test: add test case

Author: edison1105

packages/runtime-core/__tests__/rendererOptimizedMode.spec.ts

@@ -23,7 +23,9 @@ import {
   createApp,
   FunctionalComponent,
   renderList,
-  onUnmounted
+  onUnmounted,
+  createElementBlock,
+  createElementVNode
 } from '@vue/runtime-test'
 import { PatchFlags, SlotFlags } from '@vue/shared'
 import { SuspenseImpl } from '../src/components/Suspense'
@@ -697,6 +699,83 @@ describe('renderer: optimized mode', () => {
     )
   })
 
+  test('should not track dynamic children for slot fallback nodes', async () => {
+    const Comp = {
+      props: ['show'],
+      setup(props: any, { slots }: SetupContext) {
+        return () => {
+          return (
+            openBlock(),
+            createElementBlock('div', null, [
+              renderSlot(slots, 'default', { hide: !props.show }, () => [
+                true
+                  ? (openBlock(),
+                    (block = createElementBlock(
+                      Fragment,
+                      { key: 0 },
+                      [createTextVNode('foo')],
+                      PatchFlags.STABLE_FRAGMENT
+                    )))
+                  : createCommentVNode('v-if', true)
+              ])
+            ])
+          )
+        }
+      }
+    }
+
+    const show = ref(true)
+    const app = createApp({
+      render() {
+        return (
+          openBlock(),
+          createBlock(
+            Comp,
+            { show: show.value },
+            {
+              default: withCtx(({ hide }: { hide: boolean }) => [
+                !hide
+                  ? (openBlock(),
+                    createElementBlock(
+                      Fragment,
+                      { key: 0 },
+                      [
+                        createCommentVNode('comment'),
+                        createElementVNode(
+                          'div',
+                          null,
+                          'bar',
+                          PatchFlags.HOISTED
+                        )
+                      ],
+                      PatchFlags.STABLE_FRAGMENT
+                    ))
+                  : createCommentVNode('v-if', true)
+              ]),
+              _: SlotFlags.STABLE
+            },
+            PatchFlags.PROPS,
+            ['show']
+          )
+        )
+      }
+    })
+
+    app.mount(root)
+    expect(inner(root)).toBe('<div><!--comment--><div>bar</div></div>')
+    expect(block).toBe(null)
+
+    show.value = false
+    await nextTick()
+    expect(block!.dynamicChildren).toBe(null)
+    expect(inner(root)).toBe('<div>foo</div>')
+
+    show.value = true
+    await nextTick()
+    expect(block!.dynamicChildren).toBe(null)
+    expect(inner(root)).toBe('<div><!--comment--><div>bar</div></div>')
+  })
+
   // 3569
   test('should force bailout when the user manually calls the slot function', async () => {
     const index = ref(0)