Class: Parser::Source::Buffer

Inherits:
Object
  • Object
show all
Defined in:
lib/parser/source/buffer.rb

Overview

A buffer with source code. Buffer contains the source code itself, associated location information (name and first line), and takes care of encoding.

A source buffer is immutable once populated.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, first_line = 1, source: nil) ⇒ Buffer

Returns a new instance of Buffer.


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# File 'lib/parser/source/buffer.rb', line 105

def initialize(name, first_line = 1, source: nil)
  @name        = name.to_s
  @source      = nil
  @first_line  = first_line

  @lines       = nil
  @line_begins = nil

  # UTF-32-reencoded source for O(1) slicing
  @slice_source = nil

  # Cache for fast lookup
  @line_index_for_position = {}

  self.source = source if source
end

Instance Attribute Details

#first_lineInteger (readonly)

First line of the buffer, 1 by default.

Returns:

  • (Integer)

    first line


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# File 'lib/parser/source/buffer.rb', line 25

class Buffer
  attr_reader :name, :first_line

  ##
  # @api private
  #
  ENCODING_RE =
    /[\s#](en)?coding\s*[:=]\s*
      (
        # Special-case: there's a UTF8-MAC encoding.
        (utf8-mac)
      |
        # Chew the suffix; it's there for emacs compat.
        ([A-Za-z0-9_-]+?)(-unix|-dos|-mac)
      |
        ([A-Za-z0-9_-]+)
      )
    /x

  ##
  # Try to recognize encoding of `string` as Ruby would, i.e. by looking for
  # magic encoding comment or UTF-8 BOM. `string` can be in any encoding.
  #
  # @param [String]  string
  # @return [String, nil] encoding name, if recognized
  #
  def self.recognize_encoding(string)
    return if string.empty?

    # extract the first two lines in an efficient way
    string =~ /\A(.*)\n?(.*\n)?/
    first_line, second_line = $1, $2

    if first_line.start_with?("\xef\xbb\xbf".freeze) # BOM
      return Encoding::UTF_8
    elsif first_line[0, 2] == '#!'.freeze
      encoding_line = second_line
    else
      encoding_line = first_line
    end

    return nil if encoding_line.nil? || encoding_line[0] != '#'

    if (result = ENCODING_RE.match(encoding_line))
      Encoding.find(result[3] || result[4] || result[6])
    else
      nil
    end
  end

  ##
  # Recognize encoding of `input` and process it so it could be lexed.
  #
  #  * If `input` does not contain BOM or magic encoding comment, it is
  #    kept in the original encoding.
  #  * If the detected encoding is binary, `input` is kept in binary.
  #  * Otherwise, `input` is re-encoded into UTF-8 and returned as a
  #    new string.
  #
  # This method mutates the encoding of `input`, but not its content.
  #
  # @param  [String] input
  # @return [String]
  # @raise  [EncodingError]
  #
  def self.reencode_string(input)
    original_encoding = input.encoding
    detected_encoding = recognize_encoding(input.force_encoding(Encoding::BINARY))

    if detected_encoding.nil?
      input.force_encoding(original_encoding)
    elsif detected_encoding == Encoding::BINARY
      input
    else
      input.
        force_encoding(detected_encoding).
        encode(Encoding::UTF_8)
    end
  end

  def initialize(name, first_line = 1, source: nil)
    @name        = name.to_s
    @source      = nil
    @first_line  = first_line

    @lines       = nil
    @line_begins = nil

    # UTF-32-reencoded source for O(1) slicing
    @slice_source = nil

    # Cache for fast lookup
    @line_index_for_position = {}

    self.source = source if source
  end

  ##
  # Populate this buffer from correspondingly named file.
  #
  # @example
  #  Parser::Source::Buffer.new('foo/bar.rb').read
  #
  # @return [Buffer] self
  # @raise  [ArgumentError] if already populated
  #
  def read
    File.open(@name, 'rb') do |io|
      self.source = io.read
    end

    self
  end

  ##
  # Source code contained in this buffer.
  #
  # @return [String] source code
  # @raise  [RuntimeError] if buffer is not populated yet
  #
  def source
    if @source.nil?
      raise RuntimeError, 'Cannot extract source from uninitialized Source::Buffer'
    end

