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Ripper Event structure

If you know about Ripper, you know that it’s a bridge between the ruby language parser and your own ruby app. It lets you parse ruby files just as ruby would see them. It’s currently marked as experimental, but its been in ruby since 1.9.

It’s quite hard going getting what you want out of it, one of the problems is the multiple arities of the events it produces. Another is its documentation, it’s really weak. Sven Fuchs wrote a pretty decent article to get you going.

In regards to the arities, you can discover the token<->event structure by firing up irb:

irb(main):001:0> require 'ripper.so' # To include the _TABLE constants
=> true
irb(main):002:0> require 'awesome_print' # for awesome output
=> true
irb(main):010:0> ap({ scanner: Ripper::SCANNER_EVENT_TABLE, parser: Ripper::PARSER_EVENT_TABLE })
{ :scanner => {
                 :CHAR => 1,
              :__end__ => 1,
              :backref => 1,
             :backtick => 1,
                :comma => 1,
              :comment => 1,
                :const => 1,
                 :cvar => 1,
               :embdoc => 1,
           :embdoc_beg => 1,
           :embdoc_end => 1,
          :embexpr_beg => 1,
          :embexpr_end => 1,
               :embvar => 1,
                :float => 1,
                 :gvar => 1,
          :heredoc_beg => 1,
          :heredoc_end => 1,
                :ident => 1,
           :ignored_nl => 1,
                  :int => 1,
                 :ivar => 1,
                   :kw => 1,
                :label => 1,
               :lbrace => 1,
             :lbracket => 1,
               :lparen => 1,
                   :nl => 1,
                   :op => 1,
               :period => 1,
         :qsymbols_beg => 1,
           :qwords_beg => 1,
               :rbrace => 1,
             :rbracket => 1,
           :regexp_beg => 1,
           :regexp_end => 1,
               :rparen => 1,
            :semicolon => 1,
                   :sp => 1,
               :symbeg => 1,
          :symbols_beg => 1,
              :tlambda => 1,
              :tlambeg => 1,
          :tstring_beg => 1,
      :tstring_content => 1,
          :tstring_end => 1,
            :words_beg => 1,
            :words_sep => 1},
:parser => {
                :BEGIN => 1,
                  :END => 1,
                :alias => 2,
          :alias_error => 1,
                 :aref => 2,
           :aref_field => 2,
        :arg_ambiguous => 0,
            :arg_paren => 1,
             :args_add => 2,
       :args_add_block => 2,
        :args_add_star => 2,
             :args_new => 0,
                :array => 1,
               :assign => 2,
         :assign_error => 1,
            :assoc_new => 2,
          :assoc_splat => 1,
  :assoclist_from_args => 1,
      :bare_assoc_hash => 1,
                :begin => 1,
               :binary => 3,
            :block_var => 2,
  :block_var_add_block => 2,
   :block_var_add_star => 2,
             :blockarg => 1,
             :bodystmt => 4,
          :brace_block => 2,
                :break => 1,
                 :call => 3,
                 :case => 2,
                :class => 3,
     :class_name_error => 1,
              :command => 2,
         :command_call => 4,
     :const_path_field => 2,
       :const_path_ref => 2,
            :const_ref => 1,
                  :def => 3,
              :defined => 1,
                 :defs => 5,
             :do_block => 2,
                 :dot2 => 2,
                 :dot3 => 2,
          :dyna_symbol => 1,
                 :else => 1,
                :elsif => 3,
               :ensure => 1,
       :excessed_comma => 1,
                :fcall => 1,
                :field => 3,
                  :for => 3,
                 :hash => 1,
                   :if => 3,
               :if_mod => 2,
                 :ifop => 3,
               :lambda => 2,
        :magic_comment => 2,
              :massign => 2,
       :method_add_arg => 2,
     :method_add_block => 2,
             :mlhs_add => 2,
        :mlhs_add_star => 2,
             :mlhs_new => 0,
           :mlhs_paren => 1,
               :module => 2,
             :mrhs_add => 2,
        :mrhs_add_star => 2,
             :mrhs_new => 0,
   :mrhs_new_from_args => 1,
                 :next => 1,
             :opassign => 3,
   :operator_ambiguous => 2,
          :param_error => 1,
               :params => 7,
                :paren => 1,
          :parse_error => 1,
              :program => 1,
         :qsymbols_add => 2,
         :qsymbols_new => 0,
           :qwords_add => 2,
           :qwords_new => 0,
                 :redo => 0,
           :regexp_add => 2,
       :regexp_literal => 2,
           :regexp_new => 0,
               :rescue => 4,
           :rescue_mod => 2,
           :rest_param => 1,
                :retry => 0,
               :return => 1,
              :return0 => 0,
               :sclass => 2,
            :stmts_add => 2,
            :stmts_new => 0,
           :string_add => 2,
        :string_concat => 2,
       :string_content => 0,
          :string_dvar => 1,
       :string_embexpr => 1,
       :string_literal => 1,
                :super => 1,
               :symbol => 1,
       :symbol_literal => 1,
          :symbols_add => 2,
          :symbols_new => 0,
      :top_const_field => 1,
        :top_const_ref => 1,
                :unary => 2,
                :undef => 1,
               :unless => 3,
           :unless_mod => 2,
                :until => 2,
            :until_mod => 2,
            :var_alias => 2,
            :var_field => 1,
              :var_ref => 1,
                :vcall => 1,
            :void_stmt => 0,
                 :when => 3,
                :while => 2,
            :while_mod => 2,
             :word_add => 2,
             :word_new => 0,
            :words_add => 2,
            :words_new => 0,
          :xstring_add => 2,
      :xstring_literal => 1,
          :xstring_new => 0,
                :yield => 1,
               :yield0 => 0,
               :zsuper => 0}}
=> nil

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