fix(types): Use alternative Omit

Author: davidmatter

packages/dts-test/setupHelpers.test-d.ts

@@ -100,6 +100,31 @@ describe('defineProps w/ union type declaration + withDefaults', () => {
   )
 })
 
+describe('defineProps w/ generic discriminate union + withDefaults', () => {
+  interface B {
+    b?: string
+  }
+  interface S<T> extends B {
+    mode: 'single'
+    v: T
+  }
+  interface M<T> extends B {
+    mode: 'multiple'
+    v: T[]
+  }
+  type Props = S<string> | M<string>
+  const props = withDefaults(defineProps<Props>(), {
+    b: 'b'
+  })
+
+  if (props.mode === 'single') {
+    expectType<string>(props.v)
+  }
+  if (props.mode === 'multiple') {
+    expectType<string[]>(props.v)
+  }
+})
+
 describe('defineProps w/ generic type declaration + withDefaults', <T extends
   number, TA extends {
   a: string

packages/runtime-core/src/apiSetupHelpers.ts

@@ -293,11 +293,16 @@ type InferDefault<P, T> =
   | ((props: P) => T & {})
   | (T extends NativeType ? T : never)
 
+// https://github.com/vuejs/core/issues/9335
+type OmitKeepDiscriminatedUnion<T, K extends keyof any> = T extends any
+  ? Pick<T, Exclude<keyof T, K>>
+  : never
+
 type PropsWithDefaults<
   T,
   Defaults extends InferDefaults<T>,
   BKeys extends keyof T
-> = Omit<T, keyof Defaults> & {
+> = OmitKeepDiscriminatedUnion<T, keyof Defaults> & {
   [K in keyof Defaults]-?: K extends keyof T
     ? Defaults[K] extends undefined
       ? T[K]