fix: useCSSModule to adapt the change of getCurrentInstance, close #620 (#622)

* fix(useCssModule): adapting the behavior of `useCSSModule` to the change of `getCurrentInstance`. close #620

* chores: add test for `useCssModule`.

Author: Trendymen

src/apis/useCssModule.ts

@@ -12,7 +12,7 @@ export const useCSSModule = (name = '$style'): Record<string, string> => {
     return EMPTY_OBJ
   }
 
-  const mod = (instance as any)[name]
+  const mod = (instance.proxy as any)?.[name]
   if (!mod) {
     __DEV__ &&
       warn(`Current instance does not have CSS module named "${name}".`)

test/apis/useCssModule.spec.js

@@ -0,0 +1,31 @@
+const Vue = require('vue/dist/vue.common.js')
+const { useCSSModule } = require('../../src')
+
+const style = { whateverStyle: 'whateverStyle' }
+
+function injectStyles() {
+  Object.defineProperty(this, '$style', {
+    configurable: true,
+    get: function () {
+      return style
+    },
+  })
+}
+
+describe('api/useCssModule', () => {
+  it('should get the same object', (done) => {
+    const vm = new Vue({
+      beforeCreate() {
+        injectStyles.call(this)
+      },
+      template: '<div>{{style}}</div>',
+      setup() {
+        const style = useCSSModule()
+        return { style }
+      },
+    })
+    vm.$mount()
+    expect(vm.style).toBe(style)
+    done()
+  })
+})