class RuboCop::Node

`RuboCop::Node` is a subclass of `Parser::AST::Node`. It provides access to parent nodes and an object-oriented way to traverse an AST with the power of `Enumerable`.

It has predicate methods for every node type, like this:

@example

node.send_type?    # Equivalent to: `node.type == :send`
node.op_asgn_type? # Equivalent to: `node.type == :op_asgn`

# Non-word characters (other than a-zA-Z0-9_) in type names are omitted.
node.defined_type? # Equivalent to: `node.type == :defined?`

# Find the first lvar node under the receiver node.
lvar_node = node.each_descendant.find(&:lvar_type?)

Constants

BASIC_LITERALS
COMPARISON_OPERATORS
COMPOSITE_LITERALS
FALSEY_LITERALS
IMMUTABLE_LITERALS
KEYWORDS
LITERALS
MUTABLE_LITERALS
OPERATOR_KEYWORDS
REFERENCES
SPECIAL_KEYWORDS
TRUTHY_LITERALS
VARIABLES

Public Class Methods

def_matcher(method_name, pattern_str) click to toggle source
# File lib/rubocop/ast_node.rb, line 47
def def_matcher(method_name, pattern_str)
  compiler = RuboCop::NodePattern::Compiler.new(pattern_str, 'self')
  src = "def #{method_name}("                "#{compiler.emit_param_list});"                "#{compiler.emit_method_code};end"

  file, lineno = *caller.first.split(':')
  class_eval(src, file, lineno.to_i)
end
new(type, children = [], properties = {}) click to toggle source

@see rubydoc.info/gems/ast/AST/Node:initialize

Calls superclass method
# File lib/rubocop/ast_node.rb, line 59
def initialize(type, children = [], properties = {})
  @mutable_attributes = {}

  # ::AST::Node#initialize freezes itself.
  super

  # #parent= may be invoked multiple times for a node because there are
  # pending nodes while constructing AST and they are replaced later.
  # For example, `lvar` and `send` type nodes are initially created as an
  # `ident` type node and fixed to the appropriate type later.
  # So, the #parent attribute needs to be mutable.
  each_child_node do |child_node|
    child_node.parent = self unless child_node.complete?
  end
end

Public Instance Methods

ancestors() click to toggle source

Returns an array of ancestor nodes. This is a shorthand for `node.each_ancestor.to_a`.

@return [Array<Node>] an array of ancestor nodes

# File lib/rubocop/ast_node.rb, line 156
def ancestors
  each_ancestor.to_a
end
asgn_method_call?() click to toggle source
# File lib/rubocop/ast_node.rb, line 383
def asgn_method_call?
  !COMPARISON_OPERATORS.include?(method_name) &&
    method_name.to_s.end_with?('='.freeze)
end
basic_literal?() click to toggle source
# File lib/rubocop/ast_node.rb, line 396
def basic_literal?
  BASIC_LITERALS.include?(type)
end
binary_operation?() click to toggle source
# File lib/rubocop/ast_node.rb, line 464
def binary_operation?
  return false unless loc.respond_to?(:selector) && loc.selector
  Cop::Util.operator?(method_name) &&
    source_range.begin_pos != loc.selector.begin_pos
end
chained?() click to toggle source
# File lib/rubocop/ast_node.rb, line 470
def chained?
  return false if parent.nil? || !parent.send_type?
  receiver, _method_name, *_args = *parent
  equal?(receiver)
end
child_nodes() click to toggle source

Returns an array of child nodes. This is a shorthand for `node.each_child_node.to_a`.

@return [Array<Node>] an array of child nodes

# File lib/rubocop/ast_node.rb, line 196
def child_nodes
  each_child_node.to_a
end
complete!() click to toggle source
# File lib/rubocop/ast_node.rb, line 93
def complete!
  @mutable_attributes.freeze
  each_child_node(&:complete!)
end
complete?() click to toggle source
# File lib/rubocop/ast_node.rb, line 98
def complete?
  @mutable_attributes.frozen?
end
const_name() click to toggle source
# File lib/rubocop/ast_node.rb, line 291
def const_name
  return unless const_type?
  namespace, name = *self
  if namespace && !namespace.cbase_type?
    "#{namespace.const_name}::#{name}"
  else
    name.to_s
  end
end
defined_module() click to toggle source
# File lib/rubocop/ast_node.rb, line 309
def defined_module
  namespace, name = *defined_module0
  s(:const, namespace, name) if name
end
defined_module_name() click to toggle source
# File lib/rubocop/ast_node.rb, line 314
def defined_module_name
  (const = defined_module) && const.const_name
end
descendants() click to toggle source

Returns an array of descendant nodes. This is a shorthand for `node.each_descendant.to_a`.

