Class: RuboCop::Node

Inherits:
Parser::AST::Node
  • Object
show all
Includes:
Sexp
Defined in:
lib/rubocop/ast_node.rb,
lib/rubocop/ast_node/builder.rb,
lib/rubocop/ast_node/traversal.rb

Overview

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:

Examples:

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?)

Defined Under Namespace

Modules: Traversal Classes: Builder

Constant Summary collapse

COMPARISON_OPERATORS = 
[:!, :==, :===, :!=, :<=, :>=, :>, :<, :<=>].freeze
TRUTHY_LITERALS = 
[:str, :dstr, :xstr, :int, :float, :sym, :dsym, :array,
:hash, :regexp, :true, :irange, :erange, :complex,
:rational, :regopt].freeze
FALSEY_LITERALS = 
[:false, :nil].freeze
LITERALS = 
(TRUTHY_LITERALS + FALSEY_LITERALS).freeze
COMPOSITE_LITERALS = 
[:dstr, :xstr, :dsym, :array, :hash, :irange,
:erange, :regexp].freeze
BASIC_LITERALS = 
(LITERALS - COMPOSITE_LITERALS).freeze
MUTABLE_LITERALS = 
[:str, :dstr, :xstr, :array, :hash].freeze
IMMUTABLE_LITERALS = 
(LITERALS - MUTABLE_LITERALS).freeze
VARIABLES = 
[:ivar, :gvar, :cvar, :lvar].freeze
REFERENCES = 
[:nth_ref, :back_ref].freeze
KEYWORDS = 
[:alias, :and, :break, :case, :class, :def, :defs, :defined?,
:kwbegin, :do, :else, :ensure, :for, :if, :module, :next, :not,
:or, :postexe, :redo, :rescue, :retry, :return, :self, :super,
:zsuper, :then, :undef, :until, :when, :while, :yield].freeze
OPERATOR_KEYWORDS = 
[:and, :or].freeze
SPECIAL_KEYWORDS = 
%w(__FILE__ __LINE__ __ENCODING__).freeze
RSPEC_METHODS = 
[:describe, :it].freeze

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Sexp

#s

Constructor Details

#initialize(type, children = [], properties = {}) ⇒ Node

Returns a new instance of Node.

See Also:



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# File 'lib/rubocop/ast_node.rb', line 62

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

Class Method Details

.def_matcher(method_name, pattern_str) ⇒ Object 



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# File 'lib/rubocop/ast_node.rb', line 50

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

Instance Method Details

#ancestors ⇒ Array<Node>

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

Returns:

  • (Array<Node>) —

    an array of ancestor nodes



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# File 'lib/rubocop/ast_node.rb', line 159

def ancestors
  each_ancestor.to_a
end

#asgn_method_call? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 362

def asgn_method_call?
  !COMPARISON_OPERATORS.include?(method_name) &&
    method_name.to_s.end_with?('='.freeze)
end

#basic_literal? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 375

def basic_literal?
  BASIC_LITERALS.include?(type)
end

#chained? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 443

def chained?
  return false if parent.nil? || !parent.send_type?
  receiver, _method_name, *_args = *parent
  equal?(receiver)
end

#child_nodes ⇒ Array<Node>

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

Returns:

  • (Array<Node>) —

    an array of child nodes



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# File 'lib/rubocop/ast_node.rb', line 199

def child_nodes
  each_child_node.to_a
end

#complete! ⇒ Object 



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# File 'lib/rubocop/ast_node.rb', line 96

def complete!
  @mutable_attributes.freeze
  each_child_node(&:complete!)
end

#complete? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 101

def complete?
  @mutable_attributes.frozen?
end

#const_name ⇒ Object 



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# File 'lib/rubocop/ast_node.rb', line 294

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 ⇒ Object 



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# File 'lib/rubocop/ast_node.rb', line 312

def defined_module
  namespace, name = *defined_module0
  s(:const, namespace, name) if name
end

#defined_module_name ⇒ Object 



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# File 'lib/rubocop/ast_node.rb', line 317

def defined_module_name
  (const = defined_module) && const.const_name
end

#descendants ⇒ Array<Node>

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

Returns:

  • (Array<Node>) —

    an array of descendant nodes



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# File 'lib/rubocop/ast_node.rb', line 237

def descendants
  each_descendant.to_a
end

#each_ancestor ⇒ self, Enumerator #each_ancestor(type) ⇒ self, Enumerator #each_ancestor(type_a, type_b, ...) ⇒ self, Enumerator #each_ancestor(types) ⇒ self, Enumerator

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

Overloads:

  • #each_ancestor ⇒ self, Enumerator

    Yield all nodes.

