Issue #13686 has been updated by hsbt (Hiroshi SHIBATA).

Status changed from Open to Assigned
Assignee set to nobu (Nobuyoshi Nakada)
Target version set to 2.5

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Feature #13686: Add states of scanner to tokens from Ripper.lex and Ripper::Filter#on_*
https://bugs.ruby-lang.org/issues/13686#change-66351

* Author: aycabta (Code Ahss)
* Status: Assigned
* Priority: Normal
* Assignee: nobu (Nobuyoshi Nakada)
* Target version: 2.5
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I'm writing syntax analysis software by pure Ruby, for processing Ruby's source code and meta information what are classes, methods, constants, comments and others. I'm using Ripper for it. But the results of Ripper.sexp doesn't have comments, and the results of Ripper.lex doesn't have token states of scanner.

I think that the behavior of Ripper.sexp is correct because the position of comments in Ruby's syntax tree is blurred and unhandled.

On the other hand, Ripper.lex has comments token but Ripper.lex clearly drops the states of scanner for each tokens under "[finite-state scanner](https://ruby-hacking-guide.github.io/contextual.html)". The states are very important for many Ripper use cases. EXPR_END is especially required to know the end of statement. If the states aren't provided, we must re-implement finite-state analyzer for tokens from Ripper. For example, borderlines of conditions, args, constants and others. It's just not realistic.

In Ripper.lex's behavior as of now:

~~~ ruby
require 'ripper'
require 'pp'

pp Ripper.lex(<<EOM)
def str?(v)
  String === v # check
end
EOM
#=> [[[1,  0], :on_kw,         "def"      ],
#    [[1,  3], :on_sp,         " "        ],
#    [[1,  4], :on_ident,      "str?"     ],
#    [[1,  8], :on_lparen,     "("        ],
#    [[1,  9], :on_ident,      "v"        ],
#    [[1, 10], :on_rparen,     ")"        ],
#    [[1, 11], :on_ignored_nl, "\n"       ],
#    [[2,  0], :on_sp,         "  "       ],
#    [[2,  2], :on_const,      "String"   ],
#    [[2,  8], :on_sp,         " "        ],
#    [[2,  9], :on_op,         "==="      ],
#    [[2, 12], :on_sp,         " "        ],
#    [[2, 13], :on_ident,      "v"        ],
#    [[2, 14], :on_sp,         " "        ],
#    [[2, 15], :on_comment,    "# check\n"],
#    [[3,  0], :on_kw,         "end"      ],
#    [[3,  3], :on_nl,         "\n"       ]]
~~~

In Ripper.lex's behavior with attached patch:

~~~ ruby
require 'ripper'
require 'pp'

pp Ripper.lex(<<EOM)
def str?(v)
  String === v # check
end
EOM
#=> [[[1,  0], :on_kw,         "def",       Ripper::EXPR_FNAME                   ],
#    [[1,  3], :on_sp,         " ",         Ripper::EXPR_FNAME                   ],
#    [[1,  4], :on_ident,      "str?",      Ripper::EXPR_ENDFN                   ],
#    [[1,  8], :on_lparen,     "(",         Ripper::EXPR_BEG | Ripper::EXPR_LABEL],
#    [[1,  9], :on_ident,      "v",         Ripper::EXPR_ARG                     ],
#    [[1, 10], :on_rparen,     ")",         Ripper::EXPR_ENDFN                   ],
#    [[1, 11], :on_ignored_nl, "\n",        Ripper::EXPR_BEG                     ],
#    [[2,  0], :on_sp,         "  ",        Ripper::EXPR_BEG                     ],
#    [[2,  2], :on_const,      "String",    Ripper::EXPR_CMDARG                  ],
#    [[2,  8], :on_sp,         " ",         Ripper::EXPR_CMDARG                  ],
#    [[2,  9], :on_op,         "===",       Ripper::EXPR_BEG                     ],
#    [[2, 12], :on_sp,         " ",         Ripper::EXPR_BEG                     ],
#    [[2, 13], :on_ident,      "v",         Ripper::EXPR_END | Ripper::EXPR_LABEL],
#    [[2, 14], :on_sp,         " ",         Ripper::EXPR_END | Ripper::EXPR_LABEL],
#    [[2, 15], :on_comment,    "# check\n", Ripper::EXPR_END | Ripper::EXPR_LABEL],
#    [[3,  0], :on_kw,         "end",       Ripper::EXPR_END                     ],
#    [[3,  3], :on_nl,         "\n",        Ripper::EXPR_BEG                     ]]
~~~

In Ripper::Filter#on_* with attached patch, you can use #state metohd:

~~~ ruby
require 'ripper'
require 'pp'

class MyFilter < Ripper::Filter
  def on_default(event, tok, data)
    data.push([event, tok, state])
  end
end

# Ripper::Filter#parse works like Enumerable#inject
pp MyFilter.new(<<EOM).parse([])
def str?(v)
  String === v # check
end
EOM
#=> [[:on_kw,         "def",       Ripper::EXPR_FNAME                   ],
#    [:on_sp,         " ",         Ripper::EXPR_FNAME                   ],
#    [:on_ident,      "str?",      Ripper::EXPR_ENDFN                   ],
#    [:on_lparen,     "(",         Ripper::EXPR_BEG | Ripper::EXPR_LABEL],
#    [:on_ident,      "v",         Ripper::EXPR_ARG                     ],
#    [:on_rparen,     ")",         Ripper::EXPR_ENDFN                   ],
#    [:on_ignored_nl, "\n",        Ripper::EXPR_BEG                     ],
#    [:on_sp,         "  ",        Ripper::EXPR_BEG                     ],
#    [:on_const,      "String",    Ripper::EXPR_CMDARG                  ],
#    [:on_sp,         " ",         Ripper::EXPR_CMDARG                  ],
#    [:on_op,         "===",       Ripper::EXPR_BEG                     ],
#    [:on_sp,         " ",         Ripper::EXPR_BEG                     ],
#    [:on_ident,      "v",         Ripper::EXPR_END | Ripper::EXPR_LABEL],
#    [:on_sp,         " ",         Ripper::EXPR_END | Ripper::EXPR_LABEL],
#    [:on_comment,    "# check\n", Ripper::EXPR_END | Ripper::EXPR_LABEL],
#    [:on_kw,         "end",       Ripper::EXPR_END                     ],
#    [:on_nl,         "\n",        Ripper::EXPR_BEG                     ]]
~~~


---Files--------------------------------
add-state-to-ripper-for-trunk.patch (16.1 KB)


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