prop with default value is still required

[thomasaull]

Vue - Official extension or vue-tsc version

3.2.2

VSCode version

1.104.3

Vue version

3.5.26

TypeScript version

5.9.3

System Info

System:
  OS: Linux 6.18 Fedora Linux 43.20260114.0 (Silverblue)
  CPU: (16) x64 AMD Ryzen 7 9800X3D 8-Core Processor
  Memory: 31.68 GB / 60.47 GB
  Container: Yes
  Shell: 5.9 - /usr/bin/zsh
Binaries:
  Node: 22.16.0 - /var/home/thomasaull/.nvm/versions/node/v22.16.0/bin/node
  npm: 10.9.2 - /var/home/thomasaull/.nvm/versions/node/v22.16.0/bin/npm
  pnpm: 10.17.1 - /var/home/thomasaull/.nvm/versions/node/v22.16.0/bin/pnpm

package.json dependencies

"dependencies": {
  "vue": "^3.5.26"
},
"devDependencies": {
  "@tsconfig/node24": "^24.0.3",
  "@types/node": "^24.10.4",
  "@vitejs/plugin-vue": "^6.0.3",
  "@vue/tsconfig": "^0.8.1",
  "npm-run-all2": "^8.0.4",
  "typescript": "~5.9.3",
  "vite": "^7.3.0",
  "vite-plugin-vue-devtools": "^8.0.5",
  "vue-tsc": "^3.2.2"
},

Steps to reproduce

Child Component

<template>
  <slot />
</template>

<script setup lang="ts">
interface Props {
  variant: 'primary' | 'secondary'
}

const props = withDefaults(defineProps<Props>(), {
  variant: 'primary',
})
</script>

Parent Component:

<script lang="ts" setup>
import Child from './Child.vue'
</script>

<template>
  <Child />
</template>

VS Code shows a type error:

What is expected?

Even though the variant is technically required in the Props interface, since there is a default value, vue treats the prop as not required. The types do not reflect this.

I also did see a change in this behaviour in vue-component-meta, in v2.x there is this line where a prop with a default value is marked as not required:

if (prop.default !== undefined) {
	prop.required = false; // props with default are always optional
}

This apparently changed in v3.x

What is actually happening?

• Type of prop with default value is still required
• vue-component-meta v3.x marks prop with default value as required

Link to minimal reproduction

No response

Any additional comments?

No response