wip: optimize expose

packages/runtime-core/__tests__/apiExpose.spec.ts

@@ -95,4 +95,50 @@ describe('api: expose', () => {
     expect(childRef.value.bar).toBe(2)
     expect(childRef.value.baz).toBeUndefined()
   })
+
+  test('options: empty', () => {
+    const Child = defineComponent({
+      render() {},
+      expose: [],
+      data() {
+        return {
+          foo: 1
+        }
+      }
+    })
+
+    const childRef = ref()
+    const Parent = {
+      setup() {
+        return () => h(Child, { ref: childRef })
+      }
+    }
+    const root = nodeOps.createElement('div')
+    render(h(Parent), root)
+    expect(childRef.value).toBeTruthy()
+    expect('foo' in childRef.value).toBe(false)
+  })
+
+  test('options: empty + setup context', () => {
+    const Child = defineComponent({
+      render() {},
+      expose: [],
+      setup(_, { expose }) {
+        expose({
+          foo: 1
+        })
+      }
+    })
+
+    const childRef = ref()
+    const Parent = {
+      setup() {
+        return () => h(Child, { ref: childRef })
+      }
+    }
+    const root = nodeOps.createElement('div')
+    render(h(Parent), root)
+    expect(childRef.value).toBeTruthy()
+    expect(childRef.value.foo).toBe(1)
+  })
 })

packages/runtime-core/src/componentOptions.ts

@@ -743,11 +743,19 @@ export function applyOptions(
     onUnmounted(unmounted.bind(publicThis))
   }
 
-  if (!asMixin && expose) {
-    const exposed = instance.exposed || (instance.exposed = proxyRefs({}))
-    expose.forEach(key => {
-      exposed[key] = toRef(publicThis, key as any)
-    })
+  if (isArray(expose)) {
+    if (!asMixin) {
+      if (expose.length) {
+        const exposed = instance.exposed || (instance.exposed = proxyRefs({}))
+        expose.forEach(key => {
+          exposed[key] = toRef(publicThis, key as any)
+        })
+      } else if (!instance.exposed) {
+        instance.exposed = EMPTY_OBJ
+      }
+    } else if (__DEV__) {
+      warn(`The \`expose\` option is ignored when used in mixins.`)
+    }
   }
 }