@return [Array<Node>] an array of descendant nodes

# File lib/rubocop/ast_node.rb, line 234
def descendants
  each_descendant.to_a
end
each_ancestor(*types, &block) click to toggle source

Calls the given block for each ancestor node from parent to root. If no block is given, an `Enumerator` is returned.

@overload #each_ancestor

Yield all nodes.

@overload #each_ancestor(type)

Yield only nodes matching the type.
@param [Symbol] type a node type

@overload #each_ancestor(type_a, type_b, …)

Yield only nodes matching any of the types.
@param [Symbol] type_a a node type
@param [Symbol] type_b a node type

@overload #each_ancestor(types)

Yield only nodes matching any of types in the array.
@param [Array<Symbol>] types an array containing node types

@yieldparam [Node] node each ancestor node @return [self] if a block is given @return [Enumerator] if no block is given

# File lib/rubocop/ast_node.rb, line 140
def each_ancestor(*types, &block)
  return to_enum(__method__, *types) unless block_given?

  if types.empty?
    visit_ancestors(&block)
  else
    visit_ancestors_with_types(types, &block)
  end

  self
end
each_child_node(*types) { |child| ... } click to toggle source

Calls the given block for each child node. If no block is given, an `Enumerator` is returned.

Note that this is different from `node.children.each { |child| … }` which yields all children including non-node elements.

@overload #each_child_node

Yield all nodes.

@overload #each_child_node(type)

Yield only nodes matching the type.
@param [Symbol] type a node type

@overload #each_child_node(type_a, type_b, …)

Yield only nodes matching any of the types.
@param [Symbol] type_a a node type
@param [Symbol] type_b a node type

@overload #each_child_node(types)

Yield only nodes matching any of types in the array.
@param [Array<Symbol>] types an array containing node types

@yieldparam [Node] node each child node @return [self] if a block is given @return [Enumerator] if no block is given

# File lib/rubocop/ast_node.rb, line 181
def each_child_node(*types)
  return to_enum(__method__, *types) unless block_given?

  children.each do |child|
    next unless child.is_a?(Node)
    yield child if types.empty? || types.include?(child.type)
  end

  self
end
each_descendant(*types, &block) click to toggle source

Calls the given block for each descendant node with depth first order. If no block is given, an `Enumerator` is returned.

@overload #each_descendant

Yield all nodes.

@overload #each_descendant(type)

Yield only nodes matching the type.
@param [Symbol] type a node type

@overload #each_descendant(type_a, type_b, …)

Yield only nodes matching any of the types.
@param [Symbol] type_a a node type
@param [Symbol] type_b a node type

@overload #each_descendant(types)

Yield only nodes matching any of types in the array.
@param [Array<Symbol>] types an array containing node types

@yieldparam [Node] node each descendant node @return [self] if a block is given @return [Enumerator] if no block is given

# File lib/rubocop/ast_node.rb, line 218
def each_descendant(*types, &block)
  return to_enum(__method__, *types) unless block_given?

  if types.empty?
    visit_descendants(&block)
  else
    visit_descendants_with_types(types, &block)
  end

  self
end
each_node(*types) { |self| ... } click to toggle source

Calls the given block for the receiver and each descendant node in depth-first order. If no block is given, an `Enumerator` is returned.

This method would be useful when you treat the receiver node as the root of a tree and want to iterate over all nodes in the tree.

@overload #each_node

Yield all nodes.

@overload #each_node(type)

Yield only nodes matching the type.
@param [Symbol] type a node type

@overload #each_node(type_a, type_b, …)

Yield only nodes matching any of the types.
@param [Symbol] type_a a node type
@param [Symbol] type_b a node type

@overload #each_node(types)

Yield only nodes matching any of types in the array.
@param [Array<Symbol>] types an array containing node types

@yieldparam [Node] node each node @return [self] if a block is given @return [Enumerator] if no block is given

# File lib/rubocop/ast_node.rb, line 260
def each_node(*types, &block)
  return to_enum(__method__, *types) unless block_given?

