feat(stubs): Allow to stub directives

* this adds stubbing directives functionality to @vue/test-utils

docs/guide/advanced/stubs-shallow-mount.md

@@ -1,6 +1,6 @@
 # Stubs and Shallow Mount
 
-Vue Test Utils provides some advanced features for _stubbing_ components. A _stub_ is where you replace an existing implementation of a custom component with a dummy component that doesn't do anything at all, which can simplify an otherwise complex test. Let's see an example.
+Vue Test Utils provides some advanced features for _stubbing_ components and directives. A _stub_ is where you replace an existing implementation of a custom component or directive with a dummy one that doesn't do anything at all, which can simplify an otherwise complex test. Let's see an example.
 
 ## Stubbing a single child component
 
@@ -238,6 +238,78 @@ test('stubs async component with resolving', async () => {
 })
 ```
 
+## Stubbing a directive
+
+Sometimes directives do quite complex things, like perform a lot of DOM manipulation which might result in errors in your tests (due to JSDOM not resembling entire DOM behavior). A common example is tooltip directives from various libraries, which usually rely heavily on measuring DOM nodes position/sizes.
+
+In this example, we have another `<App>` that renders a message with tooltip
+
+```js
+// tooltip directive declared somewhere, named `Tooltip`
+
+const App = {
+  directives: {
+    Tooltip
+  },
+  template: '<h1 v-tooltip title="Welcome tooltip">Welcome to Vue.js 3</h1>'
+}
+```
+
+We do not want `Tooltip` directive code to be executed in this test, we just want to assert the message is rendered. In this case, we could use the `stubs`, which appears in the `global` mounting option passing `vTooltip`.
+
+```js
+test('stubs component with custom template', () => {
+  const wrapper = mount(App, {
+    global: {
+      stubs: {
+        vTooltip: true
+      }
+    }
+  })
+
+  console.log(wrapper.html())
+  // <h1>Welcome to Vue.js 3</h1><span></span>
+
+  expect(wrapper.html()).toContain('Welcome to Vue.js 3')
+})
+```
+
+::: tip
+Usage of `vCustomDirective` naming scheme to differentiate between components and directives is inspired by [same approach](https://vuejs.org/api/sfc-script-setup.html#using-custom-directives) used in `<script setup>`
+:::
+
+Sometimes, we need a part of directive functionality (usually because some code relies on it). Let's assume our directive adds `with-tooltip` CSS class when executed and this is important behavior for our code. In this case we can swap `true` with our mock directive implementation
+
+```js
+test('stubs component with custom template', () => {
+  const wrapper = mount(App, {
+    global: {
+      stubs: {
+        vTooltip: {
+          beforeMount(el: Element) {
+            console.log('directive called')
+            el.classList.add('with-tooltip')
+          }
+        }
+      }
+    }
+  })
+
+  // 'directive called' logged to console
+
+  console.log(wrapper.html())
+  // <h1>Welcome to Vue.js 3</h1><span></span>
+
+  expect(wrapper.classes('with-tooltip')).toBe(true)
+})
+```
+
+We've just swapped our directive implementation with own one!
+
+::: warning
+Stubbing directives won't work on functional components due to lack of directive name inside of [withDirectives](https://vuejs.org/api/render-function.html#withdirectives) function. Consider mocking directive module via your testing framework if you need to mock directive used in functional component
+:::
+
 ## Default Slots and `shallow`
 
 Since `shallow` stubs out all the content of a components, any `<slot>` won't get rendered when using `shallow`. While this is not a problem in most cases, there are some scenarios where this isn't ideal.
@@ -314,6 +386,6 @@ So regardless of which mounting method you choose, we suggest keeping these guid
 
 ## Conclusion
 
-- use `global.stubs` to replace a component with a dummy one to simplify your tests
+- use `global.stubs` to replace a component or directive with a dummy one to simplify your tests
 - use `shallow: true` (or `shallowMount`) to stub out all child components
 - use `config.renderStubDefaultSlot` to render the default `<slot>` for a stubbed component

src/mount.ts

@@ -30,6 +30,8 @@ import {
 
 import { MountingOptions, Slot } from './types'
 import {
+  getComponentsFromStubs,
+  getDirectivesFromStubs,
   isFunctionalComponent,
   isObject,
   isObjectComponent,
@@ -41,15 +43,16 @@ import { attachEmitListener } from './emit'
 import { createVNodeTransformer } from './vnodeTransformers/util'
 import {
   createStubComponentsTransformer,
-  addToDoNotStubComponents,
-  registerStub
+  addToDoNotStubComponents
 } from './vnodeTransformers/stubComponentsTransformer'
+import { createStubDirectivesTransformer } from './vnodeTransformers/stubDirectivesTransformer'
 import {
   isLegacyFunctionalComponent,
   unwrapLegacyVueExtendComponent
 } from './utils/vueCompatSupport'
 import { trackInstance } from './utils/autoUnmount'
 import { createVueWrapper } from './wrapperFactory'
+import { registerStub } from './stubs'
 
 // NOTE this should come from `vue`
 const MOUNT_OPTIONS: Array<keyof MountingOptions<any>> = [
@@ -338,7 +341,10 @@ export function mount(
