From 325559e94586bb7b1845308322b877b5138122f0 Mon Sep 17 00:00:00 2001
From: Vladimir <sleuths.slews0s@icloud.com>
Date: Wed, 8 Jul 2026 10:59:59 +0200
Subject: [PATCH] refactor: use a single field for the on-disk transform
 location (#10733)

---
 packages/vitest/src/node/environments/fetchModule.ts | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/packages/vitest/src/node/environments/fetchModule.ts b/packages/vitest/src/node/environments/fetchModule.ts
index cb0975721..ccbce1fb4 100644
--- a/packages/vitest/src/node/environments/fetchModule.ts
+++ b/packages/vitest/src/node/environments/fetchModule.ts
@@ -102,7 +102,7 @@ class ModuleFetcher {
       }
 
       const transformResult = moduleGraphModule.transformResult
-      const tmpPath = transformResult && Reflect.get(transformResult, '_vitest_tmp')
+      const tmpPath = transformResult?.__vitestTmp
       if (typeof tmpPath === 'string') {
         return getCachedResult(result, tmpPath)
       }
@@ -118,7 +118,7 @@ class ModuleFetcher {
       const tmpFile = join(tmpDir, hash('sha1', result.id, 'hex'))
       return this.cacheResult(result, tmpFile).then((result) => {
         if (transformResult) {
-          Reflect.set(transformResult, '_vitest_tmp', tmpFile)
+          transformResult.__vitestTmp = tmpFile
         }
         return result
       })
@@ -569,6 +569,8 @@ export function handleRollupError(e: unknown): never {
 
 declare module 'vite' {
   export interface TransformResult {
+    // on-disk location of the transformed code, written by either the
+    // `experimental.fsModuleCache` store or the forks pool's tmp copies
     __vitestTmp?: string
     __vitestModuleType?: ModuleType
   }
-- 
2.51.2