Ripper

Class

Ripper is a Ruby script parser.

You can get information from the parser with event-based style. Information such as abstract syntax trees or simple lexical analysis of the Ruby program.

Usage

Ripper provides an easy interface for parsing your program into a symbolic expression tree (or S-expression).

Understanding the output of the parser may come as a challenge, it’s recommended you use PP to format the output for legibility.

require 'ripper'
require 'pp'

pp Ripper.sexp('def hello(world) "Hello, #{world}!"; end')
  #=> [:program,
       [[:def,
         [:@ident, "hello", [1, 4]],
         [:paren,
          [:params, [[:@ident, "world", [1, 10]]], nil, nil, nil, nil, nil, nil]],
         [:bodystmt,
          [[:string_literal,
            [:string_content,
             [:@tstring_content, "Hello, ", [1, 18]],
             [:string_embexpr, [[:var_ref, [:@ident, "world", [1, 27]]]]],
             [:@tstring_content, "!", [1, 33]]]]],
          nil,
          nil,
          nil]]]]

You can see in the example above, the expression starts with :program.

From here, a method definition at :def, followed by the method’s identifier :@ident. After the method’s identifier comes the parentheses :paren and the method parameters under :params.

Next is the method body, starting at :bodystmt (stmt meaning statement), which contains the full definition of the method.

In our case, we’re simply returning a String, so next we have the :string_literal expression.

Within our :string_literal you’ll notice two @tstring_content, this is the literal part for Hello, and !. Between the two @tstring_content statements is a :string_embexpr, where embexpr is an embedded expression. Our expression consists of a local variable, or var_ref, with the identifier (@ident) of world.

Resources

Ruby Inside

Requirements

ruby 1.9 (support CVS HEAD only)
bison 1.28 or later (Other yaccs do not work)

License

Ruby License.

Minero Aoki
aamine@loveruby.net
i.loveruby.net

Constants

PARSER_EVENTS

This array contains name of parser events.

SCANNER_EVENTS

This array contains name of scanner events.

EVENTS

This array contains name of all ripper events.

Version

version of Ripper

Class Methods

Ripper.dedent_string(input, width) → Integer

parse.c View on GitHub

          
            static VALUE
parser_dedent_string(VALUE self, VALUE input, VALUE width)
{
    int wid, col;

    StringValue(input);
    wid = NUM2UINT(width);
    col = dedent_string(input, wid);
    return INT2NUM(col);
}

USE OF RIPPER LIBRARY ONLY.

Strips up to width leading whitespaces from input, and returns the stripped column width.

lex(src, filename = '-', lineno = 1, **kw)

ext/ripper/lib/ripper/lexer.rb View on GitHub

          
            # File tmp/rubies/ruby-3.0.5/ext/ripper/lib/ripper/lexer.rb, line 51
def Ripper.lex(src, filename = '-', lineno = 1, **kw)
  Lexer.new(src, filename, lineno).lex(**kw)
end

Tokenizes the Ruby program and returns an array of an array, which is formatted like [[lineno, column], type, token, state]. The filename argument is mostly ignored. By default, this method does not handle syntax errors in src, use the raise_errors keyword to raise a SyntaxError for an error in src.

require 'ripper'
require 'pp'

pp Ripper.lex("def m(a) nil end")
#=> [[[1,  0], :on_kw,     "def", FNAME    ],
     [[1,  3], :on_sp,     " ",   FNAME    ],
     [[1,  4], :on_ident,  "m",   ENDFN    ],
     [[1,  5], :on_lparen, "(",   BEG|LABEL],
     [[1,  6], :on_ident,  "a",   ARG      ],
     [[1,  7], :on_rparen, ")",   ENDFN    ],
     [[1,  8], :on_sp,     " ",   BEG      ],
     [[1,  9], :on_kw,     "nil", END      ],
     [[1, 12], :on_sp,     " ",   END      ],
     [[1, 13], :on_kw,     "end", END      ]]

Ripper.lex_state_name(integer) → string

parse.c View on GitHub

          
            static VALUE
ripper_lex_state_name(VALUE self, VALUE state)
{
    return rb_parser_lex_state_name(NUM2INT(state));
}

Returns a string representation of lex_state.

