fix(runtime-core): should not track dynamic children when the user calls a compiled slot inside template expression (#3554)

fix #3548, partial fix for #3569

packages/runtime-core/src/componentRenderContext.ts

@@ -1,7 +1,6 @@
 import { ComponentInternalInstance } from './component'
 import { devtoolsComponentUpdated } from './devtools'
-import { isRenderingCompiledSlot } from './helpers/renderSlot'
-import { closeBlock, openBlock } from './vnode'
+import { setBlockTracking } from './vnode'
 
 /**
  * mark the current rendering instance for asset resolution (e.g.
@@ -56,6 +55,14 @@ export function popScopeId() {
  */
 export const withScopeId = (_id: string) => withCtx
 
+export type ContextualRenderFn = {
+  (...args: any[]): any
+  _n: boolean /* already normalized */
+  _c: boolean /* compiled */
+  _d: boolean /* disableTracking */
+  _ns: boolean /* nonScoped */
+}
+
 /**
  * Wrap a slot function to memoize current rendering instance
  * @private compiler helper
@@ -66,18 +73,26 @@ export function withCtx(
   isNonScopedSlot?: boolean // __COMPAT__ only
 ) {
   if (!ctx) return fn
-  const renderFnWithContext = (...args: any[]) => {
+
+  // already normalized
+  if ((fn as ContextualRenderFn)._n) {
+    return fn
+  }
+
+  const renderFnWithContext: ContextualRenderFn = (...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>`.
-    if (!isRenderingCompiledSlot) {
-      openBlock(true /* null block that disables tracking */)
+    // can mess up block tracking, so by default we disable block tracking and
+    // force bail out when invoking a compiled slot (indicated by the ._d flag).
+    // This isn't necessary if rendering a compiled `<slot>`, so we flip the
+    // ._d flag off when invoking the wrapped fn inside `renderSlot`.
+    if (renderFnWithContext._d) {
+      setBlockTracking(-1)
     }
     const prevInstance = setCurrentRenderingInstance(ctx)
     const res = fn(...args)
     setCurrentRenderingInstance(prevInstance)
-    if (!isRenderingCompiledSlot) {
-      closeBlock()
+    if (renderFnWithContext._d) {
+      setBlockTracking(1)
     }
 
     if (__DEV__ || __FEATURE_PROD_DEVTOOLS__) {
@@ -86,13 +101,18 @@ export function withCtx(
 
     return res
   }
-  // mark this as a compiled slot function.
+
+  // mark normalized to avoid duplicated wrapping
+  renderFnWithContext._n = true
+  // mark this as compiled by default
   // this is used in vnode.ts -> normalizeChildren() to set the slot
   // rendering flag.
-  // also used to cache the normalized results to avoid repeated normalization
-  renderFnWithContext._c = renderFnWithContext
+  renderFnWithContext._c = true
+  // disable block tracking by default
+  renderFnWithContext._d = true
+  // compat build only flag to distinguish scoped slots from non-scoped ones
   if (__COMPAT__ && isNonScopedSlot) {
-    renderFnWithContext._nonScoped = true
+    renderFnWithContext._ns = true
   }
   return renderFnWithContext
 }