Emacs25.1之后UrlHttpError
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Emacs25.1之后UrlHttpError
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))