Class: Parser::Source::Rewriter

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

Overview

Rewriter performs the heavy lifting in the source rewriting process. It schedules code updates to be performed in the correct order and verifies that no two updates clobber each other, that is, attempt to modify the same part of code.

If it is detected that one update clobbers another one, an :error and a :note diagnostics describing both updates are generated and passed to the diagnostic engine. After that, an exception is raised.

The default diagnostic engine consumer simply prints the diagnostics to stderr.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(source_buffer) ⇒ Rewriter

Returns a new instance of Rewriter.

Parameters:



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# File 'lib/parser/source/rewriter.rb', line 31

def initialize(source_buffer)
  @diagnostics = Diagnostic::Engine.new
  @diagnostics.consumer = lambda do |diag|
    $stderr.puts diag.render
  end

  @source_buffer = source_buffer
  @queue         = []
  @clobber       = 0
end

Instance Attribute Details

#diagnostics ⇒ Diagnostic::Engine (readonly)

Returns:



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# File 'lib/parser/source/rewriter.rb', line 24

class Rewriter
  attr_reader :source_buffer
  attr_reader :diagnostics

  ##
  # @param [Source::Buffer] source_buffer
  #
  def initialize(source_buffer)
    @diagnostics = Diagnostic::Engine.new
    @diagnostics.consumer = lambda do |diag|
      $stderr.puts diag.render
    end

    @source_buffer = source_buffer
    @queue         = []
    @clobber       = 0
  end

  ##
  # Removes the source range.
  #
  # @param [Range] range
  # @return [Rewriter] self
  # @raise [RuntimeError] when clobbering is detected
  #
  def remove(range)
    append Rewriter::Action.new(range, '')
  end

  ##
  # Inserts new code before the given source range.
  #
  # @param [Range] range
  # @param [String] content
  # @return [Rewriter] self
  # @raise [RuntimeError] when clobbering is detected
  #
  def insert_before(range, content)
    append Rewriter::Action.new(range.begin, content)
  end

  ##
  # Inserts new code after the given source range.
  #
  # @param [Range] range
  # @param [String] content
  # @return [Rewriter] self
  # @raise [RuntimeError] when clobbering is detected
  #
  def insert_after(range, content)
    append Rewriter::Action.new(range.end, content)
  end

  ##
  # Replaces the code of the source range `range` with `content`.
  #
  # @param [Range] range
  # @param [String] content
  # @return [Rewriter] self
  # @raise [RuntimeError] when clobbering is detected
  #
  def replace(range, content)
    append Rewriter::Action.new(range, content)
  end

  ##
  # Applies all scheduled changes to the `source_buffer` and returns
  # modified source as a new string.
  #
  # @return [String]
  #
  def process
    adjustment = 0
    source     = @source_buffer.source.dup

    sorted_queue = @queue.sort_by.with_index do |action, index|
      [action.range.begin_pos, index]
    end

    sorted_queue.each do |action|
      begin_pos = action.range.begin_pos + adjustment
      end_pos   = begin_pos + action.range.length

      source[begin_pos...end_pos] = action.replacement

      adjustment += (action.replacement.length - action.range.length)
    end

    source
  end

  private

  def append(action)
    if (clobber_action = clobbered?(action.range))
      # cannot replace 3 characters with "foobar"
      diagnostic = Diagnostic.new(:error,
                                  :invalid_action,
                                  { :action => action },
                                  action.range)
      @diagnostics.process(diagnostic)

      # clobbered by: remove 3 characters
      diagnostic = Diagnostic.new(:note,
                                  :clobbered,
                                  { :action => clobber_action },
                                  clobber_action.range)
      @diagnostics.process(diagnostic)

      raise RuntimeError, "Parser::Source::Rewriter detected clobbering"
    else
      clobber(action.range)

      @queue << action
    end

    self
  end

  def clobber(range)
    @clobber |= (2 ** range.size - 1) << range.begin_pos
  end

  def clobbered?(range)
    if @clobber & ((2 ** range.size - 1) << range.begin_pos) != 0
      @queue.find do |action|
        action.range.to_a & range.to_a
      end
    end
  end
end

#source_buffer ⇒ Source::Buffer (readonly)

Returns:



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# File 'lib/parser/source/rewriter.rb', line 24

class Rewriter
  attr_reader :source_buffer
  attr_reader :diagnostics

  ##
  # @param [Source::Buffer] source_buffer
  #
  def initialize(source_buffer)
    @diagnostics = Diagnostic::Engine.new
    @diagnostics.consumer = lambda do |diag|
      $stderr.puts diag.render
    end

