class RuboCop::Cop::Style::EmptyLiteral

This cop checks for the use of a method, the result of which would be a literal, like an empty array, hash, or string.

@example

# bad
a = Array.new
h = Hash.new
s = String.new

# good
a = []
h = {}
s = ''

Constants

ARR_MSG
HASH_MSG
STR_MSG

Public Instance Methods

autocorrect(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 49
def autocorrect(node)
  lambda do |corrector|
    corrector.replace(replacement_range(node), correction(node))
  end
end
on_send(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 36
def on_send(node)
  add_offense(node, message: ARR_MSG)  if offense_array_node?(node)
  add_offense(node, message: HASH_MSG) if offense_hash_node?(node)

  str_node(node) do
    return if frozen_string_literals_enabled?

    add_offense(node,
                message: format(STR_MSG,
                                prefer: preferred_string_literal))
  end
end

Private Instance Methods

correction(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 103
def correction(node)
  if offense_array_node?(node)
    '[]'
  elsif str_node(node)
    preferred_string_literal
  elsif offense_hash_node?(node)
    if first_argument_unparenthesized?(node)
      # `some_method {}` is not same as `some_method Hash.new`
      # because the braces are interpreted as a block. We will have
      # to rewrite the arguments to wrap them in parenthesis.
      args = node.parent.arguments
      "(#{args[1..-1].map(&:source).unshift('{}').join(', ')})"
    else
      '{}'
    end
  end
end
enforce_double_quotes?() click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 61
def enforce_double_quotes?
  string_literals_config['EnforcedStyle'] == 'double_quotes'
end
first_argument_unparenthesized?(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 69
def first_argument_unparenthesized?(node)
  parent = node.parent
  unless parent && %i[send super zsuper].include?(parent.type)
    return false
  end

  node.object_id == parent.arguments.first.object_id &&
    !parentheses?(node.parent)
end
offense_array_node?(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 94
def offense_array_node?(node)
  array_node(node) && !array_with_block(node.parent)
end
offense_hash_node?(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 98
def offense_hash_node?(node)
  # If Hash.new takes a block, it can't be changed to {}.
  hash_node(node) && !hash_with_block(node.parent)
end
preferred_string_literal() click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 57
def preferred_string_literal
  enforce_double_quotes? ? '""' : "''"
end
replacement_range(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 79
def replacement_range(node)
  if hash_node(node) &&
     first_argument_unparenthesized?(node)
    # `some_method {}` is not same as `some_method Hash.new`
    # because the braces are interpreted as a block. We will have
    # to rewrite the arguments to wrap them in parenthesis.
    args = node.parent.arguments

    range_between(args[0].loc.expression.begin_pos - 1,
                  args[-1].loc.expression.end_pos)
  else
    node.source_range
  end
end
string_literals_config() click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 65
def string_literals_config
  config.for_cop('Style/StringLiterals')
end