fix(runtime-core/emits): merge emits options from mixins/extends

fix #1562

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

@@ -143,12 +143,47 @@ describe('component: emit', () => {
     expect(`event validation failed for event "foo"`).toHaveBeenWarned()
   })
 
+  test('merging from mixins', () => {
+    const mixin = {
+      emits: {
+        foo: (arg: number) => arg > 0
+      }
+    }
+    const Foo = defineComponent({
+      mixins: [mixin],
+      render() {},
+      created() {
+        this.$emit('foo', -1)
+      }
+    })
+    render(h(Foo), nodeOps.createElement('div'))
+    expect(`event validation failed for event "foo"`).toHaveBeenWarned()
+  })
+
   test('isEmitListener', () => {
-    expect(isEmitListener(['click'], 'onClick')).toBe(true)
-    expect(isEmitListener(['click'], 'onclick')).toBe(false)
-    expect(isEmitListener({ click: null }, 'onClick')).toBe(true)
-    expect(isEmitListener({ click: null }, 'onclick')).toBe(false)
-    expect(isEmitListener(['click'], 'onBlick')).toBe(false)
-    expect(isEmitListener({ click: null }, 'onBlick')).toBe(false)
+    const def1 = { emits: ['click'] }
+    expect(isEmitListener(def1, 'onClick')).toBe(true)
+    expect(isEmitListener(def1, 'onclick')).toBe(false)
+    expect(isEmitListener(def1, 'onBlick')).toBe(false)
+
+    const def2 = { emits: { click: null } }
+    expect(isEmitListener(def2, 'onClick')).toBe(true)
+    expect(isEmitListener(def2, 'onclick')).toBe(false)
+    expect(isEmitListener(def2, 'onBlick')).toBe(false)
+
+    const mixin1 = { emits: ['foo'] }
+    const mixin2 = { emits: ['bar'] }
+    const extend = { emits: ['baz'] }
+    const def3 = {
+      emits: { click: null },
+      mixins: [mixin1, mixin2],
+      extends: extend
+    }
+    expect(isEmitListener(def3, 'onClick')).toBe(true)
+    expect(isEmitListener(def3, 'onFoo')).toBe(true)
+    expect(isEmitListener(def3, 'onBar')).toBe(true)
+    expect(isEmitListener(def3, 'onBaz')).toBe(true)
+    expect(isEmitListener(def3, 'onclick')).toBe(false)
+    expect(isEmitListener(def3, 'onBlick')).toBe(false)
   })
 })