fix(compiler): generate correct fragment children when it contains single text node or slot outlet

packages/compiler-core/__tests__/__snapshots__/compile.spec.ts.snap

@@ -14,7 +14,9 @@ return function render() {
       _toString(world.burn()),
       (_openBlock(), ok
         ? _createBlock(\\"div\\", { key: 0 }, \\"yes\\")
-        : _createBlock(_Fragment, { key: 1 }, \\"no\\")),
+        : _createBlock(_Fragment, { key: 1 }, [
+            \\"no\\"
+          ])),
       _createVNode(_Fragment, null, _renderList(list, (value, index) => {
         return (_openBlock(), _createBlock(\\"div\\", null, [
           _createVNode(\\"span\\", null, _toString(value + index))
@@ -37,7 +39,9 @@ return function render() {
     toString(_ctx.world.burn()),
     (openBlock(), (_ctx.ok)
       ? createBlock(\\"div\\", { key: 0 }, \\"yes\\")
-      : createBlock(Fragment, { key: 1 }, \\"no\\")),
+      : createBlock(Fragment, { key: 1 }, [
+          \\"no\\"
+        ])),
     createVNode(Fragment, null, renderList(_ctx.list, (value, index) => {
       return (openBlock(), createBlock(\\"div\\", null, [
         createVNode(\\"span\\", null, toString(value + index))
@@ -59,7 +63,9 @@ export default function render() {
     _toString(_ctx.world.burn()),
     (openBlock(), (_ctx.ok)
       ? createBlock(\\"div\\", { key: 0 }, \\"yes\\")
-      : createBlock(Fragment, { key: 1 }, \\"no\\")),
+      : createBlock(Fragment, { key: 1 }, [
+          \\"no\\"
+        ])),
     createVNode(Fragment, null, renderList(_ctx.list, (value, index) => {
       return (openBlock(), createBlock(\\"div\\", null, [
         createVNode(\\"span\\", null, _toString(value + index))

packages/compiler-core/__tests__/transforms/__snapshots__/vFor.spec.ts.snap

@@ -104,6 +104,20 @@ return function render() {
 }"
 `;
 
+exports[`compiler: v-for codegen template v-for w/ <slot/> 1`] = `
+"const _Vue = Vue
+
+return function render() {
+  with (this) {
+    const { renderList: _renderList, createVNode: _createVNode, Fragment: _Fragment, renderSlot: _renderSlot, openBlock: _openBlock, createBlock: _createBlock } = _Vue
+    
+    return _createVNode(_Fragment, null, _renderList(items, (item) => {
+      return (_openBlock(), _createBlock(_Fragment, null, _renderSlot($slots.default)))
+    }), 128 /* UNKEYED_FRAGMENT */)
+  }
+}"
+`;
+
 exports[`compiler: v-for codegen v-if + v-for 1`] = `
 "const _Vue = Vue
 

packages/compiler-core/__tests__/transforms/__snapshots__/vIf.spec.ts.snap

@@ -32,6 +32,20 @@ return function render() {
 }"
 `;
 
+exports[`compiler: v-if codegen template v-if w/ single <slot/> child 1`] = `
+"const _Vue = Vue
+
+return function render() {
+  with (this) {
+    const { openBlock: _openBlock, renderSlot: _renderSlot, Fragment: _Fragment, createBlock: _createBlock, Empty: _Empty } = _Vue
+    
+    return (_openBlock(), ok
+      ? _createBlock(_Fragment, { key: 0 }, _renderSlot($slots.default))
+      : _createBlock(_Empty))
+  }
+}"
+`;
+
 exports[`compiler: v-if codegen v-if + v-else 1`] = `
 "const _Vue = Vue
 
