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
# 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
@see rubydoc.info/gems/ast/AST/Node:initialize
# 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
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
# 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
# File lib/rubocop/ast_node.rb, line 396 def basic_literal? BASIC_LITERALS.include?(type) end
# 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
# 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
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
# File lib/rubocop/ast_node.rb, line 93 def complete! @mutable_attributes.freeze each_child_node(&:complete!) end
# File lib/rubocop/ast_node.rb, line 98 def complete? @mutable_attributes.frozen? end
# 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
# File lib/rubocop/ast_node.rb, line 309 def defined_module namespace, name = *defined_module0 s(:const, namespace, name) if name end
# File lib/rubocop/ast_node.rb, line 314 def defined_module_name (const = defined_module) && const.const_name end
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
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
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
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
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
# File lib/rubocop/ast_node.rb, line 404 def falsey_literal? FALSEY_LITERALS.include?(type) end
# File lib/rubocop/ast_node.rb, line 412 def immutable_literal? IMMUTABLE_LITERALS.include?(type) end
# 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
# 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
# File lib/rubocop/ast_node.rb, line 392 def literal? LITERALS.include?(type) end
Predicates
# File lib/rubocop/ast_node.rb, line 374 def multiline? expr = loc.expression expr && (expr.first_line != expr.last_line) end
# File lib/rubocop/ast_node.rb, line 408 def mutable_literal? MUTABLE_LITERALS.include?(type) end
# 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
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
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
# 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
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
# File lib/rubocop/ast_node.rb, line 438 def reference? REFERENCES.include?(type) end
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
# File lib/rubocop/ast_node.rb, line 379 def single_line? !multiline? end
# File lib/rubocop/ast_node.rb, line 274 def source loc.expression.source end
# File lib/rubocop/ast_node.rb, line 278 def source_range loc.expression end
# File lib/rubocop/ast_node.rb, line 449 def special_keyword? SPECIAL_KEYWORDS.include?(source) end
# File lib/rubocop/ast_node.rb, line 400 def truthy_literal? TRUTHY_LITERALS.include?(type) end
# 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
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
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
# File lib/rubocop/ast_node.rb, line 434 def variable? VARIABLES.include?(type) end
Protected Instance Methods
# File lib/rubocop/ast_node.rb, line 89 def parent=(node) @mutable_attributes[:parent] = node end
# 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
# 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
# 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
# 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