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Class: RuboCop::Cop::Performance::IoReadlines

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, AutoCorrector, Base
Instance Chain:
self, RangeHelp, Base
Inherits: Base
  • Object
Defined in: lib/rubocop/cop/performance/io_readlines.rb

Overview

Identifies places where inefficient readlines method can be replaced by each_line to avoid fully loading file content into memory.

Examples:

# bad
File.readlines('testfile').each { |l| puts l }
IO.readlines('testfile', chomp: true).each { |l| puts l }

conn.readlines(10).map { |l| l.size }
file.readlines.find { |l| l.start_with?('#') }
file.readlines.each { |l| puts l }

# good
File.open('testfile', 'r').each_line { |l| puts l }
IO.open('testfile').each_line(chomp: true) { |l| puts l }

conn.each_line(10).map { |l| l.size }
file.each_line.find { |l| l.start_with?('#') }
file.each_line { |l| puts l }

Constant Summary

Instance Method Summary

Instance Method Details

#autocorrect(corrector, enumerable_call, readlines_call, receiver) (private)

[ GitHub ] 

  


# File 'lib/rubocop/cop/performance/io_readlines.rb', line 58



def autocorrect(corrector, enumerable_call, readlines_call, receiver)
  # We cannot safely correct `.readlines` method called on IO/File classes
  # due to its signature and we are not sure with implicit receiver
  # if it is called in the context of some instance or mentioned class.
  return if receiver.nil?

  range = correction_range(enumerable_call, readlines_call)

  if readlines_call.arguments?
    call_args = build_call_args(readlines_call.arguments)
    replacement = "each_line(#{call_args})"
  else
    replacement = 'each_line'
  end

  corrector.replace(range, replacement)
end


  








  

    #build_bad_method(enumerable_call)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/performance/io_readlines.rb', line 90



def build_bad_method(enumerable_call)
  "readlines.#{enumerable_call.method_name}"
end


  








  

    #build_call_args(call_args_node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/performance/io_readlines.rb', line 106



def build_call_args(call_args_node)
  call_args_node.map(&:source).join(', ')
end


  








  

    #build_good_method(enumerable_call)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/performance/io_readlines.rb', line 82



def build_good_method(enumerable_call)
  if enumerable_call.method?(:each)
    'each_line'
  else
    "each_line.#{enumerable_call.method_name}"
  end
end


  








  

    #correction_range(enumerable_call, readlines_call)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/performance/io_readlines.rb', line 94



def correction_range(enumerable_call, readlines_call)
  begin_pos = readlines_call.loc.selector.begin_pos

  end_pos = if enumerable_call.method?(:each)
              enumerable_call.source_range.end_pos
            else
              enumerable_call.loc.dot.begin_pos
            end

  range_between(begin_pos, end_pos)
end


  








  

    #offense_range(enumerable_call, readlines_call)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/performance/io_readlines.rb', line 76



def offense_range(enumerable_call, readlines_call)
  readlines_pos = readlines_call.loc.selector.begin_pos
  enumerable_pos = enumerable_call.loc.selector.end_pos
  range_between(readlines_pos, enumerable_pos)
end


  








  

    #on_send(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/performance/io_readlines.rb', line 42



def on_send(node)
  return unless (captured_values = readlines_on_class?(node) || readlines_on_instance?(node))

  enumerable_call, readlines_call, receiver = *captured_values

  range = offense_range(enumerable_call, readlines_call)
  good_method = build_good_method(enumerable_call)
  bad_method = build_bad_method(enumerable_call)

  add_offense(range, message: format(MSG, good: good_method, bad: bad_method)) do |corrector|
    autocorrect(corrector, enumerable_call, readlines_call, receiver)
  end
end