🐛 Astro components report props as unused even with ignoreExportsUsedInFile enabled

[JoshuaKGoldberg]

Prerequisites

• I'm using the latest version
• I've read the relevant documentation
• I've searched for existing issues
• I've checked the list of known issues
• I've read the issue reproduction guide

Reproduction url

https://github.com/JoshuaKGoldberg/repros/tree/astro-knip-ignoreExportsUsedInFile

Reproduction access

• I've made sure the reproduction is publicly accessible

Description of the issue

ignoreExportsUsedInFile should make it so that all interfaces & props that are exported from a file, but also used in that file, are allowed. This works well for UI/site frameworks that allow explicitly defining components with their prop types. For example, in React, export function MyComponent({...}: MyComponentProps { / export const MyComponent: React.FC<MyComponentProps> = ... are fine.

In Astro components, however, the usage of props is implicit. Defining a shape like interface Props { ... } in a .astro file is how to indicate that file's Astro.props is that shape. But because the name Props isn't explicitly typed out in the file, Knip sees it as unused even if ignoreExportsUsedInFile is enabled.

---
export interface Props {
  happy?: boolean;
}

// Astro.props is now type Props
---

<main>
  <h1>
    {Astro.props.happy ? "Hooray!" : "Good."}
  </h1>
</main>

Proposal: can this be treated as a bug to be fixed?

Originally seen in: https://github.com/flint-fyi/flint/pull/2439/changes#r2937717265

[webpro]

Two questions:

• Why is Props exported in the first place?
• Would the real Astro compiler result change things?

[JoshuaKGoldberg]

Why is Props exported in the first place?

Speaking just for myself, it's similar to the reasoning in #127 (comment). I like standardizing that if there's a component defined using the in-use UI framework & exported, its props shape should be exported as well. I find it helps in standardizing code and treating them as reusable/shareable components by default.

Would the real Astro compiler result change things?

I don't follow, what do you mean?

[webpro]

• With ignoreExportsUsedInFile relying on in-file reference, that makes sense.
• Knip does not have an actual compiler, it's basically just regexes to grab import statements. I'm trying to assess what could or should be handled by Knip vs using the actual Astro compiler to create TypeScript for Knip to parse.