Class: Rouge::RegexLexer Abstract

Inherits:
Lexer
  • Object
show all
Defined in:
lib/rouge/regex_lexer.rb

Overview

This class is abstract.

A stateful lexer that uses sets of regular expressions to tokenize a string. Most lexers are instances of RegexLexer.

Direct Known Subclasses

Lexers::ABAP, Lexers::Actionscript, Lexers::Apache, Lexers::AppleScript, Lexers::Awk, Lexers::Bsl, Lexers::C, Lexers::CMake, Lexers::CSS, Lexers::CSharp, Lexers::Ceylon, Lexers::Cfscript, Lexers::Clojure, Lexers::Coffeescript, Lexers::CommonLisp, Lexers::Conf, Lexers::Coq, Lexers::D, Lexers::Dart, Lexers::Diff, Lexers::Docker, Lexers::Dot, Lexers::Eiffel, Lexers::Elixir, Lexers::Erlang, Lexers::FSharp, Lexers::Factor, Lexers::Fortran, Lexers::Gherkin, Lexers::Go, Lexers::GraphQL, Lexers::Groovy, Lexers::HTML, Lexers::HTTP, Lexers::Haml, Lexers::Haskell, Lexers::HyLang, Lexers::IDLang, Lexers::INI, Lexers::IO, Lexers::IgorPro, Lexers::JSON, Lexers::Java, Lexers::Javascript, Lexers::Jsonnet, Lexers::Julia, Lexers::Kotlin, Lexers::LLVM, Lexers::Liquid, Lexers::LiterateCoffeescript, Lexers::LiterateHaskell, Lexers::Lua, Lexers::MXML, Lexers::Make, Lexers::Markdown, Lexers::Matlab, Lexers::Moonscript, Lexers::Mosel, Lexers::Nasm, Lexers::Nginx, Lexers::Nim, Lexers::Nix, Lexers::OCaml, Lexers::Pascal, Lexers::Perl, Lexers::Plist, Lexers::Pony, Lexers::Praat, Lexers::Prolog, Lexers::Prometheus, Lexers::Properties, Lexers::Protobuf, Lexers::Puppet, Lexers::Python, Lexers::Q, Lexers::R, Lexers::Racket, Lexers::Ruby, Lexers::Rust, Lexers::SML, Lexers::SQL, Lexers::SassCommon, Lexers::Scala, Lexers::Scheme, Lexers::Sed, Lexers::Sed::Regex, Lexers::Sed::Replacement, Lexers::Shell, Lexers::Sieve, Lexers::Slim, Lexers::Smalltalk, Lexers::Swift, Lexers::TCL, Lexers::TOML, Lexers::Tap, Lexers::TeX, Lexers::Tulip, Lexers::Turtle, Lexers::VHDL, Lexers::Vala, Lexers::Verilog, Lexers::VimL, Lexers::VisualBasic, Lexers::Wollok, Lexers::XML, Lexers::YAML, TemplateLexer

Defined Under Namespace

Classes: Rule, State, StateDSL

Constant Summary collapse

MAX_NULL_SCANS =

The number of successive scans permitted without consuming the input stream. If this is exceeded, the match fails.

5

Constants included from Token::Tokens

Token::Tokens::Num, Token::Tokens::Str

Instance Attribute Summary

Attributes inherited from Lexer

#options

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Lexer

aliases, all, analyze_text, #as_bool, #as_lexer, #as_list, #as_string, #as_token, assert_utf8!, #bool_option, debug_enabled?, demo, demo_file, desc, disable_debug!, enable_debug!, filenames, find, find_fancy, guess, guess_by_filename, guess_by_mimetype, guess_by_source, guesses, #hash_option, #initialize, #lex, lex, #lexer_option, #list_option, mimetypes, option, option_docs, #string_option, #tag, tag, title, #token_option

Methods included from Token::Tokens

token

Constructor Details

This class inherits a constructor from Rouge::Lexer

Class Method Details

.append(name, &b) ⇒ Object


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# File 'lib/rouge/regex_lexer.rb', line 195

def self.append(name, &b)
  name = name.to_s
  dsl = state_definitions[name] or raise "no such state #{name.inspect}"
  replace_state(name, dsl.appended(&b))
end

.get_state(name) ⇒ Object


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# File 'lib/rouge/regex_lexer.rb', line 202

def self.get_state(name)
  return name if name.is_a? State

  states[name.to_sym] ||= begin
    defn = state_definitions[name.to_s] or raise "unknown state: #{name.inspect}"
    defn.to_state(self)
  end
end

.prepend(name, &b) ⇒ Object


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# File 'lib/rouge/regex_lexer.rb', line 189

def self.prepend(name, &b)
  name = name.to_s
  dsl = state_definitions[name] or raise "no such state #{name.inspect}"
  replace_state(name, dsl.prepended(&b))
end

.replace_state(name, new_defn) ⇒ Object


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# File 'lib/rouge/regex_lexer.rb', line 162

def self.replace_state(name, new_defn)
  states[name] = nil
  state_definitions[name] = new_defn
end

.start(&b) ⇒ Object

Specify an action to be run every fresh lex.

