Fail PUT uploads when the file cannot be closed

main.go

@@ -262,14 +262,20 @@ func handleUpload(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "Failed to create file", http.StatusInternalServerError)
 		return
 	}
-	defer file.Close()
 
 	// MaxBytesReader needs the ResponseWriter the stdlib handed us so it can
 	// mark the connection for close; the logging wrapper would hide it.
 	limitedBody := http.MaxBytesReader(baseWriter(w), r.Body, maxUploadSize)
 	written, err := io.Copy(file, limitedBody)
+	// Closed here rather than in a defer: nothing above returns early, and a
+	// write-back failure only surfacing at close would otherwise arrive after
+	// the 200 and the URL had gone out, leaving the client believing a
+	// truncated file was stored.
+	closeErr := file.Close()
+	if err == nil {
+		err = closeErr
+	}
 	if err != nil {
-		file.Close()
 		os.Remove(targetPath)
 		os.Remove(targetDir)
 		if isMaxBytesError(err) {