From d9bbb6c164a5d8152eca1aeb97ecdb0d4aaad029 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=82=A2=E4=BF=AE=E4=B9=89?= <xingxiuyi@hreeinfo.com>
Date: Wed, 30 Jun 2021 15:05:02 +0800
Subject: [PATCH] fix: Avoid importing in source that __vitePreload has
 declared (close #4016)

---
 packages/vite/src/node/plugins/importAnalysisBuild.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/packages/vite/src/node/plugins/importAnalysisBuild.ts b/packages/vite/src/node/plugins/importAnalysisBuild.ts
index 52faaa095ba120..64dc014c032924 100644
--- a/packages/vite/src/node/plugins/importAnalysisBuild.ts
+++ b/packages/vite/src/node/plugins/importAnalysisBuild.ts
@@ -161,7 +161,11 @@ export function buildImportAnalysisPlugin(config: ResolvedConfig): Plugin {
         }
       }
 
-      if (needPreloadHelper && !ssr) {
+      if (
+        needPreloadHelper &&
+        !ssr &&
+        source.indexOf(`const ${preloadMethod} =`) < 0
+      ) {
         str().prepend(`import { ${preloadMethod} } from "${preloadHelperId}";`)
       }