fix: allow mocking on script setup components (#1861)

We need to differentiate how the mixin used for mocking updates the isntance,
as Vue v3.2.45 now forbids to update directly a script setup component from a component written with the Options API.

Fixes the error `set' on proxy: trap returned falsish for property`

This comes from the fact that mocks are set via a mixin (Options API) and we run into the more strict behavior of Vue v3.2.45
introduced in vuejs/core@f73925d#diff-ea4d1ddabb7e22e17e80ada458eef70679af4005df2a1a6b73418fec897603ceR404

Author: cexbrayat

src/mount.ts

@@ -33,6 +33,7 @@ import { MountingOptions, Slot } from './types'
 import {
   getComponentsFromStubs,
   getDirectivesFromStubs,
+  hasSetupState,
   isFunctionalComponent,
   isObject,
   isObjectComponent,
@@ -475,15 +476,23 @@ export function mount(
 
   // global mocks mixin
   if (global?.mocks) {
-    const mixin = {
+    const mixin = defineComponent({
       beforeCreate() {
         for (const [k, v] of Object.entries(
           global.mocks as { [key: string]: any }
         )) {
-          ;(this as any)[k] = v
+          // we need to differentiate components that are or not not `script setup`
+          // otherwise we run into a proxy set error
+          // due to https://github.com/vuejs/core/commit/f73925d76a76ee259749b8b48cb68895f539a00f#diff-ea4d1ddabb7e22e17e80ada458eef70679af4005df2a1a6b73418fec897603ceR404
+          // introduced in Vue v3.2.45
+          if (hasSetupState(this as any)) {
+            ;(this as any).$.setupState[k] = v
+          } else {
+            ;(this as any)[k] = v
+          }
         }
       }
-    }
+    })
 
     app.mixin(mixin)
   }

src/utils.ts

@@ -2,6 +2,7 @@ import { GlobalMountOptions, RefSelector, Stub, Stubs } from './types'
 import {
   Component,
   ComponentOptions,
+  ComponentPublicInstance,
   ConcreteComponent,
   Directive,
   FunctionalComponent
@@ -185,3 +186,11 @@ export function getDirectivesFromStubs(
       .map(([key, value]) => [key.substring(1), value])
   ) as Record<string, Directive>
 }
+export function hasSetupState(
+  vm: ComponentPublicInstance
+): vm is ComponentPublicInstance & { setupState: Record<string, unknown> } {
+  return (
+    vm &&
+    (vm.$ as unknown as { devtoolsRawSetupState: any }).devtoolsRawSetupState
+  )
+}

src/vueWrapper.ts

@@ -8,7 +8,7 @@ import {
 import { config } from './config'
 import domEvents from './constants/dom-events'
 import { VueElement, VueNode } from './types'
-import { mergeDeep } from './utils'
+import { hasSetupState, mergeDeep } from './utils'
 import { getRootNodes } from './utils/getRootNodes'
 import { emitted, recordEvent, removeEventHistory } from './emit'
 import BaseWrapper from './baseWrapper'
@@ -107,10 +107,7 @@ export class VueWrapper<
     // This does not work for functional components though (as they have no vm)
     // or for components with a setup that returns a render function (as they have an empty proxy)
     // in both cases, we return `vm` directly instead
-    if (
-      vm &&
-      (vm.$ as unknown as { devtoolsRawSetupState: any }).devtoolsRawSetupState
-    ) {
+    if (hasSetupState(vm)) {
       this.componentVM = createVMProxy<T>(vm, (vm.$ as any).setupState)
     } else {
       this.componentVM = vm

tests/expose.spec.ts

@@ -91,4 +91,23 @@ describe('expose', () => {
     await wrapper.find('button').trigger('click')
     expect(wrapper.html()).toContain('3')
   })
+
+  it('should not throw when mocking', async () => {
+    const spiedIncrement = vi.fn()
+    const wrapper = mount(ScriptSetup, {
+      global: {
+        mocks: {
+          count: -1,
+          inc: spiedIncrement
+        }
+      }
+    })
+    expect(wrapper.html()).toContain('-1')
+
+    await wrapper.find('button').trigger('click')
+    await nextTick()
+
+    expect(spiedIncrement).toHaveBeenCalled()
+    expect(wrapper.html()).toContain('-1')
+  })
 })