  yield self if types.empty? || types.include?(type)

  if types.empty?
    visit_descendants(&block)
  else
    visit_descendants_with_types(types, &block)
  end

  self
end
falsey_literal?() click to toggle source
# File lib/rubocop/ast_node.rb, line 404
def falsey_literal?
  FALSEY_LITERALS.include?(type)
end
immutable_literal?() click to toggle source
# File lib/rubocop/ast_node.rb, line 412
def immutable_literal?
  IMMUTABLE_LITERALS.include?(type)
end
keyword?() click to toggle source
# File lib/rubocop/ast_node.rb, line 442
def keyword?
  return true if special_keyword? || keyword_not?
  return false unless KEYWORDS.include?(type)

  !OPERATOR_KEYWORDS.include?(type) || loc.operator.is?(type.to_s)
end
keyword_not?() click to toggle source
# File lib/rubocop/ast_node.rb, line 453
def keyword_not?
  _receiver, method_name, *args = *self
  args.empty? && method_name == :! && loc.selector.is?('not'.freeze)
end
literal?() click to toggle source
# File lib/rubocop/ast_node.rb, line 392
def literal?
  LITERALS.include?(type)
end
multiline?() click to toggle source

Predicates

# File lib/rubocop/ast_node.rb, line 374
def multiline?
  expr = loc.expression
  expr && (expr.first_line != expr.last_line)
end
mutable_literal?() click to toggle source
# File lib/rubocop/ast_node.rb, line 408
def mutable_literal?
  MUTABLE_LITERALS.include?(type)
end
new_class_or_module_block?(block_node) click to toggle source
# File lib/rubocop/ast_node.rb, line 362
def new_class_or_module_block?(block_node)
  receiver = block_node.receiver

  block_node.method_name == :new &&
    receiver && receiver.const_type? &&
    (receiver.const_name == 'Class' || receiver.const_name == 'Module') &&
    block_node.parent &&
    block_node.parent.casgn_type?
end
parent() click to toggle source

Returns the parent node, or `nil` if the receiver is a root node.

@return [Node, nil] the parent node or `nil`

# File lib/rubocop/ast_node.rb, line 85
def parent
  @mutable_attributes[:parent]
end
parent_module_name() click to toggle source

Searching the AST

# File lib/rubocop/ast_node.rb, line 320
def parent_module_name
  # what class or module is this method/constant/etc definition in?
  # returns nil if answer cannot be determined
  ancestors = each_ancestor(:class, :module, :sclass, :casgn, :block)
  result    = ancestors.map do |ancestor|
    case ancestor.type
    when :class, :module, :casgn
      # TODO: if constant name has cbase (leading ::), then we don't need
      # to keep traversing up through nested classes/modules
      ancestor.defined_module_name
    when :sclass
      return parent_module_name_for_sclass(ancestor)
    else # block
      if ancestor.method_name == :class_eval
        # `class_eval` with no receiver applies to whatever module or class
        # we are currently in
        next unless (receiver = ancestor.receiver)
        return nil unless receiver.const_type?
        receiver.const_name
      elsif new_class_or_module_block?(ancestor)
        # we will catch this in the `casgn` branch above
        next
      else
        return nil
      end
    end
  end.compact.reverse.join('::')
  result.empty? ? 'Object' : result
end
parent_module_name_for_sclass(sclass_node) click to toggle source
# File lib/rubocop/ast_node.rb, line 350
def parent_module_name_for_sclass(sclass_node)
  # TODO: look for constant definition and see if it is nested
  # inside a class or module
  subject = sclass_node.children[0]

  if subject.const_type?
    "#<Class:#{subject.const_name}>"
  elsif subject.self_type?
    "#<Class:#{sclass_node.parent_module_name}>"
  end
end
pure?() click to toggle source

Some expressions are evaluated for their value, some for their side effects, and some for both If we know that expressions are useful only for their return values, and have no side effects, that means we can reorder them, change the number of times they are evaluated, or replace them with other expressions which are equivalent in value So, is evaluation of this node free of side effects?

# File lib/rubocop/ast_node.rb, line 539
def pure?
  # Be conservative and return false if we're not sure
  case type
  when :__FILE__, :__LINE__, :const, :cvar, :defined?, :false, :float,
       :gvar, :int, :ivar, :lvar, :nil, :str, :sym, :true, :regopt
    true
  when :and, :array, :begin, :case, :dstr, :dsym, :eflipflop, :ensure,
       :erange, :for, :hash, :if, :iflipflop, :irange, :kwbegin, :not, :or,
       :pair, :regexp, :until, :until_post, :when, :while, :while_post
    child_nodes.all?(&:pure?)
  else
    false
  end
end
reference?() click to toggle source
# File lib/rubocop/ast_node.rb, line 438
def reference?
  REFERENCES.include?(type)
end
sibling_index() click to toggle source

Returns the index of the receiver node in its siblings.