    @source
  end

  ##
  # Populate this buffer from a string with encoding autodetection.
  # `input` is mutated if not frozen.
  #
  # @param [String] input
  # @raise [ArgumentError] if already populated
  # @raise [EncodingError] if `input` includes invalid byte sequence for the encoding
  # @return [String]
  #
  def source=(input)
    input = input.dup if input.frozen?
    input = self.class.reencode_string(input)

    unless input.valid_encoding?
      raise EncodingError, "invalid byte sequence in #{input.encoding.name}"
    end

    self.raw_source = input
  end

  ##
  # Populate this buffer from a string without encoding autodetection.
  #
  # @param [String] input
  # @raise [ArgumentError] if already populated
  # @return [String]
  #
  def raw_source=(input)
    if @source
      raise ArgumentError, 'Source::Buffer is immutable'
    end

    @source = input.gsub("\r\n".freeze, "\n".freeze).freeze

    if !@source.ascii_only? &&
       @source.encoding != Encoding::UTF_32LE &&
       @source.encoding != Encoding::BINARY
      @slice_source = @source.encode(Encoding::UTF_32LE)
    end
  end

  def slice(range)
    if @slice_source.nil?
      @source[range]
    else
      @slice_source[range].encode(@source.encoding)
    end
  end

  ##
  # Convert a character index into the source to a `[line, column]` tuple.
  #
  # @param  [Integer] position
  # @return [[Integer, Integer]] `[line, column]`
  #
  def decompose_position(position)
    line_index = line_index_for_position(position)
    line_begin = line_begins[line_index]

    [ @first_line + line_index , position - line_begin ]
  end

  ##
  # Convert a character index into the source to a line number.
  #
  # @param  [Integer] position
  # @return [Integer] line
  # @api private
  #
  def line_for_position(position)
    line_index_for_position(position) + @first_line
  end

  ##
  # Convert a character index into the source to a column number.
  #
  # @param  [Integer] position
  # @return [Integer] column
  # @api private
  #
  def column_for_position(position)
    line_index = line_index_for_position(position)
    position - line_begins[line_index]
  end

  ##
  # Return an `Array` of source code lines.
  #
  # @return [Array<String>]
  #
  def source_lines
    @lines ||= begin
      lines = @source.lines.to_a
      lines << ''.dup if @source.end_with?("\n".freeze)

      lines.each do |line|
        line.chomp!("\n".freeze)
        line.freeze
      end

      lines.freeze
    end
  end

  ##
  # Extract line `lineno` from source, taking `first_line` into account.
  #
  # @param  [Integer] lineno
  # @return [String]
  # @raise  [IndexError] if `lineno` is out of bounds
  #
  def source_line(lineno)
    source_lines.fetch(lineno - @first_line).dup
  end

  ##
  # Extract line `lineno` as a new `Range`, taking `first_line` into account.
  #
  # @param  [Integer] lineno
  # @return [Range]
  # @raise  [IndexError] if `lineno` is out of bounds
  #
  def line_range(lineno)
    index = lineno - @first_line
    if index < 0 || index + 1 >= line_begins.size
      raise IndexError, 'Parser::Source::Buffer: range for line ' \
        "#{lineno} requested, valid line numbers are #{@first_line}.." \
        "#{@first_line + line_begins.size - 2}"
    else
      Range.new(self, line_begins[index], line_begins[index + 1] - 1)
    end
  end

  ##
  # @return [Range] A range covering the whole source
  #
  def source_range
    @source_range ||= Range.new(self, 0, source.size)
  end

  ##
  # Number of last line in the buffer
  #
  # @return [Integer]
  #
  def last_line
    line_begins.size + @first_line - 2
  end

