Module: Rubocop::Cop::VariableInspector

Included in:
Lint::ShadowingOuterLocalVariable, Lint::UselessAssignment
Defined in:
lib/rubocop/cop/variable_inspector.rb,
lib/rubocop/cop/variable_inspector/scope.rb,
lib/rubocop/cop/variable_inspector/variable.rb,
lib/rubocop/cop/variable_inspector/locatable.rb,
lib/rubocop/cop/variable_inspector/reference.rb,
lib/rubocop/cop/variable_inspector/assignment.rb,
lib/rubocop/cop/variable_inspector/variable_table.rb

Overview

This module provides a way to track local variables and scopes of Ruby. This is intended to be used as mix-in, and the user class may override some of the hook methods.

Defined Under Namespace

Modules: Locatable Classes: Assignment, Reference, Scope, Variable, VariableTable

Constant Summary collapse

VARIABLE_ASSIGNMENT_TYPE = 
:lvasgn
REGEXP_NAMED_CAPTURE_TYPE = 
:match_with_lvasgn
VARIABLE_ASSIGNMENT_TYPES = 
[VARIABLE_ASSIGNMENT_TYPE, REGEXP_NAMED_CAPTURE_TYPE].freeze
METHOD_ARGUMENT_DECLARATION_TYPES = 
[
  :arg, :optarg, :restarg,
  :kwarg, :kwoptarg, :kwrestarg
].freeze
BLOCK_ARGUMENT_DECLARATION_TYPE = 
:blockarg
ARGUMENT_DECLARATION_TYPES = 
(
  METHOD_ARGUMENT_DECLARATION_TYPES + [BLOCK_ARGUMENT_DECLARATION_TYPE]
).freeze
BLOCK_LOCAL_VARIABLE_DECLARATION_TYPE = 
:shadowarg
DECLARATION_TYPES = 
(
  ARGUMENT_DECLARATION_TYPES + [BLOCK_LOCAL_VARIABLE_DECLARATION_TYPE]
).freeze
LOGICAL_OPERATOR_ASSIGNMENT_TYPES = 
[:or_asgn, :and_asgn].freeze
OPERATOR_ASSIGNMENT_TYPES = 
(LOGICAL_OPERATOR_ASSIGNMENT_TYPES + [:op_asgn]).freeze
MULTIPLE_ASSIGNMENT_TYPE = 
:masgn
VARIABLE_REFERENCE_TYPE = 
:lvar
POST_CONDITION_LOOP_TYPES = 
[:while_post, :until_post].freeze
LOOP_TYPES = 
(POST_CONDITION_LOOP_TYPES + [:while, :until, :for]).freeze
RESCUE_TYPE = 
:rescue
ZERO_ARITY_SUPER_TYPE = 
:zsuper
TWISTED_SCOPE_TYPES = 
[:block, :class, :sclass, :defs].freeze
SCOPE_TYPES = 
(TWISTED_SCOPE_TYPES + [:top_level, :module, :def]).freeze

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.wrap_with_top_level_node(node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 59

def wrap_with_top_level_node(node)
  # This is a custom node type, not defined in Parser.
  Parser::AST::Node.new(:top_level, [node])
end

Instance Method Details

#after_declaring_variable(variable_variable) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 359

def after_declaring_variable(variable_variable)
end

#after_entering_scope(scope) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 347

def after_entering_scope(scope)
end

#after_leaving_scope(scope) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 353

def after_leaving_scope(scope)
end

#before_declaring_variable(variable_variable) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 356

def before_declaring_variable(variable_variable)
end

#before_entering_scope(scope) ⇒ Object

Hooks



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# File 'lib/rubocop/cop/variable_inspector.rb', line 344

def before_entering_scope(scope)
end

#before_leaving_scope(scope) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 350

def before_leaving_scope(scope)
end

#dispatch_node(node) ⇒ Object

rubocop:disable MethodLength, CyclomaticComplexity



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# File 'lib/rubocop/cop/variable_inspector.rb', line 93

def dispatch_node(node)
  case node.type
  when *DECLARATION_TYPES
    process_variable_declaration(node)
  when VARIABLE_ASSIGNMENT_TYPE
    process_variable_assignment(node)
  when REGEXP_NAMED_CAPTURE_TYPE
    process_regexp_named_captures(node)
  when *OPERATOR_ASSIGNMENT_TYPES
    process_variable_operator_assignment(node)
  when MULTIPLE_ASSIGNMENT_TYPE
    process_variable_multiple_assignment(node)
  when VARIABLE_REFERENCE_TYPE
    process_variable_referencing(node)
  when *LOOP_TYPES
    process_loop(node)
  when RESCUE_TYPE
    process_rescue(node)
  when ZERO_ARITY_SUPER_TYPE
    process_zero_arity_super(node)
  when *SCOPE_TYPES
    process_scope(node)
  end
end

#find_variables_in_loop(loop_node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 298

def find_variables_in_loop(loop_node)
  referenced_variable_names_in_loop = []
  assignment_nodes_in_loop = []

  # #scan does not consider scope,
  # but we don't need to care about it here.
  scan(loop_node) do |node|
    case node.type
    when :lvar
      referenced_variable_names_in_loop << node.children.first
    when *OPERATOR_ASSIGNMENT_TYPES
      asgn_node = node.children.first
      if asgn_node.type == :lvasgn
        referenced_variable_names_in_loop << asgn_node.children.first
      end
    when :lvasgn
      assignment_nodes_in_loop << node
    end
  end

  [referenced_variable_names_in_loop, assignment_nodes_in_loop]
end

#inspect_variables(root_node) ⇒ Object

Starting point.



