Migrate: comments on props are either detached or deleted

[paoloricciuti]

Describe the bug

A common pattern if you are building a large application with svelte is to document you props with JSDoc or at least with comment.

Currently the migration script falls a bit short for this very common situation:

<script>
	/**
	 * My wonderful comment
	 * @type {string}
	 */
	export let comment;

	/**
	 * My wonderful other comment
	 * @type {number}
	 */	
	export let another_comment;
</script>

is converted into

<script>
	

		
	/** @type {{comment: string, another_comment: number}} */
	let { comment, another_comment } = $props();
</script>

And just like that all time spent into writing documentation for your props is trashed.

The situation is a bit worst if the comment is a line comment

<script>
	// pay attention to this
	export let comment;

	let totally_innocuous_state = 0;

	/**
	 * My wonderful other comment
	 */	
	export let another_comment;
</script>

is converted into this

<script>
	// pay attention to this

	let totally_innocuous_state = 0;

		
	/** @type {{comment: any, another_comment: any}} */
	let { comment, another_comment } = $props();
</script>

i thought of moving all the comments related to props above the props but that could be just confusing. But what if we use another approach.

This also works in JSDoc

<script>

	 /**
	 * @typedef {Object} Props
	 * @property {string} comment - My wonderful comment
	 * @property {string} another_comment - My wonderful other comment
	 */
	
	/** @type {Props} */
	let { comment, another_comment } = $props();
</script>

and we could even move the lines comments there (even tho it's not exactly right i would be less pissed to have a line comment in the JSDoc that have it lingering around the file)

Do you think is worth?

Reproduction

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System Info

repl

Severity

annoyance

[benmccann]

Yes, I agree with making a typedef and moving the comments there. Current situation seems quite bad