/
lexer.rb
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/
lexer.rb
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# -*- coding: utf-8 -*- #
# frozen_string_literal: true
# stdlib
require 'strscan'
require 'cgi'
require 'set'
module Rouge
# @abstract
# A lexer transforms text into a stream of `[token, chunk]` pairs.
class Lexer
include Token::Tokens
@option_docs = {}
class << self
# Lexes `stream` with the given options. The lex is delegated to a
# new instance.
#
# @see #lex
def lex(stream, opts={}, &b)
new(opts).lex(stream, &b)
end
# In case #continue_lex is called statically, we simply
# begin a new lex from the beginning, since there is no state.
#
# @see #continue_lex
def continue_lex(*a, &b)
lex(*a, &b)
end
# Given a name in string, return the correct lexer class.
# @param [String] name
# @return [Class<Rouge::Lexer>,nil]
def find(name)
registry[name.to_s]
end
# Same as ::find_fancy, except instead of returning an instantiated
# lexer, returns a pair of [lexer_class, options], so that you can
# modify or provide additional options to the lexer.
#
# Please note: the lexer class might be nil!
def lookup_fancy(str, code=nil, default_options={})
if str && !str.include?('?') && str != 'guess'
lexer_class = find(str)
return [lexer_class, default_options]
end
name, opts = str ? str.split('?', 2) : [nil, '']
# parse the options hash from a cgi-style string
opts = CGI.parse(opts || '').map do |k, vals|
val = case vals.size
when 0 then true
when 1 then vals[0]
else vals
end
[ k.to_s, val ]
end
opts = default_options.merge(Hash[opts])
lexer_class = case name
when 'guess', nil
self.guess(:source => code, :mimetype => opts['mimetype'])
when String
self.find(name)
end
[lexer_class, opts]
end
# Find a lexer, with fancy shiny features.
#
# * The string you pass can include CGI-style options
#
# Lexer.find_fancy('erb?parent=tex')
#
# * You can pass the special name 'guess' so we guess for you,
# and you can pass a second argument of the code to guess by
#
# Lexer.find_fancy('guess', "#!/bin/bash\necho Hello, world")
#
# If the code matches more than one lexer then Guesser::Ambiguous
# is raised.
#
# This is used in the Redcarpet plugin as well as Rouge's own
# markdown lexer for highlighting internal code blocks.
#
def find_fancy(str, code=nil, default_options={})
lexer_class, opts = lookup_fancy(str, code, default_options)
lexer_class && lexer_class.new(opts)
end
# Specify or get this lexer's title. Meant to be human-readable.
def title(t=nil)
if t.nil?
t = tag.capitalize
end
@title ||= t
end
# Specify or get this lexer's description.
def desc(arg=:absent)
if arg == :absent
@desc
else
@desc = arg
end
end
def option_docs
@option_docs ||= InheritableHash.new(superclass.option_docs)
end
def option(name, desc)
option_docs[name.to_s] = desc
end
# Specify or get the path name containing a small demo for
# this lexer (can be overriden by {demo}).
def demo_file(arg=:absent)
return @demo_file = Pathname.new(arg) unless arg == :absent
@demo_file = Pathname.new(File.join(__dir__, 'demos', tag))
end
# Specify or get a small demo string for this lexer
def demo(arg=:absent)
return @demo = arg unless arg == :absent
@demo = File.read(demo_file, mode: 'rt:bom|utf-8')
end
# @return a list of all lexers.
def all
@all ||= registry.values.uniq
end
# Guess which lexer to use based on a hash of info.
#
# This accepts the same arguments as Lexer.guess, but will never throw
# an error. It will return a (possibly empty) list of potential lexers
# to use.
def guesses(info={})
mimetype, filename, source = info.values_at(:mimetype, :filename, :source)
custom_globs = info[:custom_globs]
guessers = (info[:guessers] || []).dup
guessers << Guessers::Mimetype.new(mimetype) if mimetype
guessers << Guessers::GlobMapping.by_pairs(custom_globs, filename) if custom_globs && filename
guessers << Guessers::Filename.new(filename) if filename
guessers << Guessers::Modeline.new(source) if source
guessers << Guessers::Source.new(source) if source
guessers << Guessers::Disambiguation.new(filename, source) if source && filename
Guesser.guess(guessers, Lexer.all)
