From 9c3d4a6e2c944eefe497fda1a64bbd05dfc5b879 Mon Sep 17 00:00:00 2001
From: fxy060608 <fxy060608@gmail.com>
Date: Sun, 26 Jun 2022 01:58:50 +0800
Subject: [PATCH] fix(mp): pre watchers triggered synchronously (#3648)

---
 packages/uni-mp-vue/lib/vue.runtime.esm.js | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/packages/uni-mp-vue/lib/vue.runtime.esm.js b/packages/uni-mp-vue/lib/vue.runtime.esm.js
index db12bdfe1..0c20bc171 100644
--- a/packages/uni-mp-vue/lib/vue.runtime.esm.js
+++ b/packages/uni-mp-vue/lib/vue.runtime.esm.js
@@ -2022,7 +2022,17 @@ function doWatch(source, cb, { immediate, deep, flush, onTrack, onTrigger } = EM
     }
     else {
         // default: 'pre'
-        scheduler = () => queuePreFlushCb(job);
+        scheduler = () => {
+            if (!instance || instance.isMounted) {
+                queuePreFlushCb(job);
+            }
+            else {
+                // with 'pre' option, the first call must happen before
+                // the component is mounted so it is called synchronously.
+                // fixed by xxxxxx https://github.com/dcloudio/uni-app/issues/3648
+                job();
+            }
+        };
     }
     const effect = new ReactiveEffect(getter, scheduler);
     if ((process.env.NODE_ENV !== 'production')) {
-- 
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