  # :nodoc:
  def freeze
    source_lines; line_begins; source_range # build cache
    super
  end

  # :nodoc:
  def inspect
    "#<#{self.class} #{name}>"
  end

  private

  # @returns [0, line_begin_of_line_1, ..., source.size + 1]
  def line_begins
    @line_begins ||= begin
      begins = [0]
      index = 0
      while index = @source.index("\n".freeze, index)
        index += 1
        begins << index
      end
      begins << @source.size + 1
      begins
    end
  end

  # @returns 0-based line index of position
  def line_index_for_position(position)
    @line_index_for_position[position] || begin
      index = bsearch(line_begins, position) - 1
      @line_index_for_position[position] = index unless @line_index_for_position.frozen?
      index
    end
  end

  if Array.method_defined?(:bsearch_index) # RUBY_VERSION >= 2.3
    def bsearch(line_begins, position)
      line_begins.bsearch_index do |line_begin|
        position < line_begin
      end || line_begins.size - 1 # || only for out of bound values
    end
  else
    def bsearch(line_begins, position)
      @line_range ||= 0...line_begins.size
      @line_range.bsearch do |i|
        position < line_begins[i]
      end || line_begins.size - 1 # || only for out of bound values
    end
  end
end

#nameString (readonly)

Buffer name. If the buffer was created from a file, the name corresponds to relative path to the file.

Returns:

  • (String)

    buffer name


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# File 'lib/parser/source/buffer.rb', line 25

class Buffer
  attr_reader :name, :first_line

  ##
  # @api private
  #
  ENCODING_RE =
    /[\s#](en)?coding\s*[:=]\s*
      (
        # Special-case: there's a UTF8-MAC encoding.
        (utf8-mac)
      |
        # Chew the suffix; it's there for emacs compat.
        ([A-Za-z0-9_-]+?)(-unix|-dos|-mac)
      |
        ([A-Za-z0-9_-]+)
      )
    /x

  ##
  # Try to recognize encoding of `string` as Ruby would, i.e. by looking for
  # magic encoding comment or UTF-8 BOM. `string` can be in any encoding.
  #
  # @param [String]  string
  # @return [String, nil] encoding name, if recognized
  #
  def self.recognize_encoding(string)
    return if string.empty?

    # extract the first two lines in an efficient way
    string =~ /\A(.*)\n?(.*\n)?/
    first_line, second_line = $1, $2

    if first_line.start_with?("\xef\xbb\xbf".freeze) # BOM
      return Encoding::UTF_8
    elsif first_line[0, 2] == '#!'.freeze
      encoding_line = second_line
    else
      encoding_line = first_line
    end

    return nil if encoding_line.nil? || encoding_line[0] != '#'

    if (result = ENCODING_RE.match(encoding_line))
      Encoding.find(result[3] || result[4] || result[6])
    else
      nil
    end
  end

  ##
  # Recognize encoding of `input` and process it so it could be lexed.
  #
  #  * If `input` does not contain BOM or magic encoding comment, it is
  #    kept in the original encoding.
  #  * If the detected encoding is binary, `input` is kept in binary.
  #  * Otherwise, `input` is re-encoded into UTF-8 and returned as a
  #    new string.
  #
  # This method mutates the encoding of `input`, but not its content.
  #
  # @param  [String] input
  # @return [String]
  # @raise  [EncodingError]
  #
  def self.reencode_string(input)
    original_encoding = input.encoding
    detected_encoding = recognize_encoding(input.force_encoding(Encoding::BINARY))

    if detected_encoding.nil?
      input.force_encoding(original_encoding)
    elsif detected_encoding == Encoding::BINARY
      input
    else
      input.
        force_encoding(detected_encoding).
        encode(Encoding::UTF_8)
    end
  end

  def initialize(name, first_line = 1, source: nil)
    @name        = name.to_s
    @source      = nil
    @first_line  = first_line

