fix(v-model): add value to $attrs if not defined in props (#9331)

fix #9330

Author: lbogdan

src/core/vdom/create-component.js

@@ -250,7 +250,8 @@ function mergeHook (f1: any, f2: any): Function {
 function transformModel (options, data: any) {
   const prop = (options.model && options.model.prop) || 'value'
   const event = (options.model && options.model.event) || 'input'
-  ;(data.props || (data.props = {}))[prop] = data.model.value
+  const addTo = (options.props && prop in options.props) ? 'props' : 'attrs'
+  ;(data[addTo] || (data[addTo] = {}))[prop] = data.model.value
   const on = data.on || (data.on = {})
   const existing = on[event]
   const callback = data.model.callback

test/unit/features/directives/model-component.spec.js

@@ -204,4 +204,30 @@ describe('Directive v-model component', () => {
     expect(triggerCount).toBe(1)
     document.body.removeChild(vm.$el)
   })
+
+  // #9330
+  it('should add value to $attrs if not defined in props', () => {
+    const TestComponent = {
+      inheritAttrs: false,
+      render (h) {
+        return h('div', this.$attrs.value)
+      }
+    }
+
+    const vm = new Vue({
+      components: {
+        TestComponent
+      },
+      template: `
+        <div>
+          <test-component v-model="val"/>
+        </div>
+      `,
+      data: {
+        val: 'foo'
+      }
+    }).$mount()
+
+    expect(vm.$el.innerHTML).toBe('<div>foo</div>');
+  })
 })