[fix] support using arrays for kit.vite.resolve.alias

[bluwy]

Fixes #2319

Thanks to @JeanJPNM for pointing out the additional places to update.

Notes:

1. Maybe we can do the entire config merge as a Vite plugin per this PR's implementation?
2. I can't put packages/kit/test/global.d.ts into packages/kit/test/ambient.d.ts because the latter has export {} in it, making it a TS module.

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[benmccann]

thanks for the fix! it does feel a bit weird to me to do config merging in two different ways with this PR as it is right now. I would lean towards saying we either make the existing SvelteKit config merging work with regexes or do it with a Vite plugin for the whole Vite config blob (not sure if it'd be the same plugin or not, but I was also planning on adding a Vite plugin in #2232 to provide the SvelteKit middleware to the Vite server after vitejs/vite#4640 is merged)

[dominikg]

i'm in favor of using vite plugins to provide additional config, note that you cannot add vite-plugin-svelte via a config hook though (plugins are final before the hooks are called). But everything else can be done via one or multiple sveltekit:config plugins with respective hooks.

[benmccann]

hmm, I wonder if it just makes things more complicated. we'll still need the sveltekit config merging for non-vite stuff. I wonder if it wouldn't just be simpler to fix the sveltekit config merging to handle regexes instead. it already handles functions, so shouldn't be much different from that

[JeanJPNM]

The problem isn't because of the regexes, is because the alias option had an array as a value, wich cannot be merged with an object.

Here is how it should be:

kit/packages/kit/src/core/dev/index.js

Lines 121 to 136 in bf3efd1

	resolve: {
	alias: Array.isArray(alias)
	? [
	{
	find: '$app',
	replacement: path.resolve(`${this.dir}/runtime/app`)
	},
	{
	find: '$lib',
	replacement: this.config.kit.files.lib
	}
	]
	: {
	$app: path.resolve(`${this.dir}/runtime/app`),
	$lib: this.config.kit.files.lib
	}

But this is a lot more verbose.

[JeanJPNM]

I think we should create a plugins and make plugins for general config, dev and build, to avoid this kind of code duplication.

[JeanJPNM]

The options I see are:

• Hard coded replace
• Anonymous plugins
• Named plugins
• Function specifically made to merge aliases

[benmccann]

ah, thanks for clarifying. it looks like it was handled correctly in dev, but not in build 😝

I see that plugins.svelte.emitCss is also handled differently between the two and I have no idea why - that also looks like it might be broken in some way

[bluwy]

Looking back now, I think adjusting the deep_merge to take into account of of resolve.alias would be cleaner. The extra plugin do seem off, but I think it's the safer choice in the long run if we do let Vite handle the config merging for us. resolveConfig might be handy too. I can look into that soon, but for now I'll refactor the code to not use a Vite plugin.

Update: There's also the mergeConfig function exported from vite.

[bluwy]

Updated to have deep_merge take into account of resolve.alias, instead of using Vite plugins.

[benmccann]

awesome! this looks great! thanks so much 😄