我改写了下，为了能用 / 区分文件和文件夹：
(defun simple-http-server (root-dir)
"简单的文件 HTTP 服务器，效果类似于 python -m http.server 8888."
(interactive (list (expand-file-name default-directory)))
(ws-start
`(lambda (request)
(with-slots ((proc process) headers) request
(let* ((path (alist-get :GET headers))
(path (concat ,root-dir path)))
(cond ((file-directory-p path)
(ws-response-header proc 200 (cons "Content-type" "text/html"))
(process-send-string
proc
(mapconcat
(lambda (f)
(when (file-directory-p f)
(setq f (concat f "/")))
(format "<li><a href=%s>%s</li>"
(url-encode-url f) (url-encode-url f)))
(directory-files path)
"\n")))
((file-regular-p path)
(ws-send-file proc path))
(t
(ws-send-404 proc)))
)))
8888)
(browse-url "http://localhost:8888/"))