end
# Guess which lexer to use based on a hash of info.
#
# @option info :mimetype
# A mimetype to guess by
# @option info :filename
# A filename to guess by
# @option info :source
# The source itself, which, if guessing by mimetype or filename
# fails, will be searched for shebangs, <!DOCTYPE ...> tags, and
# other hints.
# @param [Proc] fallback called if multiple lexers are detected.
# If omitted, Guesser::Ambiguous is raised.
#
# @see Lexer.detect?
# @see Lexer.guesses
# @return [Class<Rouge::Lexer>]
def guess(info={}, &fallback)
lexers = guesses(info)
return Lexers::PlainText if lexers.empty?
return lexers[0] if lexers.size == 1
if fallback
fallback.call(lexers)
else
raise Guesser::Ambiguous.new(lexers)
end
end
def guess_by_mimetype(mt)
guess :mimetype => mt
end
def guess_by_filename(fname)
guess :filename => fname
end
def guess_by_source(source)
guess :source => source
end
def enable_debug!
@debug_enabled = true
end
def disable_debug!
remove_instance_variable :@debug_enabled if defined? @debug_enabled
end
def debug_enabled?
(defined? @debug_enabled) ? true : false
end
# Determine if a lexer has a method named +:detect?+ defined in its
# singleton class.
def detectable?
return @detectable if defined?(@detectable)
@detectable = singleton_methods(false).include?(:detect?)
end
protected
# @private
def register(name, lexer)
# reset an existing list of lexers
@all = nil if defined?(@all)
registry[name.to_s] = lexer
end
public
# Used to specify or get the canonical name of this lexer class.
#
# @example
# class MyLexer < Lexer
# tag 'foo'
# end
#
# MyLexer.tag # => 'foo'
#
# Lexer.find('foo') # => MyLexer
def tag(t=nil)
return @tag if t.nil?
@tag = t.to_s
Lexer.register(@tag, self)
end
# Used to specify alternate names this lexer class may be found by.
#
# @example
# class Erb < Lexer
# tag 'erb'
# aliases 'eruby', 'rhtml'
# end
#
# Lexer.find('eruby') # => Erb
def aliases(*args)
args.map!(&:to_s)
args.each { |arg| Lexer.register(arg, self) }
(@aliases ||= []).concat(args)
end
# Specify a list of filename globs associated with this lexer.
#
# If a filename glob is associated with more than one lexer, this can
# cause a Guesser::Ambiguous error to be raised in various guessing
# methods. These errors can be avoided by disambiguation. Filename globs
# are disambiguated in one of two ways. Either the lexer will define a
# `self.detect?` method (intended for use with shebangs and doctypes) or a
# manual rule will be specified in Guessers::Disambiguation.
#
# @example
# class Ruby < Lexer
# filenames '*.rb', '*.ruby', 'Gemfile', 'Rakefile'
# end
def filenames(*fnames)
(@filenames ||= []).concat(fnames)
end
# Specify a list of mimetypes associated with this lexer.
#
# @example
# class Html < Lexer
# mimetypes 'text/html', 'application/xhtml+xml'
# end
def mimetypes(*mts)
(@mimetypes ||= []).concat(mts)
end
# @private
def assert_utf8!(str)
encoding = str.encoding
return if encoding == Encoding::US_ASCII || encoding == Encoding::UTF_8 || encoding == Encoding::BINARY
raise EncodingError.new(
"Bad encoding: #{str.encoding.names.join(',')}. " +
"Please convert your string to UTF-8."
)