    @lines       = nil
    @line_begins = nil

    # UTF-32-reencoded source for O(1) slicing
    @slice_source = nil

    # Cache for fast lookup
    @line_index_for_position = {}

    self.source = source if source
  end

  ##
  # Populate this buffer from correspondingly named file.
  #
  # @example
  #  Parser::Source::Buffer.new('foo/bar.rb').read
  #
  # @return [Buffer] self
  # @raise  [ArgumentError] if already populated
  #
  def read
    File.open(@name, 'rb') do |io|
      self.source = io.read
    end

    self
  end

  ##
  # Source code contained in this buffer.
  #
  # @return [String] source code
  # @raise  [RuntimeError] if buffer is not populated yet
  #
  def source
    if @source.nil?
      raise RuntimeError, 'Cannot extract source from uninitialized Source::Buffer'
    end

    @source
  end

  ##
  # Populate this buffer from a string with encoding autodetection.
  # `input` is mutated if not frozen.
  #
  # @param [String] input
  # @raise [ArgumentError] if already populated
  # @raise [EncodingError] if `input` includes invalid byte sequence for the encoding
  # @return [String]
  #
  def source=(input)
    input = input.dup if input.frozen?
    input = self.class.reencode_string(input)

    unless input.valid_encoding?
      raise EncodingError, "invalid byte sequence in #{input.encoding.name}"
    end

    self.raw_source = input
  end

  ##
  # Populate this buffer from a string without encoding autodetection.
  #
  # @param [String] input
  # @raise [ArgumentError] if already populated
  # @return [String]
  #
  def raw_source=(input)
    if @source
      raise ArgumentError, 'Source::Buffer is immutable'
    end

    @source = input.gsub("\r\n".freeze, "\n".freeze).freeze

    if !@source.ascii_only? &&
       @source.encoding != Encoding::UTF_32LE &&
       @source.encoding != Encoding::BINARY
      @slice_source = @source.encode(Encoding::UTF_32LE)
    end
  end

  def slice(range)
    if @slice_source.nil?
      @source[range]
    else
      @slice_source[range].encode(@source.encoding)
    end
  end

  ##
  # Convert a character index into the source to a `[line, column]` tuple.
  #
  # @param  [Integer] position
  # @return [[Integer, Integer]] `[line, column]`
  #
  def decompose_position(position)
    line_index = line_index_for_position(position)
    line_begin = line_begins[line_index]

    [ @first_line + line_index , position - line_begin ]
  end

  ##
  # Convert a character index into the source to a line number.
  #
  # @param  [Integer] position
  # @return [Integer] line
  # @api private
  #
  def line_for_position(position)
    line_index_for_position(position) + @first_line
  end

  ##
  # Convert a character index into the source to a column number.
  #
  # @param  [Integer] position
  # @return [Integer] column
  # @api private
  #
  def column_for_position(position)
    line_index = line_index_for_position(position)
    position - line_begins[line_index]
  end

  ##
  # Return an `Array` of source code lines.
  #
  # @return [Array<String>]
  #
  def source_lines
    @lines ||= begin
      lines = @source.lines.to_a
      lines << ''.dup if @source.end_with?("\n".freeze)

      lines.each do |line|
        line.chomp!("\n".freeze)
        line.freeze
      end

      lines.freeze
    end
  end

  ##
  # Extract line `lineno` from source, taking `first_line` into account.
  #
  # @param  [Integer] lineno
  # @return [String]
  # @raise  [IndexError] if `lineno` is out of bounds
  #
  def source_line(lineno)
    source_lines.fetch(lineno - @first_line).dup
  end

  ##
  # Extract line `lineno` as a new `Range`, taking `first_line` into account.
  #
  # @param  [Integer] lineno
  # @return [Range]
  # @raise  [IndexError] if `lineno` is out of bounds
  #
  def line_range(lineno)
    index = lineno - @first_line
    if index < 0 || index + 1 >= line_begins.size
      raise IndexError, 'Parser::Source::Buffer: range for line ' \
        "#{lineno} requested, valid line numbers are #{@first_line}.." \
        "#{@first_line + line_begins.size - 2}"
    else
      Range.new(self, line_begins[index], line_begins[index + 1] - 1)
    end
  end

  ##
  # @return [Range] A range covering the whole source
  #
  def source_range
    @source_range ||= Range.new(self, 0, source.size)
  end

  ##
  # Number of last line in the buffer
  #
  # @return [Integer]
  #
  def last_line
    line_begins.size + @first_line - 2
  end

