From 602b58ebd1923dd48669755d5f5b67c5478cc625 Mon Sep 17 00:00:00 2001
From: HcySunYang <HcySunYang@outlook.com>
Date: Tue, 23 Mar 2021 04:34:46 +0800
Subject: [PATCH] fix(compiler-core): fix the detection of forwarded slots with
 v-if or v-for (#3353)

fix #3347
---
 .../__tests__/transforms/vSlot.spec.ts        | 21 ++++++++++++---
 .../compiler-core/src/transforms/vSlot.ts     | 27 +++++++++++++------
 2 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/packages/compiler-core/__tests__/transforms/vSlot.spec.ts b/packages/compiler-core/__tests__/transforms/vSlot.spec.ts
index a14198c8adc..99fc009b504 100644
--- a/packages/compiler-core/__tests__/transforms/vSlot.spec.ts
+++ b/packages/compiler-core/__tests__/transforms/vSlot.spec.ts
@@ -15,6 +15,7 @@ import { transformElement } from '../../src/transforms/transformElement'
 import { transformOn } from '../../src/transforms/vOn'
 import { transformBind } from '../../src/transforms/vBind'
 import { transformExpression } from '../../src/transforms/transformExpression'
+import { transformSlotOutlet } from '../../src/transforms/transformSlotOutlet'
 import {
   trackSlotScopes,
   trackVForSlotScopes
@@ -34,6 +35,7 @@ function parseWithSlots(template: string, options: CompilerOptions = {}) {
       ...(options.prefixIdentifiers
         ? [trackVForSlotScopes, transformExpression]
         : []),
+      transformSlotOutlet,
       transformElement,
       trackSlotScopes
     ],
@@ -737,9 +739,8 @@ describe('compiler: transform component slots', () => {
     expect(generate(root, { prefixIdentifiers: true }).code).toMatchSnapshot()
   })
 
-  test('generate flag on forwarded slots', () => {
-    const { slots } = parseWithSlots(`<Comp><slot/></Comp>`)
-    expect(slots).toMatchObject({
+  describe('forwarded slots', () => {
+    const toMatch = {
       type: NodeTypes.JS_OBJECT_EXPRESSION,
       properties: [
         {
@@ -751,6 +752,20 @@ describe('compiler: transform component slots', () => {
           value: { content: `3 /* FORWARDED */` }
         }
       ]
+    }
+    test('<slot> tag only', () => {
+      const { slots } = parseWithSlots(`<Comp><slot/></Comp>`)
+      expect(slots).toMatchObject(toMatch)
+    })
+
+    test('<slot> tag w/ v-if', () => {
+      const { slots } = parseWithSlots(`<Comp><slot v-if="ok"/></Comp>`)
+      expect(slots).toMatchObject(toMatch)
+    })
+
+    test('<slot> tag w/ v-for', () => {
+      const { slots } = parseWithSlots(`<Comp><slot v-for="a in b"/></Comp>`)
+      expect(slots).toMatchObject(toMatch)
     })
   })
 
diff --git a/packages/compiler-core/src/transforms/vSlot.ts b/packages/compiler-core/src/transforms/vSlot.ts
index 8e1596a2e9a..e6387be6c33 100644
--- a/packages/compiler-core/src/transforms/vSlot.ts
+++ b/packages/compiler-core/src/transforms/vSlot.ts
@@ -368,14 +368,25 @@ function buildDynamicSlot(
 function hasForwardedSlots(children: TemplateChildNode[]): boolean {
   for (let i = 0; i < children.length; i++) {
     const child = children[i]
-    if (child.type === NodeTypes.ELEMENT) {
-      if (
-        child.tagType === ElementTypes.SLOT ||
-        (child.tagType === ElementTypes.ELEMENT &&
-          hasForwardedSlots(child.children))
-      ) {
-        return true
-      }
+    switch (child.type) {
+      case NodeTypes.ELEMENT:
+        if (
+          child.tagType === ElementTypes.SLOT ||
+          (child.tagType === ElementTypes.ELEMENT &&
+            hasForwardedSlots(child.children))
+        ) {
+          return true
+        }
+        break
+      case NodeTypes.IF:
+        if (hasForwardedSlots(child.branches)) return true
+        break
+      case NodeTypes.IF_BRANCH:
+      case NodeTypes.FOR:
+        if (hasForwardedSlots(child.children)) return true
+        break
+      default:
+        break
     }
   }
   return false