withDefaults: object unions no longer get merged (fix #10594)

[th1m0]

Before:

withDefaults(
  defineProps<
    {
      def: string
    } & (
      | {
          type: 'hello'
          results: string
        }
      | {
          type: 'world'
          results: number
        }
    )
  >(),
  {
    def: 'default value!',
  }
)

withDefaults would merge the union type to this:

type returnType = {
    readonly type: "hello" | "world";
    readonly results: string | number;
    readonly def: string;
}

This is what should be expected:

type returnType = {
    readonly def: string;
    readonly type: 'hello';
    readonly results: string;
} | {
    readonly def: string;
    readonly type: 'world';
    readonly results: number;
}

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	90.6 kB	34.4 kB	31.1 kB
vue.global.prod.js	148 kB	53.7 kB	48 kB

Usages

Name	Size	Gzip	Brotli
createApp	50.8 kB	19.8 kB	18.1 kB
createSSRApp	54.1 kB	21.2 kB	19.3 kB
defineCustomElement	53.1 kB	20.6 kB	18.8 kB
overall	64.4 kB	24.9 kB	22.6 kB