`custom_element_props_identifier` warnings should not be triggered for internally imported components

[JetLua]

<!-- A.svelte -->
<svelte:options customElement={{
  tag: 'a-btn',
  props: {
    name: {type: 'String'},
  }
}}/>

<script lang="ts">
  import B from './B.svelte'
  const props: {name: string} = $props()

</script>

<B name={props.name}/>

<!-- B.svelte -->

<script lang="ts">
  const props: {name: string} = $props()
</script>

<button>{props.name}</button>

Perhaps a trigger warning shouldn't be issued for file B.svelte.

https://stackblitz.com/edit/vitejs-vite-1tpdpcqa?file=src%2FB.svelte

Originally posted by @JetLua in #16003 (comment)

[paoloricciuti]

Currently the svelte runtime is not using the type information to infer which properties to expose and tbf i don't think we should either as it would be very weird if moving the type to it's own declaration would reintroduce the warning.

So personally I would close this but let's wait what others have to say.

[Ocean-OS]

If we were to migrate from acorn-typescript to a parser that analyzes type information across multiple files, we probably could fix that
That might have additional benefits (eg type-informed optimization), but I'm not sure what parsers there are that fit this criteria (other than the typescript package)

[paoloricciuti]

Find a replacement would be difficult but also cross file compilation would be difficult...not impossible but difficult for sure

[Ocean-OS]

Yeah, and at that point it'd seem odd not to implement whole app optimization (#1102) if compilation spanned across multiple files
There's a lot of potential work here, but there's also a lot of potential benefit

[Rich-Harris]

I'm going to close this as wontfix — it doesn't matter that you're not using B.svelte as a custom element, the fact is you're still compiling it as a custom element (i.e. anyone could import B from './B.svelte and register B.element), and thus the warning is valid. The solution is to not do that, i.e. ensure that only components designed to be used as custom elements are compiled as such.

Since you're using vite-plugin-svelte you can use dynamicCompileOptions for this