Make <script setup> support src

[CarterLi]

Due to the difference in module execution semantics, code inside <script setup> relies on the context of an SFC. When moved into external .js or .ts files, it may lead to confusion for both developers and tools. Therefore, <script setup> cannot be used with the src attribute.

If we name the script MyComponent.vue.ts it won't confuse developers

if we explicitly write import { defineProps, defineEmits, defineExpose } from 'vue' it won't confuse tools ( at least for IDEs )

I like to move my business logic code into a seperate file and I don't want to make my template file toooooo long. Please consider it twice.

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Moved from vuejs/core#5902 (comment)

[drocha87]

I'm wondering if it will be to hard to implement a way to infer the code behind without the need to have a <script setup src="..."/> (if it have the same name but ends with .ts for example login.vue and login.vue.ts). This is how it works in Blazor for example.

And now that vscode has Explorer file nesting it's even better.