    @source_buffer = source_buffer
    @queue         = []
    @clobber       = 0
  end

  ##
  # Removes the source range.
  #
  # @param [Range] range
  # @return [Rewriter] self
  # @raise [RuntimeError] when clobbering is detected
  #
  def remove(range)
    append Rewriter::Action.new(range, '')
  end

  ##
  # Inserts new code before the given source range.
  #
  # @param [Range] range
  # @param [String] content
  # @return [Rewriter] self
  # @raise [RuntimeError] when clobbering is detected
  #
  def insert_before(range, content)
    append Rewriter::Action.new(range.begin, content)
  end

  ##
  # Inserts new code after the given source range.
  #
  # @param [Range] range
  # @param [String] content
  # @return [Rewriter] self
  # @raise [RuntimeError] when clobbering is detected
  #
  def insert_after(range, content)
    append Rewriter::Action.new(range.end, content)
  end

  ##
  # Replaces the code of the source range `range` with `content`.
  #
  # @param [Range] range
  # @param [String] content
  # @return [Rewriter] self
  # @raise [RuntimeError] when clobbering is detected
  #
  def replace(range, content)
    append Rewriter::Action.new(range, content)
  end

  ##
  # Applies all scheduled changes to the `source_buffer` and returns
  # modified source as a new string.
  #
  # @return [String]
  #
  def process
    adjustment = 0
    source     = @source_buffer.source.dup

    sorted_queue = @queue.sort_by.with_index do |action, index|
      [action.range.begin_pos, index]
    end

    sorted_queue.each do |action|
      begin_pos = action.range.begin_pos + adjustment
      end_pos   = begin_pos + action.range.length

      source[begin_pos...end_pos] = action.replacement

      adjustment += (action.replacement.length - action.range.length)
    end

    source
  end

  private

  def append(action)
    if (clobber_action = clobbered?(action.range))
      # cannot replace 3 characters with "foobar"
      diagnostic = Diagnostic.new(:error,
                                  :invalid_action,
                                  { :action => action },
                                  action.range)
      @diagnostics.process(diagnostic)

      # clobbered by: remove 3 characters
      diagnostic = Diagnostic.new(:note,
                                  :clobbered,
                                  { :action => clobber_action },
                                  clobber_action.range)
      @diagnostics.process(diagnostic)

      raise RuntimeError, "Parser::Source::Rewriter detected clobbering"
    else
      clobber(action.range)

      @queue << action
    end

    self
  end

  def clobber(range)
    @clobber |= (2 ** range.size - 1) << range.begin_pos
  end

  def clobbered?(range)
    if @clobber & ((2 ** range.size - 1) << range.begin_pos) != 0
      @queue.find do |action|
        action.range.to_a & range.to_a
      end
    end
  end
end

Instance Method Details

#insert_after(range, content) ⇒ Rewriter

Inserts new code after the given source range.

Parameters:

Returns:

Raises:

  • (RuntimeError) —

    when clobbering is detected



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# File 'lib/parser/source/rewriter.rb', line 73

def insert_after(range, content)
  append Rewriter::Action.new(range.end, content)
end

#insert_before(range, content) ⇒ Rewriter

Inserts new code before the given source range.

Parameters:

Returns:

Raises:

  • (RuntimeError) —

    when clobbering is detected



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# File 'lib/parser/source/rewriter.rb', line 61

def insert_before(range, content)
  append Rewriter::Action.new(range.begin, content)
end

#process ⇒ String

Applies all scheduled changes to the source_buffer and returns modified source as a new string.

Returns:



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# File 'lib/parser/source/rewriter.rb', line 95

def process
  adjustment = 0
  source     = @source_buffer.source.dup

  sorted_queue = @queue.sort_by.with_index do |action, index|
    [action.range.begin_pos, index]
  end

  sorted_queue.each do |action|
    begin_pos = action.range.begin_pos + adjustment
    end_pos   = begin_pos + action.range.length

    source[begin_pos...end_pos] = action.replacement

    adjustment += (action.replacement.length - action.range.length)
  end

  source
end

#remove(range) ⇒ Rewriter

Removes the source range.

Parameters:

Returns:

Raises:

  • (RuntimeError) —

    when clobbering is detected



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# File 'lib/parser/source/rewriter.rb', line 49

def remove(range)
  append Rewriter::Action.new(range, '')
end

#replace(range, content) ⇒ Rewriter

Replaces the code of the source range range with content.

Parameters:

Returns:

Raises:

  • (RuntimeError) —

    when clobbering is detected



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# File 'lib/parser/source/rewriter.rb', line 85

def replace(range, content)
  append Rewriter::Action.new(range, content)
end