fix(compiler-dom): comments in the v-if branchs should be ignored when used in Transition (#3622)

fix #3619

packages/compiler-core/src/transforms/vIf.ts

@@ -34,7 +34,7 @@ import {
   OPEN_BLOCK,
   CREATE_VNODE
 } from '../runtimeHelpers'
-import { injectProp, findDir, findProp } from '../utils'
+import { injectProp, findDir, findProp, isBuiltInType } from '../utils'
 import { PatchFlags, PatchFlagNames } from '@vue/shared'
 
 export const transformIf = createStructuralDirectiveTransform(
@@ -146,7 +146,16 @@ export function processIf(
         // move the node to the if node's branches
         context.removeNode()
         const branch = createIfBranch(node, dir)
-        if (__DEV__ && comments.length) {
+        if (
+          __DEV__ &&
+          comments.length &&
+          // #3619 ignore comments if the v-if is direct child of <transition>
+          !(
+            context.parent &&
+            context.parent.type === NodeTypes.ELEMENT &&
+            isBuiltInType(context.parent.tag, 'transition')
+          )
+        ) {
           branch.children = [...comments, ...branch.children]
         }