Ripper.new(src, filename="(ripper)", lineno=1) → ripper

parse.c View on GitHub

          
            static VALUE
ripper_initialize(int argc, VALUE *argv, VALUE self)
{
    struct parser_params *p;
    VALUE src, fname, lineno;

    TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
    rb_scan_args(argc, argv, "12", &src, &fname, &lineno);
    if (RB_TYPE_P(src, T_FILE)) {
        p->lex.gets = ripper_lex_io_get;
    }
    else if (rb_respond_to(src, id_gets)) {
        p->lex.gets = ripper_lex_get_generic;
    }
    else {
        StringValue(src);
        p->lex.gets = lex_get_str;
    }
    p->lex.input = src;
    p->eofp = 0;
    if (NIL_P(fname)) {
        fname = STR_NEW2("(ripper)");
        OBJ_FREEZE(fname);
    }
    else {
        StringValueCStr(fname);
        fname = rb_str_new_frozen(fname);
    }
    parser_initialize(p);

    p->ruby_sourcefile_string = fname;
    p->ruby_sourcefile = RSTRING_PTR(fname);
    p->ruby_sourceline = NIL_P(lineno) ? 0 : NUM2INT(lineno) - 1;

    return Qnil;
}

Create a new Ripper object. src must be a String, an IO, or an Object which has gets method.

This method does not starts parsing. See also Ripper#parse and Ripper.parse.

parse(src, filename = '(ripper)', lineno = 1)

ext/ripper/lib/ripper/core.rb View on GitHub

          
            # File tmp/rubies/ruby-3.0.5/ext/ripper/lib/ripper/core.rb, line 18
def Ripper.parse(src, filename = '(ripper)', lineno = 1)
  new(src, filename, lineno).parse
end

Parses the given Ruby program read from src. src must be a String or an IO or a object with a gets method.

sexp(src, filename = '-', lineno = 1, raise_errors: false)

ext/ripper/lib/ripper/sexp.rb View on GitHub

          
            # File tmp/rubies/ruby-3.0.5/ext/ripper/lib/ripper/sexp.rb, line 35
def Ripper.sexp(src, filename = '-', lineno = 1, raise_errors: false)
  builder = SexpBuilderPP.new(src, filename, lineno)
  sexp = builder.parse
  if builder.error?
    if raise_errors
      raise SyntaxError, builder.error
    end
  else
    sexp
  end
end

EXPERIMENTAL

Parses src and create S-exp tree. Returns more readable tree rather than Ripper.sexp_raw. This method is mainly for developer use. The filename argument is mostly ignored. By default, this method does not handle syntax errors in src, returning nil in such cases. Use the raise_errors keyword to raise a SyntaxError for an error in src.

require 'ripper'
require 'pp'

pp Ripper.sexp("def m(a) nil end")
  #=> [:program,
       [[:def,
        [:@ident, "m", [1, 4]],
        [:paren, [:params, [[:@ident, "a", [1, 6]]], nil, nil, nil, nil, nil, nil]],
        [:bodystmt, [[:var_ref, [:@kw, "nil", [1, 9]]]], nil, nil, nil]]]]

sexp_raw(src, filename = '-', lineno = 1, raise_errors: false)

ext/ripper/lib/ripper/sexp.rb View on GitHub

          
            # File tmp/rubies/ruby-3.0.5/ext/ripper/lib/ripper/sexp.rb, line 71
def Ripper.sexp_raw(src, filename = '-', lineno = 1, raise_errors: false)
  builder = SexpBuilder.new(src, filename, lineno)
  sexp = builder.parse
  if builder.error?
    if raise_errors
      raise SyntaxError, builder.error
    end
  else
    sexp
  end
end

EXPERIMENTAL

Parses src and create S-exp tree. This method is mainly for developer use. The filename argument is mostly ignored. By default, this method does not handle syntax errors in src, returning nil in such cases. Use the raise_errors keyword to raise a SyntaxError for an error in src.

