peggy

peggyjs/peggy
- PEG.js 后继
参考
PEG.js 之后新功能
- Global Initializers {{}}
  - 全局
  - {} 初始化是每次 parse 都会创建 - 能访问 options
- value plucking @
- typescript
- source maps
options
- grammarSource
- startRule

bash

npx -y peggy ./parser.pegjs --format es

flag	for
`--allowed-start-rules <rules>`	默认第一个,逗号分隔指定多个,`*` for all
`--ast`	输出内部 AST 代替 parser 源码
`--cache`	缓存结果,避免指数级解析时间,但解析会更慢
`-d, --dependency <[name:]module>`	依赖
`-D, --dependencies <json>`	依赖
`--dts`	生成 .d.ts 文件
`-e, --export-var <variable>`	全局变量
`--extra-options <options>`	额外选项 for peg.generate, json object
`-c, --extra-options-file <file>`	额外选项
`--format <format>`	输出格式, amd, commonjs, globals, umd, es
`-o, --output <file>`	输出文件
`--plugin`	插件
`-m, --source-map <file>`	生成 source map
`--return-types <JSON object>`	返回类型, for `--dts`
`-S, --start-rule <rule>`	指定 start rule
`-t, --test <text>`	测试
`-T, --test-file <text>`	测试
`--trace`	追踪
`-w,--watch`	监听

config.cjs

module.exports = {
  allowedStartRules = ["foo", "bar"],
  format: "umd",
  exportVar: "foo",
  input: "fooGrammar.peggy",
  plugins: [require("./plugin.js")],
  testFile: "myTestInput.foo",
  trace: true,
};

plugin.ts

export function use(config:{parser:Parser,reservedWords,passes:{ [stage: string]: Pass[] } }, options) => {
}

JavaScript

import peggy from 'peggy';
const parser = peggy.generate("start = ('a' / 'b')+");

const parser = peggy.generate([
  { source: 'file1.peggy', text: "numbers = number|.., ','|" },
  { source: 'lib.peggy', text: 'number = n:$[0-9]+ { return parseInt(n, 10) }' },
]);

syntax	for
`"a"`,`'a'`	匹配 a
`'a'i`	匹配 a 或 A
.	匹配任意
`!.`	EOF, EOI, End of Input
`[ab]`	匹配 a 或 b
`<rule>`	匹配 rule
`(expr)`	分组
`expr *`,`expr +`,`expr ?`	重复
`& expr`	positive assertion, lookahead
`! expr`	negative assertion, lookahead
`& { predicate }`	code block
`! { predicate }`	code block
`$ expr`	-> `{return text();}` - 语法糖
`label: expr`	定义 label/变量
`@(label:)? expr`	返回 label 作为内容 - pluck
`expr1 expr2`	顺序匹配
`expr { action }`	执行脚本
`expr1 / expr2`	alternate , choose
`expr \|COUNT\|`
`expr \|COUNT,SEQ\|`
`expr \|MIN..MAX\|`
`expr \|MIN..MAX,SEP\|`
`expr \|..\|`	-> `expr*`
`expr \|0..\|`	-> `expr*`
`expr \|1..\|`	-> `expr+`
`expr \|..1\|`	-> `expr?`

text

// use runtime value as option
start = count:n1 "a"|count|;
n1 = n:$[0-9] { return parseInt(n); };

start = "a"|{ return options.count; }|;

min,max,count 可以是 label/变量/code block

text

start = "a"|{ return options.count; }|;

text

// 手写
Values = next:(a:Value _ b:(_ ',' _ next:Value {return next})* ','? {return b?[a,...b]:a})? {return next || []}
// repeat
Values = next:(Value|..,","|)  ','?  {return next || []}

peggyjs/peggy/lib/peg.d.ts

Action Execution Environment

() 会形成变量作用域
input - parse 参数
options - parse 参数
error(message,where=location()) - 返回错误
expected(message, where=location())
location() - {source:options.grammarSource,start:{offset,line,column},end}
range() 只返回 offset 对象
offset() -> location().start.offset
text()
reserved/保留关键词
- count

text

{{
  // 全局初始化 - 定义的方法和变量全局有效
}}

{
  // parser 初始化
}

list = head:word tail:(_ "," _ @word)* { return [head, ...tail]; }
word = $[a-z]i+
_ = [ \t]*
__ "whitespace" // human-readable name
  = [ \t]+

text

// 引入另外的 rule
import {number} from "./number.js"
a = number|1.., "," WS|
WS = [ \t]*

text

list
  = word|.., delimiter| delimiter?
delimiter
  = _ "," _
word
  = $[a-z]i+
_
  = [ \t]*

Action Execution Environment

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参考资料