refactor(hmr): simplify hmr force update check

packages/runtime-core/src/hmr.ts

@@ -1,5 +1,6 @@
 /* eslint-disable no-restricted-globals */
 import {
+  Component,
   ComponentInternalInstance,
   ComponentOptions,
   InternalRenderFunction
@@ -7,6 +8,10 @@ import {
 import { queueJob, queuePostFlushCb } from './scheduler'
 import { extend } from '@vue/shared'
 
+export let isHmrUpdating = false
+
+export const hmrDirtyComponents = new Set<Component>()
+
 export interface HMRRuntime {
   createRecord: typeof createRecord
   rerender: typeof rerender
@@ -72,9 +77,9 @@ function rerender(id: string, newRender?: Function) {
     }
     instance.renderCache = []
     // this flag forces child components with slot content to update
-    instance.hmrUpdated = true
+    isHmrUpdating = true
     instance.update()
-    instance.hmrUpdated = false
+    isHmrUpdating = false
   })
 }
 
@@ -85,7 +90,7 @@ function reload(id: string, newComp: ComponentOptions) {
   // updates
   Array.from(record).forEach(instance => {
     const comp = instance.type
-    if (!comp.__hmrUpdated) {
+    if (!hmrDirtyComponents.has(comp)) {
       // 1. Update existing comp definition to match new one
       extend(comp, newComp)
       for (const key in comp) {
@@ -95,10 +100,10 @@ function reload(id: string, newComp: ComponentOptions) {
       }
       // 2. Mark component dirty. This forces the renderer to replace the component
       // on patch.
-      comp.__hmrUpdated = true
+      hmrDirtyComponents.add(comp)
       // 3. Make sure to unmark the component after the reload.
       queuePostFlushCb(() => {
-        comp.__hmrUpdated = false
+        hmrDirtyComponents.delete(comp)
       })
     }