require 'ripper'
require 'pp'

pp Ripper.sexp_raw("def m(a) nil end")
  #=> [:program,
       [:stmts_add,
        [:stmts_new],
        [:def,
         [:@ident, "m", [1, 4]],
         [:paren, [:params, [[:@ident, "a", [1, 6]]], nil, nil, nil]],
         [:bodystmt,
          [:stmts_add, [:stmts_new], [:var_ref, [:@kw, "nil", [1, 9]]]],
          nil,
          nil,
          nil]]]]

slice(src, pattern, n = 0)

ext/ripper/lib/ripper/lexer.rb View on GitHub

          
            # File tmp/rubies/ruby-3.0.5/ext/ripper/lib/ripper/lexer.rb, line 224
def Ripper.slice(src, pattern, n = 0)
  if m = token_match(src, pattern)
  then m.string(n)
  else nil
  end
end

EXPERIMENTAL

Parses src and return a string which was matched to pattern. pattern should be described as Regexp.

require 'ripper'

p Ripper.slice('def m(a) nil end', 'ident')                   #=> "m"
p Ripper.slice('def m(a) nil end', '[ident lparen rparen]+')  #=> "m(a)"
p Ripper.slice("<<EOS\nstring\nEOS",
               'heredoc_beg nl $(tstring_content*) heredoc_end', 1)
    #=> "string\n"

tokenize(src, filename = '-', lineno = 1, **kw)

ext/ripper/lib/ripper/lexer.rb View on GitHub

          
            # File tmp/rubies/ruby-3.0.5/ext/ripper/lib/ripper/lexer.rb, line 25
def Ripper.tokenize(src, filename = '-', lineno = 1, **kw)
  Lexer.new(src, filename, lineno).tokenize(**kw)
end

Tokenizes the Ruby program and returns an array of strings. The filename and lineno arguments are mostly ignored, since the return value is just the tokenized input. By default, this method does not handle syntax errors in src, use the raise_errors keyword to raise a SyntaxError for an error in src.

p Ripper.tokenize("def m(a) nil end")
   # => ["def", " ", "m", "(", "a", ")", " ", "nil", " ", "end"]

Instance Methods

ripper.column → Integer

parse.c View on GitHub

          
            static VALUE
ripper_column(VALUE self)
{
    struct parser_params *p;
    long col;

    TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
    if (!ripper_initialized_p(p)) {
        rb_raise(rb_eArgError, "method called for uninitialized object");
    }
    if (NIL_P(p->parsing_thread)) return Qnil;
    col = p->lex.ptok - p->lex.pbeg;
    return LONG2NUM(col);
}

Return column number of current parsing line. This number starts from 0.

compile_error(msg)

ext/ripper/lib/ripper/core.rb View on GitHub

          
            # File tmp/rubies/ruby-3.0.5/ext/ripper/lib/ripper/core.rb, line 63
def compile_error(msg)
end

This method is called when the parser found syntax error.

ripper.debug_output → obj

parse.c View on GitHub

          
            VALUE
rb_parser_get_debug_output(VALUE self)
{
    struct parser_params *p;

    TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
    return p->debug_output;
}

Get debug output.

ripper.debug_output = obj

parse.c View on GitHub

          
            VALUE
rb_parser_set_debug_output(VALUE self, VALUE output)
{
    struct parser_params *p;

    TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
    return p->debug_output = output;
}

Set debug output.

Ripper.dedent_string(input, width) → Integer

parse.c View on GitHub

          
            static VALUE
parser_dedent_string(VALUE self, VALUE input, VALUE width)
{
    int wid, col;

    StringValue(input);
    wid = NUM2UINT(width);
    col = dedent_string(input, wid);
    return INT2NUM(col);
}

USE OF RIPPER LIBRARY ONLY.

