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

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'