From 4fe1a95d2953ecf765e27677fa70ebadb176d4c3 Mon Sep 17 00:00:00 2001
From: Evan You <yyx990803@gmail.com>
Date: Fri, 3 Nov 2017 15:40:40 -0400
Subject: [PATCH] fix: properly mark slot rendered flag in production mode

fix #6997
---
 src/core/instance/render-helpers/render-slot.js | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/core/instance/render-helpers/render-slot.js b/src/core/instance/render-helpers/render-slot.js
index 1a194c579e3..a9ef129b729 100644
--- a/src/core/instance/render-helpers/render-slot.js
+++ b/src/core/instance/render-helpers/render-slot.js
@@ -27,12 +27,14 @@ export function renderSlot (
   } else {
     const slotNodes = this.$slots[name]
     // warn duplicate slot usage
-    if (slotNodes && process.env.NODE_ENV !== 'production') {
-      slotNodes._rendered && warn(
-        `Duplicate presence of slot "${name}" found in the same render tree ` +
-        `- this will likely cause render errors.`,
-        this
-      )
+    if (slotNodes) {
+      if (process.env.NODE_ENV !== 'production' && slotNodes._rendered) {
+        warn(
+          `Duplicate presence of slot "${name}" found in the same render tree ` +
+          `- this will likely cause render errors.`,
+          this
+        )
+      }
       slotNodes._rendered = true
     }
     return slotNodes || fallback