Class: RuboCop::Cop::Lecture::PreferMap

Inherits:
Base
  • Object
show all
Defined in:
lib/rubocop/cop/lecture/prefer_map.rb

Overview

‘each`メソッドは`map`メソッドで置き換えられることがあります。 eachメソッドの結果、Arrayを得ているときはmapで書き換え可能かを検討してみてください。

Examples:

# bad
result = []
[1,2,3].each do |x|
  result << x * 2
end

# good
[1,2,3].map do |x|
  x * 2
end

Constant Summary collapse

MSG = 
<<~STRING
  この`each`メソッドは`map`メソッドで置き換えられるかもしれません。
STRING

Instance Method Summary collapse

Instance Method Details

#on_block(node) ⇒ Object

TODO: auto correct



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# File 'lib/rubocop/cop/lecture/prefer_map.rb', line 29

def on_block(node)
  return unless node.child_nodes.any?{|x| x.respond_to?(:method_name) && x.method_name == :each}

  # mapに書き換え可能そうか
  begin
    map_potential_methods = [:<<, :push, :unshift]
    node.
      child_nodes.
      select{|x| x.respond_to?(:method_name)}.
      select{|x| map_potential_methods.include?(x.method_name) }.each do |map_potential_method_node|

      ## map_potential_methodsのレシーバの型がArrayであるかどうかをTypeProfで調査
      receiver_variable_name = node.child_nodes.last.receiver.node_parts.first.to_s
      rb_text = node.parent.source
      rb_text += "\np #{receiver_variable_name}" # TypeProf調査行
      target_line_number = rb_text.lines.count
      rb_files = [["target.rb", rb_text]]
      rbs_files = []

      output = StringIO.new(String.new("")) # make mutable String object
      options = { show_errors: true }
      config = TypeProf::ConfigData.new(rb_files: rb_files, rbs_files: rbs_files, output: output, max_sec: 5, options: options)
      TypeProf.analyze(config)
      #=> "# TypeProf 0.21.4\n\n# Revealed types\n#  target.rb:6 #=> Array[Integer]\n\n# Classes\n"
      expected_type = output.string.match(/target.rb:#{target_line_number}\s*#=>\s*(.+)$/).captures.first
      #=> Array[SomeClass] or untyped or somethings
      if expected_type.match(/(.+)\[.+\]/).captures.first == "Array"
        add_offense(node)
        return
      end
    end
  rescue => e
    # 解析失敗
    # p e
  end
end