  • #each_ancestor(type) ⇒ self, Enumerator

    Yield only nodes matching the type.

    Parameters:

    • type (Symbol) —

      a node type

  • #each_ancestor(type_a, type_b, ...) ⇒ self, Enumerator

    Yield only nodes matching any of the types.

    Parameters:

    • type_a (Symbol) —

      a node type

    • type_b (Symbol) —

      a node type

  • #each_ancestor(types) ⇒ self, Enumerator

    Yield only nodes matching any of types in the array.

    Parameters:

    • types (Array<Symbol>) —

      an array containing node types

Yield Parameters:

  • node (Node) —

    each ancestor node

Returns:

  • (self) —

    if a block is given

  • (Enumerator) —

    if no block is given



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# File 'lib/rubocop/ast_node.rb', line 143

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 ⇒ self, Enumerator #each_child_node(type) ⇒ self, Enumerator #each_child_node(type_a, type_b, ...) ⇒ self, Enumerator #each_child_node(types) ⇒ self, Enumerator

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.

Overloads:

  • #each_child_node ⇒ self, Enumerator

    Yield all nodes.

  • #each_child_node(type) ⇒ self, Enumerator

    Yield only nodes matching the type.

    Parameters:

    • type (Symbol) —

      a node type

  • #each_child_node(type_a, type_b, ...) ⇒ self, Enumerator

    Yield only nodes matching any of the types.

    Parameters:

    • type_a (Symbol) —

      a node type

    • type_b (Symbol) —

      a node type

  • #each_child_node(types) ⇒ self, Enumerator

    Yield only nodes matching any of types in the array.

    Parameters:

    • types (Array<Symbol>) —

      an array containing node types

Yield Parameters:

  • node (Node) —

    each child node

Returns:

  • (self) —

    if a block is given

  • (Enumerator) —

    if no block is given



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# File 'lib/rubocop/ast_node.rb', line 184

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 ⇒ self, Enumerator #each_descendant(type) ⇒ self, Enumerator #each_descendant(type_a, type_b, ...) ⇒ self, Enumerator #each_descendant(types) ⇒ self, Enumerator

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

Overloads:

  • #each_descendant ⇒ self, Enumerator

    Yield all nodes.

  • #each_descendant(type) ⇒ self, Enumerator

    Yield only nodes matching the type.

    Parameters:

    • type (Symbol) —

      a node type

  • #each_descendant(type_a, type_b, ...) ⇒ self, Enumerator

    Yield only nodes matching any of the types.

    Parameters:

    • type_a (Symbol) —

      a node type

    • type_b (Symbol) —

      a node type

  • #each_descendant(types) ⇒ self, Enumerator

    Yield only nodes matching any of types in the array.

    Parameters:

    • types (Array<Symbol>) —

      an array containing node types

Yield Parameters:

  • node (Node) —

    each descendant node

Returns:

  • (self) —

    if a block is given

  • (Enumerator) —

    if no block is given



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# File 'lib/rubocop/ast_node.rb', line 221

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 ⇒ self, Enumerator #each_node(type) ⇒ self, Enumerator #each_node(type_a, type_b, ...) ⇒ self, Enumerator #each_node(types) ⇒ self, Enumerator

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.

Overloads:

  • #each_node ⇒ self, Enumerator

    Yield all nodes.

  • #each_node(type) ⇒ self, Enumerator

    Yield only nodes matching the type.

