fix: make mount options slots compatible with noUncheckedIndexedAccess true (#2713)

It's not necessary to define all slots, pratially defined slots are used
all over the place throughout the tests here and routinely by users.
However, the type for slots in mount options was not partiall and that
caused type errors for people using `noUncheckedIndexedAccess: true`
even though it work fine in runtime. Adding `?` doesn't change anything
for users with `noUncheckedIndexedAccess: false`, it has passed type
checking before and will continue to pass. Type checking will now also
pass for users with partially defined slots using
`noUncheckedIndexedAccess: true`.

Author: Thomaash

src/mount.ts

@@ -24,7 +24,7 @@ export type ComponentMountingOptions<
   P extends ComponentProps<T> = ComponentProps<T>
 > = Omit<MountingOptions<P, ComponentData<T>>, 'slots'> & {
   slots?: {
-    [K in keyof ComponentSlots<T>]: WithArray<
+    [K in keyof ComponentSlots<T>]?: WithArray<
       | ShimSlotReturnType<ComponentSlots<T>[K]>
       | string
       | VNode

test-dts/mount.d-test.ts

@@ -9,7 +9,9 @@ import {
   ref,
   SetupContext,
   Prop,
-  VNodeChild
+  VNodeChild,
+  SlotsType,
+  VNode
 } from 'vue'
 import { Options, Vue } from 'vue-class-component'
 import { mount } from '../src'
@@ -340,3 +342,82 @@ expectError(
     }
   )
 )
+
+// slots
+const SetupComponentWithSlots = defineComponent<
+  {
+    hello: string
+  },
+  {
+    hallo: () => void
+  },
+  string,
+  SlotsType<{
+    foo: () => VNode[]
+    bar: () => VNode[]
+    baz: () => VNode[]
+  }>
+>((): any => {})
+
+// optional slots
+mount(SetupComponentWithSlots, {})
+
+mount(SetupComponentWithSlots, {
+  slots: {}
+})
+
+mount(SetupComponentWithSlots, {
+  slots: {
+    foo: 'foo'
+  }
+})
+
+mount(SetupComponentWithSlots, {
+  slots: {
+    foo: 'foo',
+    bar: 'bar'
+  }
+})
+
+mount(SetupComponentWithSlots, {
+  slots: {
+    foo: 'foo',
+    bar: 'bar',
+    baz: 'baz'
+  }
+})
+
+// extra slots
+mount(SetupComponentWithSlots, {
+  slots: {
+    // @ts-expect-error - This slot doesn't exist in the component and it should be reported.
+    extraSlot: 'nonExistentSlot'
+  }
+})
+
+mount(SetupComponentWithSlots, {
+  slots: {
+    foo: 'foo',
+    // @ts-expect-error - This slot doesn't exist in the component and it should be reported.
+    extraSlot: 'nonExistentSlot'
+  }
+})
+
+mount(SetupComponentWithSlots, {
+  slots: {
+    foo: 'foo',
+    bar: 'bar',
+    // @ts-expect-error - This slot doesn't exist in the component and it should be reported.
+    extraSlot: 'nonExistentSlot'
+  }
+})
+
+mount(SetupComponentWithSlots, {
+  slots: {
+    foo: 'foo',
+    bar: 'bar',
+    baz: 'baz',
+    // @ts-expect-error - This slot doesn't exist in the component and it should be reported.
+    extraSlot: 'nonExistentSlot'
+  }
+})

test-dts/tsconfig.tsd.json

@@ -4,6 +4,7 @@
     "noEmit": false,
     "skipLibCheck": true,
     "experimentalDecorators": true,
+    "noUncheckedIndexedAccess": true,
     "strictNullChecks": false
   },
   "exclude": [