refactor: throw error for functional components in props (#460)

Author: eddyerburgh

packages/test-utils/src/wrapper.js

@@ -385,6 +385,9 @@ export default class Wrapper implements BaseWrapper {
    * Returns an Object containing the prop name/value pairs on the element
    */
   props (): { [name: string]: any } {
+    if (this.isFunctionalComponent) {
+      throwError('wrapper.props() cannot be called on a mounted functional component.')
+    }
     if (!this.vm) {
       throwError('wrapper.props() must be called on a Vue instance')
     }

test/specs/wrapper/props.spec.js

@@ -1,6 +1,10 @@
 import { compileToFunctions } from 'vue-template-compiler'
 import ComponentWithProps from '~resources/components/component-with-props.vue'
-import { describeWithShallowAndMount } from '~resources/utils'
+import {
+  describeWithShallowAndMount,
+  itSkipIf,
+  functionalSFCsSupported
+} from '~resources/utils'
 
 describeWithShallowAndMount('props', (mountingMethod) => {
   it('returns true if wrapper has prop', () => {
@@ -32,6 +36,30 @@ describeWithShallowAndMount('props', (mountingMethod) => {
     expect(wrapper.props()).to.eql({ prop1: {}, prop2: 'val2' }) // fail
   })
 
+  itSkipIf(!functionalSFCsSupported(),
+    'works correctly a functional component', () => {
+      const FunctionalComponent = {
+        render: h => h('div'),
+        functional: true,
+        props: ['prop1']
+      }
+      const TestComponent = {
+        template: '<div><functional-component /></div>',
+        components: { FunctionalComponent }
+      }
+      const prop1 = 'some prop'
+      const wrapper = mountingMethod(TestComponent, {
+        propsData: {
+          prop1
+        }
+      })
+      if (mountingMethod.name === 'mount') {
+        const message = '[vue-test-utils]: wrapper.props() cannot be called on a mounted functional component.'
+        const fn = () => wrapper.find(FunctionalComponent).props()
+        expect(fn).to.throw().with.property('message', message)
+      }
+    })
+
   it('throws an error if called on a non vm wrapper', () => {
     const compiled = compileToFunctions('<div><p /></div>')
     const p = mountingMethod(compiled).findAll('p').at(0)