    Parameters:

    • type (Symbol) —

      a node type

  • #each_node(type_a, type_b, ...) ⇒ self, Enumerator

    Yield only nodes matching any of the types.

    Parameters:

    • type_a (Symbol) —

      a node type

    • type_b (Symbol) —

      a node type

  • #each_node(types) ⇒ self, Enumerator

    Yield only nodes matching any of types in the array.

    Parameters:

    • types (Array<Symbol>) —

      an array containing node types

Yield Parameters:

  • node (Node) —

    each node

Returns:

  • (self) —

    if a block is given

  • (Enumerator) —

    if no block is given



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# File 'lib/rubocop/ast_node.rb', line 263

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? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 383

def falsey_literal?
  FALSEY_LITERALS.include?(type)
end

#immutable_literal? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 391

def immutable_literal?
  IMMUTABLE_LITERALS.include?(type)
end

#keyword? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 421

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? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 432

def keyword_not?
  _receiver, method_name, *args = *self
  args.empty? && method_name == :! && loc.selector.is?('not'.freeze)
end

#known_dsl? ⇒ Boolean

Known DSL methods which eval body inside an anonymous class/module

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 528

def known_dsl?
  RSPEC_METHODS.include?(method_name) && receiver.nil?
end

#literal? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 371

def literal?
  LITERALS.include?(type)
end

#multiline? ⇒ Boolean

Predicates

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 353

def multiline?
  expr = loc.expression
  expr && (expr.first_line != expr.last_line)
end

#mutable_literal? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 387

def mutable_literal?
  MUTABLE_LITERALS.include?(type)
end

#parent ⇒ Node?

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

Returns:

  • (Node, nil) —

    the parent node or nil



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# File 'lib/rubocop/ast_node.rb', line 88

def parent
  @mutable_attributes[:parent]
end

#parent_module_name ⇒ Object

Searching the AST



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# File 'lib/rubocop/ast_node.rb', line 323

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
      obj = ancestor.children[0]
      # TODO: look for constant definition and see if it is nested
      # inside a class or module
      return "#<Class:#{obj.const_name}>" if obj.const_type?
      return "#<Class:#{ancestor.parent_module_name}>" if obj.self_type?
      return nil
    else # block
      return nil if ancestor.known_dsl?
      if ancestor.method_name == :class_eval && ancestor.receiver
        return nil unless ancestor.receiver.const_type?
        ancestor.receiver.const_name
      end
    end
  end.compact.reverse.join('::')
  result.empty? ? 'Object' : result
end

#pure? ⇒ Boolean

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?

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 512

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

#receiver ⇒ Object

Destructuring



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# File 'lib/rubocop/ast_node.rb', line 287

def_matcher :receiver,    '{(send $_ ...) (block (send $_ ...) ...)}'

#reference? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 417

def reference?
  REFERENCES.include?(type)
end

#sibling_index ⇒ Integer

Returns the index of the receiver node in its siblings.

Returns:

  • (Integer) —

    the index of the receiver node in its siblings



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# File 'lib/rubocop/ast_node.rb', line 121

def sibling_index
  parent.children.index { |sibling| sibling.equal?(self) }
end

#single_line? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 358

def single_line?
  !multiline?
end

#source ⇒ Object 



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# File 'lib/rubocop/ast_node.rb', line 277

def source
  loc.expression.source
end

#source_range ⇒ Object 



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# File 'lib/rubocop/ast_node.rb', line 281

def source_range
  loc.expression
end

#special_keyword? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 428

def special_keyword?
  SPECIAL_KEYWORDS.include?(source)
end

#truthy_literal? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 379

def truthy_literal?
  TRUTHY_LITERALS.include?(type)
end

#unary_operation? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 437

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 = {}) ⇒ Object

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.



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# File 'lib/rubocop/ast_node.rb', line 113

def updated(type = nil, children = nil, properties = {})
  properties[:location] ||= @location
  Node.new(type || @type, children || @children, properties)
end

#value_used? ⇒ Boolean

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?

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 475

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, :block, :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? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/ast_node.rb', line 413

def variable?
  VARIABLES.include?(type)
end