  # :nodoc:
  def freeze
    source_lines; line_begins; source_range # build cache
    super
  end

  # :nodoc:
  def inspect
    "#<#{self.class} #{name}>"
  end

  private

  # @returns [0, line_begin_of_line_1, ..., source.size + 1]
  def line_begins
    @line_begins ||= begin
      begins = [0]
      index = 0
      while index = @source.index("\n".freeze, index)
        index += 1
        begins << index
      end
      begins << @source.size + 1
      begins
    end
  end

  # @returns 0-based line index of position
  def line_index_for_position(position)
    @line_index_for_position[position] || begin
      index = bsearch(line_begins, position) - 1
      @line_index_for_position[position] = index unless @line_index_for_position.frozen?
      index
    end
  end

  if Array.method_defined?(:bsearch_index) # RUBY_VERSION >= 2.3
    def bsearch(line_begins, position)
      line_begins.bsearch_index do |line_begin|
        position < line_begin
      end || line_begins.size - 1 # || only for out of bound values
    end
  else
    def bsearch(line_begins, position)
      @line_range ||= 0...line_begins.size
      @line_range.bsearch do |i|
        position < line_begins[i]
      end || line_begins.size - 1 # || only for out of bound values
    end
  end
end

Class Method Details

.recognize_encoding(string) ⇒ String?

Try to recognize encoding of string as Ruby would, i.e. by looking for magic encoding comment or UTF-8 BOM. string can be in any encoding.

Parameters:

  • string (String)

Returns:

  • (String, nil)

    encoding name, if recognized


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# File 'lib/parser/source/buffer.rb', line 51

def self.recognize_encoding(string)
  return if string.empty?

  # extract the first two lines in an efficient way
  string =~ /\A(.*)\n?(.*\n)?/
  first_line, second_line = $1, $2

  if first_line.start_with?("\xef\xbb\xbf".freeze) # BOM
    return Encoding::UTF_8
  elsif first_line[0, 2] == '#!'.freeze
    encoding_line = second_line
  else
    encoding_line = first_line
  end

  return nil if encoding_line.nil? || encoding_line[0] != '#'

  if (result = ENCODING_RE.match(encoding_line))
    Encoding.find(result[3] || result[4] || result[6])
  else
    nil
  end
end

.reencode_string(input) ⇒ String

Recognize encoding of input and process it so it could be lexed.

  • If input does not contain BOM or magic encoding comment, it is kept in the original encoding.
  • If the detected encoding is binary, input is kept in binary.
  • Otherwise, input is re-encoded into UTF-8 and returned as a new string.

This method mutates the encoding of input, but not its content.

Parameters:

  • input (String)

Returns:

  • (String)

Raises:

  • (EncodingError)

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# File 'lib/parser/source/buffer.rb', line 90

def self.reencode_string(input)
  original_encoding = input.encoding
  detected_encoding = recognize_encoding(input.force_encoding(Encoding::BINARY))

  if detected_encoding.nil?
    input.force_encoding(original_encoding)
  elsif detected_encoding == Encoding::BINARY
    input
  else
    input.
      force_encoding(detected_encoding).
      encode(Encoding::UTF_8)
  end
end

Instance Method Details

#decompose_position(position) ⇒ [Integer, Integer]

Convert a character index into the source to a [line, column] tuple.

Parameters:

  • position (Integer)

Returns:

  • ([Integer, Integer])

    [line, column]


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# File 'lib/parser/source/buffer.rb', line 208

def decompose_position(position)
  line_index = line_index_for_position(position)
  line_begin = line_begins[line_index]

  [ @first_line + line_index , position - line_begin ]
end

#freezeObject

:nodoc:


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# File 'lib/parser/source/buffer.rb', line 303

def freeze
  source_lines; line_begins; source_range # build cache
  super
end

#inspectObject

:nodoc:


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# File 'lib/parser/source/buffer.rb', line 309

def inspect
  "#<#{self.class} #{name}>"
end

#last_lineInteger

Number of last line in the buffer

Returns:

  • (Integer)

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# File 'lib/parser/source/buffer.rb', line 298

def last_line
  line_begins.size + @first_line - 2
end

#line_range(lineno) ⇒ Range

Extract line lineno as a new Range, taking first_line into account.

