fix(build): improve built-in components treeshakability

packages/runtime-core/src/components/KeepAlive.ts

@@ -362,13 +362,16 @@ const KeepAliveImpl: ComponentOptions = {
   },
 }
 
-if (__COMPAT__) {
-  KeepAliveImpl.__isBuildIn = true
+const decorate = (t: typeof KeepAliveImpl) => {
+  t.__isBuiltIn = true
+  return t
 }
 
 // export the public type for h/tsx inference
 // also to avoid inline import() in generated d.ts files
-export const KeepAlive = KeepAliveImpl as any as {
+export const KeepAlive = (__COMPAT__
+  ? /*#__PURE__*/ decorate(KeepAliveImpl)
+  : KeepAliveImpl) as any as {
   __isKeepAlive: true
   new (): {
     $props: VNodeProps & KeepAliveProps

packages/runtime-dom/src/components/Transition.ts

@@ -42,19 +42,6 @@ export interface ElementWithTransition extends HTMLElement {
   [vtcKey]?: Set<string>
 }
 
-// DOM Transition is a higher-order-component based on the platform-agnostic
-// base Transition component, with DOM-specific logic.
-export const Transition: FunctionalComponent<TransitionProps> = (
-  props,
-  { slots },
-) => h(BaseTransition, resolveTransitionProps(props), slots)
-
-Transition.displayName = 'Transition'
-
-if (__COMPAT__) {
-  Transition.__isBuiltIn = true
-}
-
 const DOMTransitionPropsValidators = {
   name: String,
   type: String,
@@ -74,12 +61,33 @@ const DOMTransitionPropsValidators = {
   leaveToClass: String,
 }
 
-export const TransitionPropsValidators: any = (Transition.props =
-  /*#__PURE__*/ extend(
-    {},
-    BaseTransitionPropsValidators as any,
-    DOMTransitionPropsValidators,
-  ))
+export const TransitionPropsValidators: any = /*#__PURE__*/ extend(
+  {},
+  BaseTransitionPropsValidators as any,
+  DOMTransitionPropsValidators,
+)
+
+/**
+ * Wrap logic that attaches extra properties to Transition in a function
+ * so that it can be annotated as pure
+ */
+const decorate = (t: typeof Transition) => {
+  t.displayName = 'Transition'
+  t.props = TransitionPropsValidators
+  if (__COMPAT__) {
+    t.__isBuiltIn = true
+  }
+  return t
+}
+
+/**
+ * DOM Transition is a higher-order-component based on the platform-agnostic
+ * base Transition component, with DOM-specific logic.
+ */
+export const Transition: FunctionalComponent<TransitionProps> =
+  /*#__PURE__*/ decorate((props, { slots }) =>
+    h(BaseTransition, resolveTransitionProps(props), slots),
+  )
 
 /**
  * #3227 Incoming hooks may be merged into arrays when wrapping Transition

packages/runtime-dom/src/components/TransitionGroup.ts

@@ -32,12 +32,27 @@ const positionMap = new WeakMap<VNode, DOMRect>()
 const newPositionMap = new WeakMap<VNode, DOMRect>()
 const moveCbKey = Symbol('_moveCb')
 const enterCbKey = Symbol('_enterCb')
+
 export type TransitionGroupProps = Omit<TransitionProps, 'mode'> & {
   tag?: string
   moveClass?: string
 }
 
-const TransitionGroupImpl: ComponentOptions = {
+/**
+ * Wrap logic that modifies TransitionGroup properties in a function
+ * so that it can be annotated as pure
+ */
+const decorate = (t: typeof TransitionGroupImpl) => {
+  // TransitionGroup does not support "mode" so we need to remove it from the
+  // props declarations, but direct delete operation is considered a side effect
+  delete t.props.mode
+  if (__COMPAT__) {
+    t.__isBuiltIn = true
+  }
+  return t
+}
+
+const TransitionGroupImpl: ComponentOptions = /*#__PURE__*/ decorate({
   name: 'TransitionGroup',
 
   props: /*#__PURE__*/ extend({}, TransitionPropsValidators, {
@@ -152,20 +167,7 @@ const TransitionGroupImpl: ComponentOptions = {
       return createVNode(tag, null, children)
     }
   },
-}
-
-if (__COMPAT__) {
-  TransitionGroupImpl.__isBuiltIn = true
-}
-
-/**
- * TransitionGroup does not support "mode" so we need to remove it from the
- * props declarations, but direct delete operation is considered a side effect
- * and will make the entire transition feature non-tree-shakeable, so we do it
- * in a function and mark the function's invocation as pure.
- */
-const removeMode = (props: any) => delete props.mode
-/*#__PURE__*/ removeMode(TransitionGroupImpl.props)
+})
 
 export const TransitionGroup = TransitionGroupImpl as unknown as {
   new (): {