Examples:

start { puts "I'm lexing a new string!" }

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# File 'lib/rouge/regex_lexer.rb', line 178

def self.start(&b)
  start_procs << b
end

.start_procsObject

The routines to run at the beginning of a fresh lex.

See Also:


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# File 'lib/rouge/regex_lexer.rb', line 169

def self.start_procs
  @start_procs ||= InheritableList.new(superclass.start_procs)
end

.state(name, &b) ⇒ Object

Define a new state for this lexer with the given name. The block will be evaluated in the context of a StateDSL.


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# File 'lib/rouge/regex_lexer.rb', line 184

def self.state(name, &b)
  name = name.to_s
  state_definitions[name] = StateDSL.new(name, &b)
end

.state_definitionsObject


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# File 'lib/rouge/regex_lexer.rb', line 157

def self.state_definitions
  @state_definitions ||= InheritableHash.new(superclass.state_definitions)
end

.statesObject

The states hash for this lexer.

See Also:


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# File 'lib/rouge/regex_lexer.rb', line 153

def self.states
  @states ||= {}
end

Instance Method Details

#delegate(lexer, text = nil) ⇒ Object

Delegate the lex to another lexer. The #lex method will be called with `:continue` set to true, so that #reset! will not be called. In this way, a single lexer can be repeatedly delegated to while maintaining its own internal state stack.

Parameters:

  • lexer (#lex)

    The lexer or lexer class to delegate to

  • text (String) (defaults to: nil)

    The text to delegate. This defaults to the last matched string.


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# File 'lib/rouge/regex_lexer.rb', line 363

def delegate(lexer, text=nil)
  puts "    delegating to #{lexer.inspect}" if @debug
  text ||= @current_stream[0]

  lexer.lex(text, :continue => true) do |tok, val|
    puts "    delegated token: #{tok.inspect}, #{val.inspect}" if @debug
    yield_token(tok, val)
  end
end

#get_state(state_name) ⇒ Object


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# File 'lib/rouge/regex_lexer.rb', line 212

def get_state(state_name)
  self.class.get_state(state_name)
end

#goto(state_name) ⇒ Object

replace the head of the stack with the given state


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# File 'lib/rouge/regex_lexer.rb', line 407

def goto(state_name)
  raise 'empty stack!' if stack.empty?

  puts "    going to state :#{state_name} " if @debug
  stack[-1] = get_state(state_name)
end

#group(tok) ⇒ Object

Deprecated.

Yield a token with the next matched group. Subsequent calls to this method will yield subsequent groups.


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# File 'lib/rouge/regex_lexer.rb', line 342

def group(tok)
  raise "RegexLexer#group is deprecated: use #groups instead"
end

#groups(*tokens) ⇒ Object

Yield tokens corresponding to the matched groups of the current match.


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# File 'lib/rouge/regex_lexer.rb', line 348

def groups(*tokens)
  tokens.each_with_index do |tok, i|
    yield_token(tok, @current_stream[i+1])
  end
end

#in_state?(state_name) ⇒ Boolean

Check if `state_name` is in the state stack.

Returns:

  • (Boolean)

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# File 'lib/rouge/regex_lexer.rb', line 422

def in_state?(state_name)
  state_name = state_name.to_s
  stack.any? do |state|
    state.name == state_name.to_s
  end
end

#pop!(times = 1) ⇒ Object

Pop the state stack. If a number is passed in, it will be popped that number of times.


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# File 'lib/rouge/regex_lexer.rb', line 396

def pop!(times=1)
  raise 'empty stack!' if stack.empty?

  puts "    popping stack: #{times}" if @debug

  stack.pop(times)

  nil
end

#push(state_name = nil, &b) ⇒ Object

Push a state onto the stack. If no state name is given and you've passed a block, a state will be dynamically created using the StateDSL.


