feat(core): support v-show directive (#310)

packages/runtime-dom/__tests__/directives/vShow.spec.ts

@@ -0,0 +1,128 @@
+import {
+  withDirectives,
+  createComponent,
+  h,
+  nextTick,
+  VNode
+} from '@vue/runtime-core'
+import { createApp, vShow } from '@vue/runtime-dom'
+
+const withVShow = (node: VNode, exp: any) =>
+  withDirectives(node, [[vShow, exp]])
+
+let app: any, root: any
+
+beforeEach(() => {
+  app = createApp()
+  root = document.createElement('div') as any
+})
+
+describe('runtime-dom: v-show directive', () => {
+  test('should check show value is truthy', async () => {
+    const component = createComponent({
+      data() {
+        return { value: true }
+      },
+      render() {
+        return [withVShow(h('div'), this.value)]
+      }
+    })
+    app.mount(component, root)
+
+    const $div = root.querySelector('div')
+
+    expect($div.style.display).toEqual('')
+  })
+
+  test('should check show value is falsy', async () => {
+    const component = createComponent({
+      data() {
+        return { value: false }
+      },
+      render() {
+        return [withVShow(h('div'), this.value)]
+      }
+    })
+    app.mount(component, root)
+
+    const $div = root.querySelector('div')
+
+    expect($div.style.display).toEqual('none')
+  })
+
+  it('should update show value changed', async () => {
+    const component = createComponent({
+      data() {
+        return { value: true }
+      },
+      render() {
+        return [withVShow(h('div'), this.value)]
+      }
+    })
+    app.mount(component, root)
+
+    const $div = root.querySelector('div')
+    const data = root._vnode.component.data
+
+    expect($div.style.display).toEqual('')
+
+    data.value = false
+    await nextTick()
+    expect($div.style.display).toEqual('none')
+
+    data.value = {}
+    await nextTick()
+    expect($div.style.display).toEqual('')
+
+    data.value = 0
+    await nextTick()
+    expect($div.style.display).toEqual('none')
+
+    data.value = []
+    await nextTick()
+    expect($div.style.display).toEqual('')
+
+    data.value = null
+    await nextTick()
+    expect($div.style.display).toEqual('none')
+
+    data.value = '0'
+    await nextTick()
+    expect($div.style.display).toEqual('')
+
+    data.value = undefined
+    await nextTick()
+    expect($div.style.display).toEqual('none')
+
+    data.value = 1
+    await nextTick()
+    expect($div.style.display).toEqual('')
+  })
+
+  test('should respect display value in style attribute', async () => {
+    const component = createComponent({
+      data() {
+        return { value: true }
+      },
+      render() {
+        return [
+          withVShow(h('div', { style: { display: 'block' } }), this.value)
+        ]
+      }
+    })
+    app.mount(component, root)
+
+    const $div = root.querySelector('div')
+    const data = root._vnode.component.data
+
+    expect($div.style.display).toEqual('block')
+
+    data.value = false
+    await nextTick()
+    expect($div.style.display).toEqual('none')
+
+    data.value = true
+    await nextTick()
+    expect($div.style.display).toEqual('block')
+  })
+})

packages/runtime-dom/src/directives/vShow.ts

@@ -0,0 +1,45 @@
+import { ObjectDirective } from '@vue/runtime-core'
+
+interface VShowElement extends HTMLElement {
+  // _vod = vue original display
+  _vod: string
+}
+
+export const vShow: ObjectDirective<VShowElement> = {
+  beforeMount(el, { value }, { transition }) {
+    el._vod = el.style.display === 'none' ? '' : el.style.display
+    if (transition && value) {
+      transition.beforeEnter(el)
+    } else {
+      setDisplay(el, value)
+    }
+  },
+  mounted(el, { value }, { transition }) {
+    if (transition && value) {
+      transition.enter(el)
+    }
+  },
+  updated(el, { value, oldValue }, { transition }) {
+    if (!value === !oldValue) return
+    if (transition) {
+      if (value) {
+        transition.beforeEnter(el)
+        setDisplay(el, true)
+        transition.enter(el)
+      } else {
+        transition.leave(el, () => {
+          setDisplay(el, false)
+        })
+      }
+    } else {
+      setDisplay(el, value)
+    }
+  },
+  beforeUnmount(el) {
+    setDisplay(el, true)
+  }
+}
+
+function setDisplay(el: VShowElement, value: unknown): void {
+  el.style.display = value ? el._vod : 'none'
+}

packages/runtime-dom/src/index.ts

@@ -68,6 +68,8 @@ export { withModifiers, withKeys } from './directives/vOn'
 // DOM-only components
 export { Transition, TransitionProps } from './components/Transition'
 
+export { vShow } from './directives/vShow'
+
 // re-export everything from core
 // h, Component, reactivity API, nextTick, flags & types
 export * from '@vue/runtime-core'