fix: expose props on vm for script setup components

Fixes #1863

It turns out `vm` is not enough, and we need to proxy to `vm.$.ctx` which contains the props as well.

src/vueWrapper.ts

@@ -35,7 +35,9 @@ function createVMProxy<T extends ComponentPublicInstance>(
       if (key in setupState) {
         return Reflect.get(setupState, key, receiver)
       } else {
-        return (vm as any)[key]
+        // vm.$.ctx is the internal context of the vm
+        // with all variables, methods and props
+        return (vm as any).$.ctx[key]
       }
     },
     set(vm, key, value, receiver) {

tests/components/ScriptSetupWithProps.vue

@@ -0,0 +1,13 @@
+<script setup lang="ts">
+import { ref } from 'vue';
+
+const props = defineProps<{ count: number }>()
+const internalCount = ref(props.count);
+const inc = () => {
+  internalCount.value++
+}
+</script>
+
+<template>
+  <button @click="inc">{{ internalCount }}</button>
+</template>

tests/expose.spec.ts

@@ -6,6 +6,7 @@ import DefineExpose from './components/DefineExpose.vue'
 import DefineExposeWithRenderFunction from './components/DefineExposeWithRenderFunction.vue'
 import ScriptSetupExpose from './components/ScriptSetup_Expose.vue'
 import ScriptSetup from './components/ScriptSetup.vue'
+import ScriptSetupWithProps from './components/ScriptSetupWithProps.vue'
 
 describe('expose', () => {
   it('access vm on simple components', async () => {
@@ -76,4 +77,18 @@ describe('expose', () => {
     expect(spiedIncrement).toHaveBeenCalled()
     expect(wrapper.html()).toContain('0')
   })
+
+  it('access props on vm with <script setup>', async () => {
+    const wrapper = mount(ScriptSetupWithProps, {
+      props: {
+        count: 2
+      }
+    })
+    // make sure that props are accessible on wrapper.vm
+    expect(wrapper.vm.count).toBe(2)
+    expect(wrapper.html()).toContain('2')
+
+    await wrapper.find('button').trigger('click')
+    expect(wrapper.html()).toContain('3')
+  })
 })