@return [Integer] the index of the receiver node in its siblings

# File lib/rubocop/ast_node.rb, line 118
def sibling_index
  parent.children.index { |sibling| sibling.equal?(self) }
end
single_line?() click to toggle source
# File lib/rubocop/ast_node.rb, line 379
def single_line?
  !multiline?
end
source() click to toggle source
# File lib/rubocop/ast_node.rb, line 274
def source
  loc.expression.source
end
source_range() click to toggle source
# File lib/rubocop/ast_node.rb, line 278
def source_range
  loc.expression
end
special_keyword?() click to toggle source
# File lib/rubocop/ast_node.rb, line 449
def special_keyword?
  SPECIAL_KEYWORDS.include?(source)
end
truthy_literal?() click to toggle source
# File lib/rubocop/ast_node.rb, line 400
def truthy_literal?
  TRUTHY_LITERALS.include?(type)
end
unary_operation?() click to toggle source
# File lib/rubocop/ast_node.rb, line 458
def unary_operation?
  return false unless loc.respond_to?(:selector) && loc.selector
  Cop::Util.operator?(loc.selector.source.to_sym) &&
    source_range.begin_pos == loc.selector.begin_pos
end
updated(type = nil, children = nil, properties = {}) click to toggle source

Override `AST::Node#updated` so that `AST::Processor` does not try to mutate our ASTs. Since we keep references from children to parents and not just the other way around, we cannot update an AST and share identical subtrees. Rather, the entire AST must be copied any time any part of it is changed.

# File lib/rubocop/ast_node.rb, line 110
def updated(type = nil, children = nil, properties = {})
  properties[:location] ||= @location
  Node.new(type || @type, children || @children, properties)
end
value_used?() click to toggle source

Some expressions are evaluated for their value, some for their side effects, and some for both If we know that an expression is useful only for its side effects, that means we can transform it in ways which preserve the side effects, but change the return value So, does the return value of this node matter? If we changed it to `(…; nil)`, might that affect anything?

# File lib/rubocop/ast_node.rb, line 502
def value_used?
  # Be conservative and return true if we're not sure
  return false if parent.nil?
  index = parent.children.index { |child| child.equal?(self) }

  case parent.type
  when :array, :defined?, :dstr, :dsym, :eflipflop, :erange, :float,
       :hash, :iflipflop, :irange, :not, :pair, :regexp, :str, :sym, :when,
       :xstr
    parent.value_used?
  when :begin, :kwbegin
    # the last child node determines the value of the parent
    index == parent.children.size - 1 ? parent.value_used? : false
  when :for
    # `for var in enum; body; end`
    # (for <var> <enum> <body>)
    index == 2 ? parent.value_used? : true
  when :case, :if
    # (case <condition> <when...>)
    # (if <condition> <truebranch> <falsebranch>)
    index == 0 ? true : parent.value_used?
  when :while, :until, :while_post, :until_post
    # (while <condition> <body>) -> always evaluates to `nil`
    index == 0
  else
    true
  end
end
variable?() click to toggle source
# File lib/rubocop/ast_node.rb, line 434
def variable?
  VARIABLES.include?(type)
end

Protected Instance Methods

parent=(node) click to toggle source
# File lib/rubocop/ast_node.rb, line 89
def parent=(node)
  @mutable_attributes[:parent] = node
end
visit_descendants() { |child| ... } click to toggle source
# File lib/rubocop/ast_node.rb, line 556
def visit_descendants(&block)
  children.each do |child|
    next unless child.is_a?(Node)
    yield child
    child.visit_descendants(&block)
  end
end
visit_descendants_with_types(types) { |child| ... } click to toggle source
# File lib/rubocop/ast_node.rb, line 564
def visit_descendants_with_types(types, &block)
  children.each do |child|
    next unless child.is_a?(Node)
    yield child if types.include?(child.type)
    child.visit_descendants_with_types(types, &block)
  end
end

Private Instance Methods

visit_ancestors() { |current_node| ... } click to toggle source
# File lib/rubocop/ast_node.rb, line 574
def visit_ancestors
  last_node = self

  while (current_node = last_node.parent)
    yield current_node
    last_node = current_node
  end
end
visit_ancestors_with_types(types) { |current_node| ... } click to toggle source
# File lib/rubocop/ast_node.rb, line 583
def visit_ancestors_with_types(types)
  last_node = self

  while (current_node = last_node.parent)
    yield current_node if types.include?(current_node.type)
    last_node = current_node
  end
end