From ef50c333ce0d6b48dfc9e1f1219f26d6f2406e76 Mon Sep 17 00:00:00 2001
From: Evan You <yyx990803@gmail.com>
Date: Thu, 12 Dec 2019 17:58:32 -0500
Subject: [PATCH] fix(core): generate fragment root with patchFlag + optimize
 fragment w/ patchFlag

---
 packages/compiler-core/src/transform.ts       | 13 +++++++++++--
 packages/compiler-core/src/transforms/vFor.ts |  2 +-
 packages/runtime-core/src/renderer.ts         |  1 +
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/packages/compiler-core/src/transform.ts b/packages/compiler-core/src/transform.ts
index 0c01cd84..dfa73edc 100644
--- a/packages/compiler-core/src/transform.ts
+++ b/packages/compiler-core/src/transform.ts
@@ -18,7 +18,13 @@ import {
   CacheExpression,
   createCacheExpression
 } from './ast'
-import { isString, isArray, NOOP } from '@vue/shared'
+import {
+  isString,
+  isArray,
+  NOOP,
+  PatchFlags,
+  PatchFlagNames
+} from '@vue/shared'
 import { defaultOnError } from './errors'
 import {
   TO_STRING,
@@ -283,7 +289,10 @@ function finalizeRoot(root: RootNode, context: TransformContext) {
       createCallExpression(helper(CREATE_BLOCK), [
         helper(FRAGMENT),
         `null`,
-        root.children
+        root.children,
+        `${PatchFlags.UNKEYED_FRAGMENT} /* ${
+          PatchFlagNames[PatchFlags.UNKEYED_FRAGMENT]
+        } */`
       ]),
       context
     )
diff --git a/packages/compiler-core/src/transforms/vFor.ts b/packages/compiler-core/src/transforms/vFor.ts
index c09a19f1..418999cb 100644
--- a/packages/compiler-core/src/transforms/vFor.ts
+++ b/packages/compiler-core/src/transforms/vFor.ts
@@ -79,7 +79,7 @@ export const transformFor = createStructuralDirectiveTransform(
         helper(FRAGMENT),
         `null`,
         renderExp,
-        fragmentFlag + (__DEV__ ? ` /* ${PatchFlagNames[fragmentFlag]} */` : ``)
+        `${fragmentFlag} /* ${PatchFlagNames[fragmentFlag]} */`
       ])
     ]) as ForCodegenNode
 
diff --git a/packages/runtime-core/src/renderer.ts b/packages/runtime-core/src/renderer.ts
index b688525d..d3c38c3d 100644
--- a/packages/runtime-core/src/renderer.ts
+++ b/packages/runtime-core/src/renderer.ts
@@ -1033,6 +1033,7 @@ export function createRenderer<
     }
     // fast path
     if (patchFlag > 0) {
+      optimized = true
       if (patchFlag & PatchFlags.KEYED_FRAGMENT) {
         // this could be either fully-keyed or mixed (some keyed some not)
         // presence of patchFlag means children are guaranteed to be arrays