class RuboCop::Cop::Style::EmptyLiteral

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
a = Array[]
h = Hash.new
h = Hash[]
s = String.new

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

Constants

ARR_MSG
HASH_MSG
RESTRICT_ON_SEND
STR_MSG

Public Instance Methods

on_send(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 69
def on_send(node)
  return unless (message = offense_message(node))

  add_offense(node, message: message) do |corrector|
    corrector.replace(replacement_range(node), correction(node))
  end
end

Private Instance Methods

correction(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 118
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..].map(&:source).unshift('{}').join(', ')})"
    else
      '{}'
    end
  end
end
first_argument_unparenthesized?(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 89
def first_argument_unparenthesized?(node)
  parent = node.parent
  return false unless parent && %i[send super zsuper].include?(parent.type)

  node.equal?(parent.first_argument) && !parentheses?(node.parent)
end
frozen_strings?() click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 136
def frozen_strings?
  return true if frozen_string_literals_enabled?

  frozen_string_cop_enabled = config.for_cop('Style/FrozenStringLiteralComment')['Enabled']
  frozen_string_cop_enabled &&
    !frozen_string_literals_disabled? &&
    string_literals_frozen_by_default?.nil?
end
offense_array_node?(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 109
def offense_array_node?(node)
  (array_node(node) && !array_with_block(node.parent)) || array_with_index(node)
end
offense_hash_node?(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 113
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)) || hash_with_index(node)
end
offense_message(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 79
def offense_message(node)
  if offense_array_node?(node)
    format(ARR_MSG, current: node.source)
  elsif offense_hash_node?(node)
    format(HASH_MSG, current: node.source)
  elsif str_node(node) && !frozen_strings?
    format(STR_MSG, prefer: preferred_string_literal)
  end
end
replacement_range(node) click to toggle source
# File lib/rubocop/cop/style/empty_literal.rb, line 96
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].source_range.begin_pos - 1, args[-1].source_range.end_pos)
  else
    node.source_range
  end
end