fix(vm): ensure custom properties can be set and read

src/__tests__/lifecylce.spec.ts

@@ -4,7 +4,7 @@ import { defineMixin } from '../defineMixin'
 import { wrapComposable } from './helpers'
 
 describe('Lifecycle hooks', async () => {
-  test('normal lifecycle hooks are called with proper `this`', async () => {
+  test('are called with proper `this`', async () => {
     const spy = vi.fn()
     function testHandler() {
       // @ts-expect-error - doesn't like this for some reason
@@ -44,4 +44,28 @@ describe('Lifecycle hooks', async () => {
 
     expect(spy).toHaveBeenCalledTimes(8)
   })
+
+  test('can read and set custom properties on `this`', async () => {
+    const mixin = defineMixin({
+      props: {},
+      beforeCreate() {
+        ;(this as any).custom = 'A'
+      },
+      created() {
+        expect((this as any).custom).toBe('A')
+      },
+    })
+
+    const composable = createComposableFromMixin(mixin)
+
+    const wrapper = wrapComposable(
+      composable,
+      {},
+      {
+        template: `<div/>`,
+      }
+    )
+
+    expect((wrapper.vm as any).custom).toBe('A')
+  })
 })

src/createComposable.ts

@@ -140,7 +140,7 @@ export /* @__PURE__ */ function createComposableFromMixin<
     const reactiveContext = reactive(context)
     const vmContextProxy = createContextProxy(vm, reactiveContext) as VM
 
-    beforeCreate && callHook(beforeCreate, instance, 'bc')
+    beforeCreate && callHook(beforeCreate, instance, vm, 'bc')
 
     // methods
     if (methods) {
@@ -204,7 +204,7 @@ export /* @__PURE__ */ function createComposableFromMixin<
     }
 
     // Lifecycle
-    created && callHook(created, instance, 'c')
+    created && callHook(created, instance, vm, 'c')
     beforeMount && onBeforeMount(beforeMount.bind(vm))
     mounted && onMounted(mounted.bind(vm))
     beforeUpdate && onBeforeUpdate(beforeUpdate.bind(vm))

src/utils.ts

@@ -1,4 +1,8 @@
-import { callWithAsyncErrorHandling, type ComponentInternalInstance } from 'vue'
+import {
+  callWithAsyncErrorHandling,
+  type ComponentInternalInstance,
+  type ComponentPublicInstance,
+} from 'vue'
 
 export const isFunction = (val: unknown): val is Function =>
   typeof val === 'function'
@@ -15,12 +19,11 @@ export const isString = (val: unknown): val is string => typeof val === 'string'
 export function callHook(
   hook: Function,
   instance: ComponentInternalInstance,
+  vm: ComponentPublicInstance,
   type: 'c' | 'bc'
 ) {
   callWithAsyncErrorHandling(
-    isArray(hook)
-      ? hook.map((h) => h.bind(instance.proxy!))
-      : hook.bind(instance.proxy!),
+    isArray(hook) ? hook.map((h) => h.bind(vm)) : hook.bind(vm),
     instance,
     type as any
   )

src/vmContextProxy.ts

@@ -1,18 +1,18 @@
 import type { ComponentPublicInstance } from 'vue'
 
 export /* #__PURE__ */ function createContextProxy(
-  vm: ComponentPublicInstance,
+  _vm: ComponentPublicInstance,
   context: Record<string, any>
 ) {
-  return new Proxy(vm, {
+  return new Proxy(_vm, {
     get(vm, key, receiver) {
       if (key in context) {
         return Reflect.get(context, key, receiver)
       } else {
         return (vm as any)[key]
       }
     },
-    set(m, key, value, receiver) {
+    set(vm, key, value, receiver) {
       if (key in context) {
         return Reflect.set(context, key, value, receiver)
       } else {