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# File 'lib/rouge/regex_lexer.rb', line 380

def push(state_name=nil, &b)
  push_state = if state_name
    get_state(state_name)
  elsif block_given?
    StateDSL.new(b.inspect, &b).to_state(self.class)
  else
    # use the top of the stack by default
    self.state
  end

  puts "    pushing :#{push_state.name}" if @debug
  stack.push(push_state)
end

#recurse(text = nil) ⇒ Object


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# File 'lib/rouge/regex_lexer.rb', line 373

def recurse(text=nil)
  delegate(self.class, text)
end

#reset!Object

reset this lexer to its initial state. This runs all of the start_procs.


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# File 'lib/rouge/regex_lexer.rb', line 233

def reset!
  @stack = nil
  @current_stream = nil

  puts "start blocks" if @debug && self.class.start_procs.any?
  self.class.start_procs.each do |pr|
    instance_eval(&pr)
  end
end

#reset_stackObject

reset the stack back to `[:root]`.


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# File 'lib/rouge/regex_lexer.rb', line 415

def reset_stack
  puts '    resetting stack' if @debug
  stack.clear
  stack.push get_state(:root)
end

#stackObject

The state stack. This is initially the single state `[:root]`. It is an error for this stack to be empty.

See Also:


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# File 'lib/rouge/regex_lexer.rb', line 219

def stack
  @stack ||= [get_state(:root)]
end

#stateObject

The current state - i.e. one on top of the state stack.

NB: if the state stack is empty, this will throw an error rather than returning nil.


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# File 'lib/rouge/regex_lexer.rb', line 227

def state
  stack.last or raise 'empty stack!'
end

#state?(state_name) ⇒ Boolean

Check if `state_name` is the state on top of the state stack.

Returns:

  • (Boolean)

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# File 'lib/rouge/regex_lexer.rb', line 430

def state?(state_name)
  state_name.to_s == state.name
end

#step(state, stream) ⇒ Object

Runs one step of the lex. Rules in the current state are tried until one matches, at which point its callback is called.

Returns:

  • true if a rule was tried successfully

  • false otherwise.


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# File 'lib/rouge/regex_lexer.rb', line 288

def step(state, stream)
  state.rules.each do |rule|
    if rule.is_a?(State)
      puts "  entering mixin #{rule.name}" if @debug
      return true if step(rule, stream)
      puts "  exiting  mixin #{rule.name}" if @debug
    else
      puts "  trying #{rule.inspect}" if @debug

      # XXX HACK XXX
      # StringScanner's implementation of ^ is b0rken.
      # see http://bugs.ruby-lang.org/issues/7092
      # TODO: this doesn't cover cases like /(a|^b)/, but it's
      # the most common, for now...
      next if rule.beginning_of_line && !stream.beginning_of_line?

      if (size = stream.skip(rule.re))
        puts "    got #{stream[0].inspect}" if @debug

        instance_exec(stream, &rule.callback)

        if size.zero?
          @null_steps += 1
          if @null_steps > MAX_NULL_SCANS
            puts "    too many scans without consuming the string!" if @debug
            return false
          end
        else
          @null_steps = 0
        end

        return true
      end
    end
  end

  false
end

#stream_tokens(str, &b) ⇒ Object

This implements the lexer protocol, by yielding [token, value] pairs.

The process for lexing works as follows, until the stream is empty:

  1. We look at the state on top of the stack (which by default is `[:root]`).

  2. Each rule in that state is tried until one is successful. If one is found, that rule's callback is evaluated - which may yield tokens and manipulate the state stack. Otherwise, one character is consumed with an `'Error'` token, and we continue at (1.)


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# File 'lib/rouge/regex_lexer.rb', line 255

def stream_tokens(str, &b)
  stream = StringScanner.new(str)

  @current_stream = stream
  @output_stream  = b
  @states         = self.class.states
  @null_steps     = 0

  until stream.eos?
    if @debug
      puts "lexer: #{self.class.tag}"
      puts "stack: #{stack.map(&:name).map(&:to_sym).inspect}"
      puts "stream: #{stream.peek(20).inspect}"
    end

    success = step(state, stream)

    if !success
      puts "    no match, yielding Error" if @debug
      b.call(Token::Tokens::Error, stream.getch)
    end
  end
end

#token(tok, val = @current_stream[0]) ⇒ Object

Yield a token.

Parameters:

  • tok

    the token type

  • val (defaults to: @current_stream[0])

    (optional) the string value to yield. If absent, this defaults to the entire last match.


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# File 'lib/rouge/regex_lexer.rb', line 334

def token(tok, val=@current_stream[0])
  yield_token(tok, val)
end