POC: Plugin interface with wrapper in closure

.gitignore

@@ -1,4 +1,5 @@
+.idea
 node_modules
 yarn-error.log
 dist
-coverage
+coverage

src/config.ts

@@ -0,0 +1,40 @@
+class Pluggable {
+  installedPlugins: any
+  constructor() {
+    this.installedPlugins = []
+  }
+
+  install(handler, options = {}) {
+    if (typeof handler !== 'function') {
+      console.error('plugin.install must receive a function')
+      handler = () => ({})
+    }
+    this.installedPlugins.push({ handler, options })
+  }
+
+  extend(instance) {
+    const invokeSetup = (plugin) => plugin.handler(instance) // invoke the setup method passed to install
+    const bindProperty = ([property, value]: [string, any]) => {
+      instance[property] =
+        typeof value === 'function' ? value.bind(instance) : value
+    }
+    const addAllPropertiesFromSetup = (setupResult) => {
+      setupResult = typeof setupResult === 'object' ? setupResult : {}
+      Object.entries(setupResult).forEach(bindProperty)
+    }
+
+    this.installedPlugins.map(invokeSetup).forEach(addAllPropertiesFromSetup)
+  }
+
+  /** For testing */
+  reset() {
+    this.installedPlugins = []
+  }
+}
+
+export const config = {
+  plugins: {
+    VueWrapper: new Pluggable(),
+    DOMWrapper: new Pluggable()
+  }
+}

src/index.ts

@@ -1,4 +1,7 @@
 import { mount } from './mount'
 import { RouterLinkStub } from './components/RouterLinkStub'
+import { VueWrapper } from './vue-wrapper'
 
-export { mount, RouterLinkStub }
+import { config } from './config'
+
+export { mount, RouterLinkStub, VueWrapper, config }

src/vue-wrapper.ts

@@ -1,5 +1,6 @@
 import { ComponentPublicInstance, nextTick } from 'vue'
 import { ShapeFlags } from '@vue/shared'
+import { config } from './config'
 
 import { DOMWrapper } from './dom-wrapper'
 import { WrapperAPI } from './types'
@@ -21,6 +22,9 @@ export class VueWrapper implements WrapperAPI {
     this.__setProps = setProps
     this.componentVM = this.vm.$refs['VTU_COMPONENT'] as ComponentPublicInstance
     this.__emitted = events
+
+    // plugins hook
+    config.plugins.VueWrapper.extend(this)
   }
 
   private get appRootNode() {
@@ -93,6 +97,15 @@ export class VueWrapper implements WrapperAPI {
     const rootElementWrapper = new DOMWrapper(this.element)
     return rootElementWrapper.trigger(eventString)
   }
+
+  extend() {
+    // plugins hook
+    Object.entries(config.plugins.VueWrapper).forEach(
+      ([name, handler]: [string, () => any]) => {
+        this[name] = handler.bind(this)
+      }
+    )
+  }
 }
 
 export function createWrapper(

tests/features/plugins.spec.ts

@@ -0,0 +1,58 @@
+import { mount, VueWrapper, config } from '../../src'
+
+declare module '../../src/vue-wrapper' {
+  interface VueWrapper {
+    width(): number
+    $el: Element
+  }
+}
+
+const textValue = `I'm the innerHTML`
+const mountComponent = () => mount({ template: `<h1>${textValue}</h1>` })
+
+describe('Plugin', () => {
+  describe('#install method', () => {
+    beforeEach(() => {
+      config.plugins.VueWrapper.reset()
+    })
+
+    it('extends wrappers with the return values from the install function', () => {
+      const width = 230
+      const plugin = () => ({ width })
+      config.plugins.VueWrapper.install(plugin)
+      const wrapper = mountComponent()
+      expect(wrapper).toHaveProperty('width', width)
+    })
+
+    it('receives the wrapper inside the plugin setup', () => {
+      const plugin = (wrapper) => {
+        return {
+          $el: wrapper.element // simple aliases
+        }
+      }
+      config.plugins.VueWrapper.install(plugin)
+      const wrapper = mountComponent()
+      expect(wrapper.$el.innerHTML).toEqual(textValue)
+    })
+
+    describe('error states', () => {
+      const plugins = [
+        () => false,
+        () => true,
+        () => [],
+        true,
+        false,
+        'property',
+        120
+      ]
+
+      it.each(plugins)(
+        'Calling install with %p is handled gracefully',
+        (plugin) => {
+          config.plugins.VueWrapper.install(plugin)
+          expect(() => mountComponent()).not.toThrow()
+        }
+      )
+    })
+  })
+})