk strategy by adding the splitVendorChunkPlugin in your config file (important, you should use rollupOptions.output.manualChunks function form when enabling this plugin for correct work)"

Would gladly make PR myself if the you agree this should be mentioned in docs in some form

Reproduction

No response

Steps to reproduce

No response

[sapphi-red]

@maIIady
The proposal looks good to me. Maybe adding a warning container is better.
Also it would be nice to output a warning here.

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

Lines 117 to 118 in 471fba2

	// else, leave the object form of manualChunks untouched, as
	// we can't safely replicate rollup handling.