javascript - Peg.js 区分缺失值和空格

Question

我有以下 peg.js 脚本:

start = name* 

name = '** name ' var ws 'var:' vr:var ws 'len:' n:num? ws 'label:' lb:label? 'type:' ws t:type? '**\n'
  {return {NAME: vr,
           LENGTH: n, 
           LABEL:lb,
           TYPE: t
  }}

type = 'CHAR'/'NUM'    
var = $([a-zA-Z_][a-zA-Z0-9_]*)
label = p:labChar* { return p.join('')}
labChar = [^'"<>|\*\/]
ws = [\\t\\r ]
num  = n:[0-9]+ {return n.join('')}

解析:

** name a1 var:a1 len:9 label:The is the label for a1 type:NUM **
** name a2 var:a2 len: label:The is the label for a2 type:CHAR **
** name a3 var:a3 len:67 label: type: **

我遇到了几个问题。

首先，在我解析的文本中，我期望某些值标签，例如“var:”、“len:”、“label:”和“type:”。我想使用这些标签(我知道它们是固定的)来划分值。

其次，我需要允许缺失值。

我这样做的方式正确吗？目前我的脚本将标签的值与类型合并，然后我在以下位置收到错误:

Line 1, column 64: Expected "type:" or [^'"<>|*/] but "*" found.

此外，我也可以对文本 block 执行此操作吗？我试过解析:

** name a1 var:a1 len:9 label:The is the label for a1 type:NUM **
** name a2 var:a2 len: label:The is the label for a2 type:CHAR **

randomly created text ()= that I would like to keep

** name b1 var:b1 len:9 label:This is the label for b1 type:NUM **
** name b2 var:b2 len: label:This is the label for b2 type:CHAR **

more text 

通过修改第一行并添加以下内容:

start = (name/random)* 

random = r:.+ (!'** name')
    {return {RANDOM: r.join('')}}

我在寻找最终结果:

[
   [{
      "NAME": "a1",
      "LENGTH": "9",
      "LABEL": "The is the label for a1",
      "TYPE": "NUM"
   },
   {
      "NAME": "a2",
      "LENGTH": null,
      "LABEL": "The is the label for a2",
      "TYPE": "CHAR"
   },
   {"RANDOM":"randomly created text ()= that I would like to keep"}]
[{
      "NAME": "b1",
      "LENGTH": "9",
      "LABEL": "This is the label for b1",
      "TYPE": "NUM"
   },
   {
      "NAME": "b2",
      "LENGTH": null,
      "LABEL": "This is the label for b2",
      "TYPE": "CHAR"
   },
   {"RANDOM":"more text "}]
] 

Answer 1

你需要一个否定的先行 !(ws 'type:') 否则，标签规则将过于贪婪并消耗所有输入到行尾。

作为旁注，您可以使用 $() 语法来连接元素的文本，而不是 {return n.join('')}。

start = name*

name = '** name ' var ws 'var:' vr:var ws 'len:' n:num? ws 'label:' lb:label? ws 'type:' t:type? ws '**' '\n'?
  {return {NAME: vr,
           LENGTH: n, 
           LABEL:lb,
           TYPE: t
  }}

var = $([a-zA-Z_][a-zA-Z0-9_]*)

num  = $([0-9]+)

label = $((!(ws 'type:') [^'"<>|\*\/])*)

type = 'CHAR'/'NUM'

ws = [\\t\\r ]

输出:

[
   {
      "NAME": "a1",
      "LENGTH": "9",
      "LABEL": "The is the label for a1",
      "TYPE": "NUM"
   },
   {
      "NAME": "a2",
      "LENGTH": null,
      "LABEL": "The is the label for a2",
      "TYPE": "CHAR"
   },
   {
      "NAME": "a3",
      "LENGTH": "67",
      "LABEL": "",
      "TYPE": null
   }
]