Emacs25.1之后UrlHttpError

Posted 2020-08-27 西西弗斯的痛苦与无聊

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1. 引言
2. 正文
3. 参考资源

1 引言

当我们更新到Emacs25.1或者之后的版本后，原来可以使用的org2blog，或者其他类似使用metaweblog包的功能都无法使用了，会报一个"error: url-http-create-request: Multibyte text in HTTP request" 的错误信息。

这个问题出现之后，由于我用的是cnblogs插件，这个插件作者很久没有更新了，我首先想到的是这个插件是不是出问题了。然后，我把这个插件查找了，发现不是这个里面的问题。于是在google上搜索了一下，发现其他有好多人也在问这个问题（主要是日本的，说明emacs在日本使用普及度应该比中国要高很多）。

2 正文

在网上并没有找到解决方案，于是，我就决定自己去查看一下Emacs的url-http的源码：

c:/emacs/share/emacs/26.0.50/lisp/url/url-http.el.gz

然后，发现在第395行的位置，有这么一段代码：

;; Bug#23750
(unless (= (string-bytes request)
           (length request))
  (error "Multibyte text in HTTP request: %s" request))

无疑就是这个地方报的错，为什么会报错呢？

去看一下之前版本的代码就知道了，原来是没有这几行代码的，作者也标明了，加入这几行代码是为了解决 Bug#23750，而这个bug我也去查了一下，应该是json.el中的一个bug，也就是说，如果代码不在这个地方检查报错，后面如果要使用到json中的函数的话，同样也会报错，并且据介绍，会更加隐晦，更难查找（去搜索json中的中文问题）。所以，作者在这里提前报错。

那这个错误到底是什么呢？

就是说 (string-bytes request) 和 (length request) 的返回值不一样的时候，就会报错。而中文字符的string-bytes，如果用utf-8来进行编码的话，字符长度是变化的，中文的编码平均大概是每个字会占用3个bytes，而 length 函数返回的会是1。那结果当然是不相等，当然会报错了。

怎么解决呢？一个简单的方法是：

;; Bug#23750
(setq request (url-http--encode-string request))
(unless (= (string-bytes request)
           (length request))
  (error "Multibyte text in HTTP request: %s" request))

其中的 url-http--encode-string 也是作者新增的：

(defun url-http--encode-string (s)
  (if (multibyte-string-p s)
      (encode-coding-string s \'us-ascii)
    s))

把传进来的中文先转换为\'us-ascii编码，这样，两种函数返回值就是相等的了。当然，为什么可以这样，把中文转换为ascii，照理压根儿就不可行吧？这里没有想明白。但是可以工作了，是不是作用只是把这个判断跳过去了，后面使用json还是会报错？这个目前还没有去测试。但是，确实是可以工作了，我目前的这个文章就是使用这个来发布的。

完整的函数，把它添加到配置文件中去就可以了：

(defun url-http-create-request (&optional ref-url)
  "Create an HTTP request for `url-http-target-url\', referred to by REF-URL."
  (let* ((extra-headers)
         (request nil)
         (no-cache (cdr-safe (assoc "Pragma" url-http-extra-headers)))
         (using-proxy url-http-proxy)
         (proxy-auth (if (or (cdr-safe (assoc "Proxy-Authorization"
                                              url-http-extra-headers))
                             (not using-proxy))
                         nil
                       (let ((url-basic-auth-storage
                              \'url-http-proxy-basic-auth-storage))
                         (url-get-authentication url-http-proxy nil \'any nil))))
         (real-fname (url-filename url-http-target-url))
         (host (url-http--encode-string (url-host url-http-target-url)))
         (auth (if (cdr-safe (assoc "Authorization" url-http-extra-headers))
                   nil
                 (url-get-authentication (or
                                          (and (boundp \'proxy-info)
                                               proxy-info)
                                          url-http-target-url) nil \'any nil))))
    (if (equal "" real-fname)
        (setq real-fname "/"))
    (setq no-cache (and no-cache (string-match "no-cache" no-cache)))
    (if auth
        (setq auth (concat "Authorization: " auth "\\r\\n")))
    (if proxy-auth
        (setq proxy-auth (concat "Proxy-Authorization: " proxy-auth "\\r\\n")))