   }
 
   addToDoNotStubComponents(component)
+  // We've just replaced our component with it's copy
+  // Let's register it as a stub so user can find it
   registerStub({ source: originalComponent, stub: component })
+
   const el = document.createElement('div')
 
   if (options?.attachTo) {
@@ -532,9 +538,12 @@ export function mount(
     createVNodeTransformer({
       transformers: [
         createStubComponentsTransformer({
-          stubs: global.stubs,
+          stubs: getComponentsFromStubs(global.stubs),
           shallow: options?.shallow,
           renderStubDefaultSlot: global.renderStubDefaultSlot
+        }),
+        createStubDirectivesTransformer({
+          directives: getDirectivesFromStubs(global.stubs)
         })
       ]
     })
@@ -551,7 +560,7 @@ export function mount(
   // ref: https://github.com/vuejs/test-utils/issues/249
   // ref: https://github.com/vuejs/test-utils/issues/425
   if (global?.stubs) {
-    for (const name of Object.keys(global.stubs)) {
+    for (const name of Object.keys(getComponentsFromStubs(global.stubs))) {
       if (!app.component(name)) {
         app.component(name, { name })
       }

src/stubs.ts

@@ -0,0 +1,32 @@
+import { Component } from 'vue'
+
+// Stubbing occurs when in vnode transformer we're swapping
+// component vnode type due to stubbing either component
+// or directive on component
+
+// In order to be able to find components we need to track pairs
+// stub --> original component
+
+// Having this as global might feel unsafe at first point
+// One can assume that sharing stub map across mounts might
+// lead to false matches, however our vnode mappers always
+// produce new nodeTypes for each mount even if you're reusing
+// same stub, so we're safe and do not need to pass these stubs
+// for each mount operation
+const stubs: WeakMap<Component, Component> = new WeakMap()
+
+export function registerStub({
+  source,
+  stub
+}: {
+  source: Component
+  stub: Component
+}) {
+  stubs.set(stub, source)
+}
+
+export function getOriginalComponentFromStub(
+  stub: Component
+): Component | undefined {
+  return stubs.get(stub)
+}

src/types.ts

@@ -86,7 +86,7 @@ export interface MountingOptions<Props, Data = {}> {
   shallow?: boolean
 }
 
-export type Stub = boolean | Component
+export type Stub = boolean | Component | Directive
 export type Stubs = Record<string, Stub> | Array<string>
 export type GlobalMountOptions = {
   /**

src/utils.ts

@@ -1,5 +1,11 @@
-import { GlobalMountOptions, RefSelector } from './types'
-import { ComponentOptions, ConcreteComponent, FunctionalComponent } from 'vue'
+import { GlobalMountOptions, RefSelector, Stub, Stubs } from './types'
+import {
+  Component,
+  ComponentOptions,
+  ConcreteComponent,
+  Directive,
+  FunctionalComponent
+} from 'vue'
 import { config } from './config'
 
 function mergeStubs(target: Record<string, any>, source: GlobalMountOptions) {
@@ -137,3 +143,39 @@ export function isRefSelector(
 ): selector is RefSelector {
   return typeof selector === 'object' && 'ref' in selector
 }
+
+export function convertStubsToRecord(stubs: Stubs) {
+  if (Array.isArray(stubs)) {
+    // ['Foo', 'Bar'] => { Foo: true, Bar: true }
+    return stubs.reduce((acc, current) => {
+      acc[current] = true
+      return acc
+    }, {} as Record<string, Stub>)
+  }
+
+  return stubs
+}
+
+const isDirectiveKey = (key: string) => key.match(/^v[A-Z].*/)
+
+export function getComponentsFromStubs(
+  stubs: Stubs
+): Record<string, Component | boolean> {
+  const normalizedStubs = convertStubsToRecord(stubs)
+
+  return Object.fromEntries(
+    Object.entries(normalizedStubs).filter(([key]) => !isDirectiveKey(key))
+  ) as Record<string, Component | boolean>
+}
+
+export function getDirectivesFromStubs(
+  stubs: Stubs
+): Record<string, Directive> {
+  const normalizedStubs = convertStubsToRecord(stubs)
+
+  return Object.fromEntries(
+    Object.entries(normalizedStubs)
+      .filter(([key]) => isDirectiveKey(key))
+      .map(([key, value]) => [key.substring(1), value])
+  ) as Record<string, Directive>
+}

src/utils/find.ts

@@ -5,11 +5,8 @@ import {
   VNodeNormalizedChildren,
   VNodeTypes
 } from 'vue'
+import { getOriginalComponentFromStub } from '../stubs'
 import { FindAllComponentsSelector } from '../types'
-import {
-  getOriginalStubFromSpecializedStub,
-  getOriginalVNodeTypeFromStub
-} from '../vnodeTransformers/stubComponentsTransformer'
 import { isComponent } from '../utils'
 import { matchName } from './matchName'
 import { unwrapLegacyVueExtendComponent } from './vueCompatSupport'
@@ -45,11 +42,15 @@ export function matches(
 
   const nodeTypeCandidates: VNodeTypes[] = [
     nodeType,
-    getOriginalVNodeTypeFromStub(nodeType),
-    getOriginalStubFromSpecializedStub(nodeType)
+    getOriginalComponentFromStub(nodeType)
+    // getOriginalVNodeTypeFromStub(nodeType),
+    // getOriginalStubFromSpecializedStub(nodeType)
   ].filter(Boolean) as VNodeTypes[]
 
-  if (nodeTypeCandidates.includes(selector)) {
+  // our selector might be a stub itself
+  const target = getOriginalComponentFromStub(selector) ?? selector
+
+  if (nodeTypeCandidates.includes(target)) {
     return true
   }