class RuboCop::Cop::Lint::Void

Checks for operators, variables, literals, lambda, proc and nonmutating methods used in void context.

‘each` blocks are allowed to prevent false positives. For example, the expression inside the `each` block below. It’s not void, especially when the receiver is an ‘Enumerator`:

source,ruby

enumerator = [1, 2, 3].filter enumerator.each { |item| item >= 2 } #=> [2, 3]


@example CheckForMethodsWithNoSideEffects: false (default)

# bad
def some_method
  some_num * 10
  do_something
end

def some_method(some_var)
  some_var
  do_something
end

@example CheckForMethodsWithNoSideEffects: true

# bad
def some_method(some_array)
  some_array.sort
  do_something(some_array)
end

# good
def some_method
  do_something
  some_num * 10
end

def some_method(some_var)
  do_something
  some_var
end

def some_method(some_array)
  some_array.sort!
  do_something(some_array)
end

Constants

BINARY_OPERATORS
CONST_MSG
EXPRESSION_MSG
LIT_MSG
METHODS_REPLACEABLE_BY_EACH
NONMUTATING_METHODS
NONMUTATING_METHODS_WITH_BANG_VERSION
NONMUTATING_MSG
OPERATORS
OP_MSG
SELF_MSG
UNARY_OPERATORS
VAR_MSG

Public Instance Methods

on_begin(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 90
def on_begin(node)
  check_begin(node)
end
Also aliased as: on_kwbegin
on_block(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 81
def on_block(node)
  return unless node.body && !node.body.begin_type?
  return unless in_void_context?(node.body)

  check_void_op(node.body) { node.method?(:each) }
  check_expression(node.body)
end
Also aliased as: on_numblock
on_ensure(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 95
def on_ensure(node)
  check_ensure(node)
end
on_kwbegin(node)
Alias for: on_begin
on_numblock(node)
Alias for: on_block

Private Instance Methods

all_keys_entirely_literal?(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 258
def all_keys_entirely_literal?(node)
  node.each_key.all? { |key| entirely_literal?(key) }
end
all_values_entirely_literal?(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 262
def all_values_entirely_literal?(node)
  node.each_value.all? { |value| entirely_literal?(value) }
end
autocorrect_nonmutating_send(corrector, node, suggestion) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 236
def autocorrect_nonmutating_send(corrector, node, suggestion)
  send_node = if node.send_type?
                node
              else
                node.send_node
              end
  corrector.replace(send_node.loc.selector, suggestion)
end
autocorrect_void_expression(corrector, node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 230
def autocorrect_void_expression(corrector, node)
  return if node.parent.if_type? && node.parent.modifier_form?

  corrector.remove(range_with_surrounding_space(range: node.source_range, side: :left))
end
autocorrect_void_op(corrector, node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 218
def autocorrect_void_op(corrector, node)
  if node.arguments.empty?
    corrector.replace(node, node.receiver.source)
  else
    corrector.replace(
      range_with_surrounding_space(range: node.loc.selector, side: :both,
                                   newlines: false),
      "\n"
    )
  end
end
check_begin(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 101
def check_begin(node)
  expressions = *node
  expressions.pop unless in_void_context?(node)
  expressions.each do |expr|
    check_void_op(expr) do
      block_node = node.each_ancestor(:block).first

      block_node&.method?(:each)
    end

    check_expression(expr)
  end
end
check_ensure(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 198
def check_ensure(node)
  return unless (body = node.body)
  # NOTE: the `begin` node case is already handled via `on_begin`
  return if body.begin_type?

  check_void_op(body) do
    block_node = node.each_ancestor(:block).first
    block_node&.method?(:each)
  end

  check_expression(body)
end
check_expression(expr) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 115
def check_expression(expr)
  expr = expr.body if expr.if_type? && expr.modifier_form?

  check_literal(expr)
  check_var(expr)
  check_self(expr)
  check_void_expression(expr)
  return unless cop_config['CheckForMethodsWithNoSideEffects']

  check_nonmutating(expr)
end
check_literal(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 156
def check_literal(node)
  return if !entirely_literal?(node) || node.xstr_type? || node.range_type?

  add_offense(node, message: format(LIT_MSG, lit: node.source)) do |corrector|
    autocorrect_void_expression(corrector, node)
  end
end
check_nonmutating(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 180
def check_nonmutating(node)
  return if !node.send_type? && !node.block_type? && !node.numblock_type?

  method_name = node.method_name
  return unless NONMUTATING_METHODS.include?(method_name)

  suggestion = if METHODS_REPLACEABLE_BY_EACH.include?(method_name)
                 'each'
               else
                 "#{method_name}!"
               end
  add_offense(node,
              message: format(NONMUTATING_MSG, method: method_name,
                                               suggest: suggestion)) do |corrector|
    autocorrect_nonmutating_send(corrector, node, suggestion)
  end
end
check_self(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 164
def check_self(node)
  return unless node.self_type?

  add_offense(node, message: SELF_MSG) do |corrector|
    autocorrect_void_expression(corrector, node)
  end
end
check_var(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 138
def check_var(node)
  return unless node.variable? || node.const_type?

  if node.const_type?
    template = node.special_keyword? ? VAR_MSG : CONST_MSG

    offense_range = node
    message = format(template, var: node.source)
  else
    offense_range = node.loc.name
    message = format(VAR_MSG, var: node.loc.name.source)
  end

  add_offense(offense_range, message: message) do |corrector|
    autocorrect_void_expression(corrector, node)
  end
end
check_void_expression(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 172
def check_void_expression(node)
  return unless node.defined_type? || node.lambda_or_proc?

  add_offense(node, message: format(EXPRESSION_MSG, expression: node.source)) do |corrector|
    autocorrect_void_expression(corrector, node)
  end
end
check_void_op(node) { |node| ... } click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 127
def check_void_op(node, &block)
  node = node.children.first while node.begin_type?
  return unless node.send_type? && OPERATORS.include?(node.method_name)
  return if block && yield(node)

  add_offense(node.loc.selector,
              message: format(OP_MSG, op: node.method_name)) do |corrector|
    autocorrect_void_op(corrector, node)
  end
end
entirely_literal?(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 245
def entirely_literal?(node)
  case node.type
  when :array
    all_values_entirely_literal?(node)
  when :hash
    all_keys_entirely_literal?(node) && all_values_entirely_literal?(node)
  when :send, :csend
    node.method?(:freeze) && node.receiver && entirely_literal?(node.receiver)
  else
    node.literal?
  end
end
in_void_context?(node) click to toggle source
# File lib/rubocop/cop/lint/void.rb, line 211
def in_void_context?(node)
  parent = node.parent
  return false unless parent && parent.children.last == node

  parent.respond_to?(:void_context?) && parent.void_context?
end