@@ -57,7 +71,9 @@ return function render() {
       ? _createBlock(\\"div\\", { key: 0 })
       : orNot
         ? _createBlock(\\"p\\", { key: 1 })
-        : _createBlock(_Fragment, { key: 2 }, \\"fine\\"))
+        : _createBlock(_Fragment, { key: 2 }, [
+            \\"fine\\"
+          ]))
   }
 }"
 `;

packages/compiler-core/__tests__/transforms/vFor.spec.ts

@@ -4,6 +4,7 @@ import { transformIf } from '../../src/transforms/vIf'
 import { transformFor } from '../../src/transforms/vFor'
 import { transformBind } from '../../src/transforms/vBind'
 import { transformElement } from '../../src/transforms/transformElement'
+import { transformSlotOutlet } from '../../src/transforms/transfromSlotOutlet'
 import { transformExpression } from '../../src/transforms/transformExpression'
 import {
   ForNode,
@@ -20,7 +21,8 @@ import {
   CREATE_BLOCK,
   FRAGMENT,
   RENDER_LIST,
-  CREATE_VNODE
+  CREATE_VNODE,
+  RENDER_SLOT
 } from '../../src/runtimeConstants'
 import { PatchFlags } from '@vue/runtime-dom'
 import { PatchFlagNames } from '@vue/shared'
@@ -36,6 +38,7 @@ function parseWithForTransform(
       transformIf,
       transformFor,
       ...(options.prefixIdentifiers ? [transformExpression] : []),
+      transformSlotOutlet,
       transformElement
     ],
     directiveTransforms: {
@@ -692,6 +695,28 @@ describe('compiler: v-for', () => {
       expect(generate(root).code).toMatchSnapshot()
     })
 
+    test('template v-for w/ <slot/>', () => {
+      const {
+        root,
+        node: { codegenNode }
+      } = parseWithForTransform(
+        '<template v-for="item in items"><slot/></template>'
+      )
+      expect(assertSharedCodegen(codegenNode)).toMatchObject({
+        source: { content: `items` },
+        params: [{ content: `item` }],
+        blockArgs: [
+          `_${FRAGMENT}`,
+          `null`,
+          {
+            type: NodeTypes.JS_CALL_EXPRESSION,
+            callee: `_${RENDER_SLOT}`
+          }
+        ]
+      })
+      expect(generate(root).code).toMatchSnapshot()
+    })
+
     test('keyed v-for', () => {
       const {
         root,

packages/compiler-core/__tests__/transforms/vIf.spec.ts

@@ -2,6 +2,7 @@ import { parse } from '../../src/parse'
 import { transform } from '../../src/transform'
 import { transformIf } from '../../src/transforms/vIf'
 import { transformElement } from '../../src/transforms/transformElement'
+import { transformSlotOutlet } from '../../src/transforms/transfromSlotOutlet'
 import {
   IfNode,
   NodeTypes,
@@ -21,7 +22,8 @@ import {
   EMPTY,
   FRAGMENT,
   MERGE_PROPS,
-  APPLY_DIRECTIVES
+  APPLY_DIRECTIVES,
+  RENDER_SLOT
 } from '../../src/runtimeConstants'
 import { createObjectMatcher } from '../testUtils'
 
@@ -32,7 +34,7 @@ function parseWithIfTransform(
 ) {
   const ast = parse(template, options)
   transform(ast, {
-    nodeTransforms: [transformIf, transformElement],
+    nodeTransforms: [transformIf, transformSlotOutlet, transformElement],
     ...options
   })
   if (!options.onError) {
@@ -344,6 +346,25 @@ describe('compiler: v-if', () => {
       expect(generate(root).code).toMatchSnapshot()
     })
 
+    test('template v-if w/ single <slot/> child', () => {
+      const {
+        root,
+        node: { codegenNode }
+      } = parseWithIfTransform(`<template v-if="ok"><slot/></template>`)
+      assertSharedCodegen(codegenNode)
+      const branch1 = (codegenNode.expressions[1] as ConditionalExpression)
+        .consequent as CallExpression
+      expect(branch1.arguments).toMatchObject([
+        `_${FRAGMENT}`,
+        `{ key: 0 }`,
+        {
+          type: NodeTypes.JS_CALL_EXPRESSION,
+          callee: `_${RENDER_SLOT}`
+        }
+      ])
+      expect(generate(root).code).toMatchSnapshot()
+    })
+
     test('v-if + v-else', () => {
       const {
         root,