From cc9c2da7b816a41987000dd662f04dbc2033a600 Mon Sep 17 00:00:00 2001
From: Artur <artur@vaadin.com>
Date: Thu, 28 Oct 2021 11:00:52 +0300
Subject: [PATCH] fix: do not overwrite pendingReload promise (fix #5448)
 (#5452)

---
 .../src/node/optimizer/registerMissing.ts     | 22 +++++++++++++------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/packages/vite/src/node/optimizer/registerMissing.ts b/packages/vite/src/node/optimizer/registerMissing.ts
index 6883fc9f262a81..6071228b566f30 100644
--- a/packages/vite/src/node/optimizer/registerMissing.ts
+++ b/packages/vite/src/node/optimizer/registerMissing.ts
@@ -15,7 +15,7 @@ export function createMissingImporterRegisterFn(
   const { logger } = server.config
   let knownOptimized = server._optimizeDepsMetadata!.optimized
   let currentMissing: Record<string, string> = {}
-  let handle: NodeJS.Timeout
+  let handle: NodeJS.Timeout | undefined
 
   let pendingResolve: (() => void) | null = null
 
@@ -70,8 +70,11 @@ export function createMissingImporterRegisterFn(
       )
     } finally {
       server._isRunningOptimizer = false
-      pendingResolve && pendingResolve()
-      server._pendingReload = pendingResolve = null
+      if (!handle) {
+        // No other rerun() pending so resolve and let pending requests proceed
+        pendingResolve && pendingResolve()
+        server._pendingReload = pendingResolve = null
+      }
     }
 
     // Cached transform results have stale imports (resolved to
@@ -93,10 +96,15 @@ export function createMissingImporterRegisterFn(
     if (!knownOptimized[id]) {
       currentMissing[id] = resolved
       if (handle) clearTimeout(handle)
-      handle = setTimeout(() => rerun(ssr), debounceMs)
-      server._pendingReload = new Promise((r) => {
-        pendingResolve = r
-      })
+      handle = setTimeout(() => {
+        handle = undefined
+        rerun(ssr)
+      }, debounceMs)
+      if (!server._pendingReload) {
+        server._pendingReload = new Promise((r) => {
+          pendingResolve = r
+        })
+      }
     }
   }
 }