Parameters:

  • lineno (Integer)

Returns:

Raises:

  • (IndexError)

    if lineno is out of bounds


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# File 'lib/parser/source/buffer.rb', line 275

def line_range(lineno)
  index = lineno - @first_line
  if index < 0 || index + 1 >= line_begins.size
    raise IndexError, 'Parser::Source::Buffer: range for line ' \
      "#{lineno} requested, valid line numbers are #{@first_line}.." \
      "#{@first_line + line_begins.size - 2}"
  else
    Range.new(self, line_begins[index], line_begins[index + 1] - 1)
  end
end

#raw_source=(input) ⇒ String

Populate this buffer from a string without encoding autodetection.

Parameters:

  • input (String)

Returns:

  • (String)

Raises:

  • (ArgumentError)

    if already populated


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# File 'lib/parser/source/buffer.rb', line 180

def raw_source=(input)
  if @source
    raise ArgumentError, 'Source::Buffer is immutable'
  end

  @source = input.gsub("\r\n".freeze, "\n".freeze).freeze

  if !@source.ascii_only? &&
     @source.encoding != Encoding::UTF_32LE &&
     @source.encoding != Encoding::BINARY
    @slice_source = @source.encode(Encoding::UTF_32LE)
  end
end

#readBuffer

Populate this buffer from correspondingly named file.

Examples:

Parser::Source::Buffer.new('foo/bar.rb').read

Returns:

Raises:

  • (ArgumentError)

    if already populated


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# File 'lib/parser/source/buffer.rb', line 131

def read
  File.open(@name, 'rb') do |io|
    self.source = io.read
  end

  self
end

#slice(range) ⇒ Object


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# File 'lib/parser/source/buffer.rb', line 194

def slice(range)
  if @slice_source.nil?
    @source[range]
  else
    @slice_source[range].encode(@source.encoding)
  end
end

#sourceString

Source code contained in this buffer.

Returns:

  • (String)

    source code

Raises:

  • (RuntimeError)

    if buffer is not populated yet


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# File 'lib/parser/source/buffer.rb', line 145

def source
  if @source.nil?
    raise RuntimeError, 'Cannot extract source from uninitialized Source::Buffer'
  end

  @source
end

#source=(input) ⇒ String

Populate this buffer from a string with encoding autodetection. input is mutated if not frozen.

Parameters:

  • input (String)

Returns:

  • (String)

Raises:

  • (ArgumentError)

    if already populated

  • (EncodingError)

    if input includes invalid byte sequence for the encoding


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# File 'lib/parser/source/buffer.rb', line 162

def source=(input)
  input = input.dup if input.frozen?
  input = self.class.reencode_string(input)

  unless input.valid_encoding?
    raise EncodingError, "invalid byte sequence in #{input.encoding.name}"
  end

  self.raw_source = input
end

#source_line(lineno) ⇒ String

Extract line lineno from source, taking first_line into account.

Parameters:

  • lineno (Integer)

Returns:

  • (String)

Raises:

  • (IndexError)

    if lineno is out of bounds


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# File 'lib/parser/source/buffer.rb', line 264

def source_line(lineno)
  source_lines.fetch(lineno - @first_line).dup
end

#source_linesArray<String>

Return an Array of source code lines.

Returns:

  • (Array<String>)

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# File 'lib/parser/source/buffer.rb', line 243

def source_lines
  @lines ||= begin
    lines = @source.lines.to_a
    lines << ''.dup if @source.end_with?("\n".freeze)

    lines.each do |line|
      line.chomp!("\n".freeze)
      line.freeze
    end

    lines.freeze
  end
end

#source_rangeRange

Returns A range covering the whole source.

Returns:

  • (Range)

    A range covering the whole source


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# File 'lib/parser/source/buffer.rb', line 289

def source_range
  @source_range ||= Range.new(self, 0, source.size)
end