end
private
def registry
@registry ||= {}
end
end
# -*- instance methods -*- #
attr_reader :options
# Create a new lexer with the given options. Individual lexers may
# specify extra options. The only current globally accepted option
# is `:debug`.
#
# @option opts :debug
# Prints debug information to stdout. The particular info depends
# on the lexer in question. In regex lexers, this will log the
# state stack at the beginning of each step, along with each regex
# tried and each stream consumed. Try it, it's pretty useful.
def initialize(opts={})
@options = {}
opts.each { |k, v| @options[k.to_s] = v }
@debug = Lexer.debug_enabled? && bool_option('debug')
end
# Returns a new lexer with the given options set. Useful for e.g. setting
# debug flags post hoc, or providing global overrides for certain options
def with(opts={})
new_options = @options.dup
opts.each { |k, v| new_options[k.to_s] = v }
self.class.new(new_options)
end
def as_bool(val)
case val
when nil, false, 0, '0', 'false', 'off'
false
when Array
val.empty? ? true : as_bool(val.last)
else
true
end
end
def as_string(val)
return as_string(val.last) if val.is_a?(Array)
val ? val.to_s : nil
end
def as_list(val)
case val
when Array
val.flat_map { |v| as_list(v) }
when String
val.split(',')
else
[]
end
end
def as_lexer(val)
return as_lexer(val.last) if val.is_a?(Array)
return val.new(@options) if val.is_a?(Class) && val < Lexer
case val
when Lexer
val
when String
lexer_class = Lexer.find(val)
lexer_class && lexer_class.new(@options)
end
end
def as_token(val)
return as_token(val.last) if val.is_a?(Array)
case val
when Token
val
else
Token[val]
end
end
def bool_option(name, &default)
name_str = name.to_s
if @options.key?(name_str)
as_bool(@options[name_str])
else
default ? default.call : false
end
end
def string_option(name, &default)
as_string(@options.delete(name.to_s, &default))
end
def lexer_option(name, &default)
as_lexer(@options.delete(name.to_s, &default))
end
def list_option(name, &default)
as_list(@options.delete(name.to_s, &default))
end
def token_option(name, &default)
as_token(@options.delete(name.to_s, &default))
end
def hash_option(name, defaults, &val_cast)
name = name.to_s
out = defaults.dup
base = @options.delete(name.to_s)
base = {} unless base.is_a?(Hash)
base.each { |k, v| out[k.to_s] = val_cast ? val_cast.call(v) : v }
@options.keys.each do |key|
next unless key =~ /(\w+)\[(\w+)\]/ and $1 == name
value = @options.delete(key)
out[$2] = val_cast ? val_cast.call(value) : value
end
out
end
# @abstract
#
# Called after each lex is finished. The default implementation
# is a noop.
def reset!
end
# Given a string, yield [token, chunk] pairs. If no block is given,
# an enumerator is returned.
#
# @option opts :continue
# Continue the lex from the previous state (i.e. don't call #reset!)
#
# @note The use of :continue => true has been deprecated. A warning is
# issued if run with `$VERBOSE` set to true.
#
# @note The use of arbitrary `opts` has never been supported, but we
# previously ignored them with no error. We now warn unconditionally.
def lex(string, opts=nil, &b)
if opts
if (opts.keys - [:continue]).size > 0
# improper use of options hash
warn('Improper use of Lexer#lex - this method does not receive options.' +
' This will become an error in a future version.')
end
if opts[:continue]
warn '`lex :continue => true` is deprecated, please use #continue_lex instead'
return continue_lex(string, &b)
end
end
return enum_for(:lex, string) unless block_given?
Lexer.assert_utf8!(string)
reset!
continue_lex(string, &b)
end
# Continue the lex from the the current state without resetting
def continue_lex(string, &b)
return enum_for(:continue_lex, string, &b) unless block_given?
# consolidate consecutive tokens of the same type
last_token = nil
last_val = nil
stream_tokens(string) do |tok, val|
next if val.empty?
if tok == last_token
last_val << val
next
end
b.call(last_token, last_val) if last_token
last_token = tok
last_val = val
end
b.call(last_token, last_val) if last_token
end
# delegated to {Lexer.tag}
def tag
self.class.tag
end
# @abstract
#
# Yield `[token, chunk]` pairs, given a prepared input stream. This
# must be implemented.
#
# @param [StringScanner] stream
# the stream
def stream_tokens(stream, &b)
raise 'abstract'
end
# @abstract
#
# Return true if there is an in-text indication (such as a shebang
# or DOCTYPE declaration) that this lexer should be used.
#
# @param [TextAnalyzer] text
# the text to be analyzed, with a couple of handy methods on it,
# like {TextAnalyzer#shebang?} and {TextAnalyzer#doctype?}
def self.detect?(text)
false
end
end
module Lexers
BASE_DIR = "#{__dir__}/lexers".freeze
@_loaded_lexers = {}
def self.load_lexer(relpath)
return if @_loaded_lexers.key?(relpath)
@_loaded_lexers[relpath] = true
Kernel::load File.join(BASE_DIR, relpath)
end
end
end