Strips up to width leading whitespaces from input, and returns the stripped column width.

ripper.encoding → encoding

parse.c View on GitHub

          
            VALUE
rb_parser_encoding(VALUE vparser)
{
    struct parser_params *p;

    TypedData_Get_Struct(vparser, struct parser_params, &parser_data_type, p);
    return rb_enc_from_encoding(p->enc);
}

Return encoding of the source.

ripper.end_seen? → Boolean

parse.c View on GitHub

          
            VALUE
rb_parser_end_seen_p(VALUE vparser)
{
    struct parser_params *p;

    TypedData_Get_Struct(vparser, struct parser_params, &parser_data_type, p);
    return p->ruby__end__seen ? Qtrue : Qfalse;
}

Return true if parsed source ended by +_END_+.

ripper.error? → Boolean

parse.c View on GitHub

          
            static VALUE
ripper_error_p(VALUE vparser)
{
    struct parser_params *p;

    TypedData_Get_Struct(vparser, struct parser_params, &parser_data_type, p);
    return p->error_p ? Qtrue : Qfalse;
}

Return true if parsed source has errors.

ripper.filename → String

parse.c View on GitHub

          
            static VALUE
ripper_filename(VALUE self)
{
    struct parser_params *p;

    TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
    if (!ripper_initialized_p(p)) {
        rb_raise(rb_eArgError, "method called for uninitialized object");
    }
    return p->ruby_sourcefile_string;
}

Return current parsing filename.

ripper.lineno → Integer

parse.c View on GitHub

          
            static VALUE
ripper_lineno(VALUE self)
{
    struct parser_params *p;

    TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
    if (!ripper_initialized_p(p)) {
        rb_raise(rb_eArgError, "method called for uninitialized object");
    }
    if (NIL_P(p->parsing_thread)) return Qnil;
    return INT2NUM(p->ruby_sourceline);
}

Return line number of current parsing line. This number starts from 1.

ripper.parse

parse.c View on GitHub

          
            static VALUE
ripper_parse(VALUE self)
{
    struct parser_params *p;

    TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
    if (!ripper_initialized_p(p)) {
        rb_raise(rb_eArgError, "method called for uninitialized object");
    }
    if (!NIL_P(p->parsing_thread)) {
        if (p->parsing_thread == rb_thread_current())
            rb_raise(rb_eArgError, "Ripper#parse is not reentrant");
        else
            rb_raise(rb_eArgError, "Ripper#parse is not multithread-safe");
    }
    p->parsing_thread = rb_thread_current();
    rb_ensure(ripper_parse0, self, ripper_ensure, self);

    return p->result;
}

Start parsing and returns the value of the root action.

ripper.state → Integer

parse.c View on GitHub

          
            static VALUE
ripper_state(VALUE self)
{
    struct parser_params *p;

    TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
    if (!ripper_initialized_p(p)) {
        rb_raise(rb_eArgError, "method called for uninitialized object");
    }
    if (NIL_P(p->parsing_thread)) return Qnil;
    return INT2NUM(p->lex.state);
}

Return scanner state of current token.

ripper.token → String

parse.c View on GitHub

          
            static VALUE
ripper_token(VALUE self)
{
    struct parser_params *p;
    long pos, len;

    TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
    if (!ripper_initialized_p(p)) {
        rb_raise(rb_eArgError, "method called for uninitialized object");
    }
    if (NIL_P(p->parsing_thread)) return Qnil;
    pos = p->lex.ptok - p->lex.pbeg;
    len = p->lex.pcur - p->lex.ptok;
    return rb_str_subseq(p->lex.lastline, pos, len);
}

Return the current token string.

warn(fmt, *args)

ext/ripper/lib/ripper/core.rb View on GitHub

          
            # File tmp/rubies/ruby-3.0.5/ext/ripper/lib/ripper/core.rb, line 54
def warn(fmt, *args)
end

This method is called when weak warning is produced by the parser. fmt and args is printf style.

warning(fmt, *args)

ext/ripper/lib/ripper/core.rb View on GitHub

          
            # File tmp/rubies/ruby-3.0.5/ext/ripper/lib/ripper/core.rb, line 59
def warning(fmt, *args)
end

This method is called when strong warning is produced by the parser. fmt and args is printf style.

ripper.yydebug → true or false

parse.c View on GitHub

          
            VALUE
rb_parser_get_yydebug(VALUE self)
{
    struct parser_params *p;

    TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
    return p->debug ? Qtrue : Qfalse;
}

Get yydebug.

ripper.yydebug = flag

parse.c View on GitHub

          
            VALUE
rb_parser_set_yydebug(VALUE self, VALUE flag)
{
    struct parser_params *p;

    TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
    p->debug = RTEST(flag);
    return flag;
}

Set yydebug.