Support custom user defined declarative APIs

$.RULE("selectStatement", () => {
    $.SUBRULE($.selectClause)
    $.SUBRULE($.fromClause)
    $.OPTION(() => {
        $.SUBRULE($.whereClause)        
    })
})

rule('selectStatement', [{
    rule: 'selectClause',
  }, {
    rule: 'fromClause',
  }, {
    option: {rule: 'whereClause'}
  }      
])

$.RULE("selectClause", () => {
    $.CONSUME(Select);
    $.AT_LEAST_ONE_SEP({SEP: Comma, DEF: () => {
        $.CONSUME(Identifier);
    }});
})

$rule('selectClause', [{
    consume: Select
  }, {
    repeat: {
      min: 1,
      separator: Comma, 
      rule: {
        consume: Identifier
      }
    }
  }
])

[bd82]

btw, I understand the appeal of a “clearer natural API”.

But one of the reasoning for the existing ugly APIs is that by being “pure” programatic APIs with very little abstraction is that the parser can be easily debugged just by setting a regular break point inside the parser. No in any generated code or in any additional abstraction.

[bd82]

Usage Docs and links to runable example here: http://sap.github.io/chevrotain/website/Deep_Dive/custom_apis.html (link will be valid after 2.0 release.)