fix: handle EPERM on chmod during atomic writes for Windows/Docker #53947

Justin Skywork · Justin Skywork · commit bc3f5681f792 · 2026-03-24T17:20:31.000-04:00
diff --git a/src/shared/fs-atomic-fix.ts b/src/shared/fs-atomic-fix.ts
@@ -0,0 +1,19 @@
+import fs from "fs";
+
+/**
+ * Handles EPERM issues during chmod on Windows-mounted Docker volumes.
+ * Addresses #53947.
+ */
+export function writeTextFileAtomicSync(pathname: string, value: string, mode: number = 0o600) {
+    const tempPath = `${pathname}.tmp-${process.pid}-${Date.now()}`;
+    fs.writeFileSync(tempPath, value, "utf8");
+    
+    try {
+        // This fails on Windows-mounted volumes in Docker
+        fs.chmodSync(tempPath, mode);
+    } catch (e) {
+        // Silently continue if chmod fails (EPERM expected on NTFS/CIFS mounts)
+    }
+    
+    fs.renameSync(tempPath, pathname);
+}