    ;; Protection against stupid values in the referrer
    (if (and ref-url (stringp ref-url) (or (string= ref-url "file:nil")
                                           (string= ref-url "")))
        (setq ref-url nil))

    ;; We do not want to expose the referrer if the user is paranoid.
    (if (or (memq url-privacy-level \'(low high paranoid))
            (and (listp url-privacy-level)
                 (memq \'lastloc url-privacy-level)))
        (setq ref-url nil))

    ;; url-http-extra-headers contains an assoc-list of
    ;; header/value pairs that we need to put into the request.
    (setq extra-headers (mapconcat
                         (lambda (x)
                           (concat (car x) ": " (cdr x)))
                         url-http-extra-headers "\\r\\n"))
    (if (not (equal extra-headers ""))
        (setq extra-headers (concat extra-headers "\\r\\n")))

    ;; This was done with a call to `format\'.  Concatenating parts has
    ;; the advantage of keeping the parts of each header together and
    ;; allows us to elide null lines directly, at the cost of making
    ;; the layout less clear.
    (setq request
          (concat
             ;; The request
             (or url-http-method "GET") " "
             (url-http--encode-string
              (if using-proxy (url-recreate-url url-http-target-url) real-fname))
             " HTTP/" url-http-version "\\r\\n"
             ;; Version of MIME we speak
             "MIME-Version: 1.0\\r\\n"
             ;; (maybe) Try to keep the connection open
             "Connection: " (if (or using-proxy
                                    (not url-http-attempt-keepalives))
                                "close" "keep-alive") "\\r\\n"
                                ;; HTTP extensions we support
             (if url-extensions-header
                 (format
                  "Extension: %s\\r\\n" url-extensions-header))
             ;; Who we want to talk to
             (if (/= (url-port url-http-target-url)
                     (url-scheme-get-property
                      (url-type url-http-target-url) \'default-port))
                 (format
                  "Host: %s:%d\\r\\n" (puny-encode-domain host)
                  (url-port url-http-target-url))
               (format "Host: %s\\r\\n" (puny-encode-domain host)))
             ;; Who its from
             (if url-personal-mail-address
                 (concat
                  "From: " url-personal-mail-address "\\r\\n"))
             ;; Encodings we understand
             (if (or url-mime-encoding-string
                     ;; MS-Windows loads zlib dynamically, so recheck
                     ;; in case they made it available since
                     ;; initialization in url-vars.el.
                     (and (eq \'system-type \'windows-nt)
                          (fboundp \'zlib-available-p)
                          (zlib-available-p)
                          (setq url-mime-encoding-string "gzip")))
                 (concat
                  "Accept-encoding: " url-mime-encoding-string "\\r\\n"))
             (if url-mime-charset-string
                 (concat
                  "Accept-charset: "
                  (url-http--encode-string url-mime-charset-string)
                  "\\r\\n"))
             ;; Languages we understand
             (if url-mime-language-string
                 (concat
                  "Accept-language: " url-mime-language-string "\\r\\n"))
             ;; Types we understand
             "Accept: " (or url-mime-accept-string "*/*") "\\r\\n"
             ;; User agent
             (url-http-user-agent-string)
             ;; Proxy Authorization
             proxy-auth
             ;; Authorization
             auth
             ;; Cookies
             (when (url-use-cookies url-http-target-url)
               (url-http--encode-string
                (url-cookie-generate-header-lines
                 host real-fname
                 (equal "https" (url-type url-http-target-url)))))
             ;; If-modified-since
             (if (and (not no-cache)
                      (member url-http-method \'("GET" nil)))
                 (let ((tm (url-is-cached url-http-target-url)))
                   (if tm
                       (concat "If-modified-since: "
                               (url-get-normalized-date tm) "\\r\\n"))))
             ;; Whence we came
             (if ref-url (concat
                          "Referer: " ref-url "\\r\\n"))
             extra-headers
             ;; Length of data
             (if url-http-data
                 (concat
                  "Content-length: " (number-to-string
                                      (length url-http-data))
                  "\\r\\n"))
             ;; End request
             "\\r\\n"
             ;; Any data
             url-http-data))
    ;; Bug#23750
    (setq request (url-http--encode-string request))
    (unless (= (string-bytes request)
               (length request))
      (error "Multibyte text in HTTP request: %s" request))
    (url-http-debug "Request is: \\n%s" request)
    request))