为什么ruby的JSON解析器会吃掉我的反斜杠？

问题描述

下面的JSON格式示例包含一个反斜杠，如果我运行 JSON.load ，反斜杠就会消失：

The following example in JSON format contains one backslash, and if I run JSON.load, the backslash disappears:

JSON.load('{ "88694": { "regex": ".*?\. (CVE-2015-46055)" } }')
# => {"88694"=>{ "regex"=>".*?. (CVE-2015-46055)"}}

如何保留反斜杠？

我的目标是拥有这种结构，并在需要时读取文件并加载JSON

My goal is to have this structure, and whenever I need, read the file, load the JSON into Hash, and search for those regular expressions.

UPDATE 1

这是我想要的一个示例。

here is an example what I want.

irb> "stack.overflow"[/.*?\./]
=> "stack."

我无法将正则表达式从JSON顺序传递给我的字符串赶上 。，因为 \。

I can't pass the regex from JSON to my string in order to catch that ".", because the "\." disappears.

推荐答案

str = '{ "88694": { "regex": ".*?\. (CVE-2015-46055)" } }'
  #=> "{ \"88694\": { \"regex\": \".*?\\. (CVE-2015-46055)\" } }"

str.chars
  #=> ["{", " ", "\"", "8", "8", "6", "9", "4", "\"", ":", " ", "{", " ",
  #   "\"", "r", "e", "g", "e", "x", "\"", ":", " ", "\"", ".", "*", "?",
  #   "\\", ".",
  #   ~~~   ~~                                        
  #   " ", "(",..., "}", " ", "}"]

我们发现 str 确实包含反斜杠字符和句点，原因是 str 用单引号引起来。 \。仅在 str 用双引号引起来时才视为转义期：

This shows us that str does indeed contain a backslash character followed by a period. The reason is that str is enclosed in single quotes. \. would only be treated as an escaped period if str were enclosed in double quotes:

 "{ '88694': { 'regex': '.*?\. (CVE-2015-46055)' } }".chars[25,3]
   #=> ["?", ".", " "] 

str 的返回值将单引号字符串转换为双引号字符串：

The return value of str converts the single-quoted string to a double-quoted string:

"{ \"88694\": { \"regex\": \".*?\\. (CVE-2015-46055)\" } }"

\\ 是一个反斜杠字符后跟一个句点。现在可以使用双引号将句号转义，但是它前面不能带有反斜杠，而只能带有一个退格字符。

\\ is one backslash character followed by a period. With the double quotes the period can now be escaped, but it is not preceded by a backslash, only by a backspace character.

现在让我们添加另一个反斜杠，看看会发生什么：

Now let's add another backslash and see what happens:

str1 = '{ "88694": { "regex": ".*?\\. (CVE-2015-46055)" } }' 
str1.chars == str.chars
  #=> true

结果相同。那是因为单引号支持转义序列 \\ （单反斜杠）（并且只有一个： \' [单引号]）。

The result is the same. That is because single quotes support the escape sequence \\ (single backslash) (and only one other: \' [single quote]).

现在让我们添加第三个反斜杠：

Now let's add a third backslash:

str2 = '{ "88694": { "regex": ".*?\\\. (CVE-2015-46055)" } }'   
str2.chars
  #=> ["{", " ", "\"", "8", "8", "6", "9", "4", "\"", ":", " ", "{", " ",
  #   "\"", "r", "e", "g", "e", "x", "\"", ":", " ", "\"", ".", "*", "?",
  #   "\\", "\\", ".",
  #   ~~~~  ~~~~  ~~~                                        
  #   " ", "(",..., "}", " ", "}"]

是否惊讶？ \\ 产生一个反斜杠字符（单引号中的转义反斜杠）， \ 产生第二个反斜杠字符（单引号中的反斜杠）和。是单引号中的句点。

Surprised? \\ produces one backslash character (escaped backslash in single quotes), \ products a second backslash character (backslash in single quotes) and . is a period in single quotes.

我们获得：

s = {"88694"=>{"regex"=>".*?\\. (CVE-2015-46055)"}.to_json

JSON.parse(str)
  #=> {"88694"=>{"regex"=>".*?. (CVE-2015-46055)"}} 
JSON.parse(str1)
  #=> {"88694"=>{"regex"=>".*?. (CVE-2015-46055)"}} 
JSON.parse(str2)
  #=> {"88694"=>{"regex"=>".*?\\. (CVE-2015-46055)"}} 

str2 是我们想要的，因为

JSON.parse(str2)["88694"]["regex"].chars[2,4]   
  #=> ["?", "\\", ".", " "] 

我们可以或者向后工作：

We could alternatively work backwards:

js = {"88694"=>{"regex"=>".*?\\. (CVE-2015-46055)"}}.to_json
  #=> "{\"88694\":{\"regex\":\".*?\\\\. (CVE-2015-46055)\"}}" 

'{"88694":{"regex":".*?\\\. (CVE-2015-46055)"}}' == js
  #=> true

此字符串与 str2 相同

似乎JSON将两个连续的反斜杠字符视为一个反斜杠字符。请参阅@Jordan的评论。

It appears that JSON treats two successive backslash characters as one backslash character. See @Jordan's comment.

也许读者可以在这里详细说明JSON在做什么。

Perhaps a reader can elaborate what JSON is doing here.

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