TypeScript is not useful with fallback

[karchung0930]

I believe Svelte transpiles the TypeScript code on the fly by npm run dev.
If a property is required in TypeScript but is missing in actual execution, the app will simply crash.

Consider the below example with TypeScript and user doesn't provide the property which is required:

<!-- Child.svelte -->
<script lang="ts">
    let { text }: { text: string } = $props();
</script>

<p>{text}</p>

<!-- Parent.svelte -->
<script lang="ts">
    import Child from '$lib/components/Child.svelte';
</script>

<Child />

The core idea of TypeScript is static type checking—catching errors before runtime. Imagine if:

• Other developers ignore type warnings
• He doesn't install the extension where he cannot see the errors reported by Typescripts or his editor just not showing ( not supported TypeScript feature ) those errors at all

The result is actually more or less the same without TypeScript.

Unless I explicitly make a fallback for the required property:

<!-- Child.svelte -->
<script>
    let { text = 'default' } = $props();
</script>

<p>{text}</p>

But then again, why still need TypeScript in this case since already provided fallback. The difference is that we need to manually compile the TypeScript and it will fails for the above case for regular TypeScript application. But with Svelte and other frameworks, this is not the case.

My question is:

• Do I just ignore the situations mentioned aboved and just let people debug when the app is crashed?
• Or I provide the fallback with TypeScript but then I think it goes against the concept of TypeScript and increase the workload of TypeScript developer.

This might not a question directly related to Svelte but I'd like to know the thoughts of the developers from the ecosystem of Svelte and other professionals.

[brunnerh]

My personal view on this is that if people don't use something correctly while having all the tools to do otherwise, that is their problem.

The types, svelte-check and the extensions are there to help them prevent mistakes, if people choose to not make use of those and run into trouble because of it, that is simply the consequence of their own actions.

My one criticism towards Svelte would be that type checking does not happen by default and you need to separately run svelte-check. I think ideally that would be integrated directly into the compilation step.