fix(runtime-core): enable block tracking when normalizing plain element with slot children (#1987)

fix #1980

packages/runtime-core/src/helpers/renderSlot.ts

@@ -11,6 +11,8 @@ import { PatchFlags, SlotFlags } from '@vue/shared'
 import { warn } from '../warning'
 
 export let isRenderingCompiledSlot = 0
+export const setCompiledSlotRendering = (n: number) =>
+  (isRenderingCompiledSlot += n)
 
 /**
  * Compiler runtime helper for rendering `<slot/>`

packages/runtime-core/src/helpers/withRenderContext.ts

@@ -16,7 +16,7 @@ export function withCtx(
   ctx: ComponentInternalInstance | null = currentRenderingInstance
 ) {
   if (!ctx) return fn
-  return function renderFnWithContext() {
+  const renderFnWithContext = (...args: any[]) => {
     // If a user calls a compiled slot inside a template expression (#1745), it
     // can mess up block tracking, so by default we need to push a null block to
     // avoid that. This isn't necessary if rendering a compiled `<slot>`.
@@ -25,11 +25,13 @@ export function withCtx(
     }
     const owner = currentRenderingInstance
     setCurrentRenderingInstance(ctx)
-    const res = fn.apply(null, arguments as any)
+    const res = fn(...args)
     setCurrentRenderingInstance(owner)
     if (!isRenderingCompiledSlot) {
       closeBlock()
     }
     return res
   }
+  renderFnWithContext._c = true
+  return renderFnWithContext
 }

packages/runtime-core/src/vnode.ts

@@ -36,6 +36,7 @@ import { currentRenderingInstance } from './componentRenderUtils'
 import { RendererNode, RendererElement } from './renderer'
 import { NULL_DYNAMIC_COMPONENT } from './helpers/resolveAssets'
 import { hmrDirtyComponents } from './hmr'
+import { setCompiledSlotRendering } from './helpers/renderSlot'
 
 export const Fragment = (Symbol(__DEV__ ? 'Fragment' : undefined) as any) as {
   __isFragment: true
@@ -539,12 +540,15 @@ export function normalizeChildren(vnode: VNode, children: unknown) {
   } else if (isArray(children)) {
     type = ShapeFlags.ARRAY_CHILDREN
   } else if (typeof children === 'object') {
-    // Normalize slot to plain children
-    if (
-      (shapeFlag & ShapeFlags.ELEMENT || shapeFlag & ShapeFlags.TELEPORT) &&
-      (children as any).default
-    ) {
-      normalizeChildren(vnode, (children as any).default())
+    if (shapeFlag & ShapeFlags.ELEMENT || shapeFlag & ShapeFlags.TELEPORT) {
+      // Normalize slot to plain children for plain element and Teleport
+      const slot = (children as any).default
+      if (slot) {
+        // _c marker is added by withCtx() indicating this is a compiled slot
+        slot._c && setCompiledSlotRendering(1)
+        normalizeChildren(vnode, slot())
+        slot._c && setCompiledSlotRendering(-1)
+      }
       return
     } else {
       type = ShapeFlags.SLOTS_CHILDREN