PropType with Interface with all optional properties leads to unknown type

[Cherry]

Vue version

3.4.31

Link to minimal reproduction

https://play.vuejs.org/#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

Steps to reproduce

• Open reproduction
• Open Comp.vue file
• See line 26 to find the type for item is unknown
• But on line 27, see the type for otherItem is set to OtherItem

What is expected?

The type for item on line 26 should be the Item interface defined on line 5.

What is actually happening?

The type for item is returning unknown.

System Info

System:
    OS: Windows 11 10.0.22631
    CPU: (16) x64 AMD Ryzen 7 3700X 8-Core Processor
    Memory: 10.01 GB / 31.91 GB
  Binaries:
    Node: 20.15.0 - C:\Program Files\nodejs\node.EXE
    npm: 10.8.1 - C:\Program Files\nodejs\npm.CMD
    pnpm: 9.1.2 - C:\Program Files\nodejs\pnpm.CMD
  Browsers:
    Edge: Chromium (126.0.2592.81)
    Internet Explorer: 11.0.22621.3527
  npmPackages:
    vue: 3.4.31 => 3.4.31

Any additional comments?

It seems that whenever an Interface/type contains only optional properties, the type that's inferred is always unknown.

[jh-leong]

as a workaround use defineProps<Props>(): playground

[jh-leong]

FYI: This doesn't seem to be a Vue type issue, ref TypeScript playground

[yyx990803]

This seems to only happen in the playground, maybe due to outdated Volar used?

I can't reproduce this locally in VSCode either.

[Cherry]

That's very interesting, thank you for taking a look.

With a fresh npm create vue@latest project, I'm also unable to reproduce this. But in a project at work, I still am able to when using vue@3.4.31, @vue/language-core@2.0.26 and VSCode extension vue.volar at v2.0.26 within VSCode, all latest versions.

I didn't think to test this way since I was able to repro quickly in the playground. Let me see if I can do some more digging and get back to you.

[yyx990803]

Closing as a duplicate of #11733 - neither can be reproduced on my end so let's keep only one open.

[danielroe]

Here's a minimal reproduction (just vue + vue-tsc) showing the issue:

https://stackblitz.com/edit/stackblitz-starters-zu6gov

To be clear, this issue is only reproducible with strict: false. It's not reproducible on the SFC playground for some reason, even when updating tsconfig.json.