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# File 'lib/rubocop/cop/variable_inspector.rb', line 50

def inspect_variables(root_node)
  return unless root_node

  # Wrap the root node with :top_level scope node.
  top_level_node = wrap_with_top_level_node(root_node)

  inspect_variables_in_scope(top_level_node)
end

#inspect_variables_in_scope(scope_node) ⇒ Object

This is called for each scope recursively.



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# File 'lib/rubocop/cop/variable_inspector.rb', line 67

def inspect_variables_in_scope(scope_node)
  variable_table.push_scope(scope_node)
  process_children(scope_node)
  variable_table.pop_scope
end

#mark_assignments_as_referenced_in_loop(node) ⇒ Object

Mark all assignments which are referenced in the same loop as referenced by ignoring AST order since they would be referenced in next iteration.



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# File 'lib/rubocop/cop/variable_inspector.rb', line 280

def mark_assignments_as_referenced_in_loop(node)
  referenced_variable_names_in_loop, assignment_nodes_in_loop =
    find_variables_in_loop(node)

  referenced_variable_names_in_loop.each do |name|
    variable = variable_table.find_variable(name)
    # Non related references which are catched in the above scan
    # would be skipped here.
    next unless variable
    variable.assignments.each do |assignment|
      next if assignment_nodes_in_loop.none? do |assignment_node|
                assignment_node.equal?(assignment.node)
              end
      assignment.reference!
    end
  end
end

#process_children(origin_node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 73

def process_children(origin_node)
  origin_node.children.each do |child|
    next unless child.is_a?(Parser::AST::Node)
    next if scanned_node?(child)
    process_node(child)
  end
end

#process_loop(node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 222

def process_loop(node)
  if POST_CONDITION_LOOP_TYPES.include?(node.type)
    # See the comment at the end of file for this behavior.
    condition_node, body_node = *node
    process_node(body_node)
    process_node(condition_node)
  else
    process_children(node)
  end

  mark_assignments_as_referenced_in_loop(node)

  skip_children!
end

#process_node(node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 81

def process_node(node)
  catch(:skip_children) do
    dispatch_node(node)
    process_children(node)
  end
end

#process_regexp_named_captures(node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 150

def process_regexp_named_captures(node)
  regexp_node, rhs_node = *node

  regexp_string = regexp_node.children[0].children[0]
  regexp = Regexp.new(regexp_string)
  variable_names = regexp.named_captures.keys

  variable_names.each do |name|
    unless variable_table.variable_exist?(name)
      variable_table.declare_variable(name, node)
    end
  end

  process_node(rhs_node)
  process_node(regexp_node)

  variable_names.each do |name|
    variable_table.assign_to_variable(name, node)
  end

  skip_children!
end

#process_rescue(node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 237

def process_rescue(node)
  resbody_nodes = node.children.select do |child|
    next false unless child.is_a?(Parser::AST::Node)
    child.type == :resbody
  end

  contain_retry = resbody_nodes.any? do |resbody_node|
    scan(resbody_node) do |node_in_resbody|
      break true if node_in_resbody.type == :retry
    end
  end

  # Treat begin..rescue..end with retry as a loop.
  process_loop(node) if contain_retry
end

#process_scope(node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 260

def process_scope(node)
  if TWISTED_SCOPE_TYPES.include?(node.type)
    # See the comment at the end of file for this behavior.
    twisted_nodes = [node.children[0]]
    twisted_nodes << node.children[1] if node.type == :class
    twisted_nodes.compact!

    twisted_nodes.each do |twisted_node|
      process_node(twisted_node)
      scanned_nodes << twisted_node
    end
  end

  inspect_variables_in_scope(node)
  skip_children!
end

#process_variable_assignment(node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 130

def process_variable_assignment(node)
  name = node.children.first

  unless variable_table.variable_exist?(name)
    variable_table.declare_variable(name, node)
  end

  # Need to scan rhs before assignment so that we can mark previous
  # assignments as referenced if rhs has referencing to the variable
  # itself like:
  #
  #   foo = 1
  #   foo = foo + 1
  process_children(node)

  variable_table.assign_to_variable(name, node)

  skip_children!
end

#process_variable_declaration(node) ⇒ Object

rubocop:enable MethodLength, CyclomaticComplexity



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# File 'lib/rubocop/cop/variable_inspector.rb', line 119

def process_variable_declaration(node)
  # restarg would have no name:
  #
  #   def initialize(*)
  #   end
  return if node.type == :restarg && node.children.empty?

  variable_name = node.children.first
  variable_table.declare_variable(variable_name, node)
end

#process_variable_multiple_assignment(node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 210

def process_variable_multiple_assignment(node)
  lhs_node, rhs_node = *node
  process_node(rhs_node)
  process_node(lhs_node)
  skip_children!
end

#process_variable_operator_assignment(node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 173

def process_variable_operator_assignment(node)
  if LOGICAL_OPERATOR_ASSIGNMENT_TYPES.include?(node.type)
    asgn_node, rhs_node = *node
  else
    asgn_node, _operator, rhs_node = *node
  end

  return unless asgn_node.type == :lvasgn

  name = asgn_node.children.first

  unless variable_table.variable_exist?(name)
    variable_table.declare_variable(name, asgn_node)
  end

  # The following statements:
  #
  #   foo = 1
  #   foo += foo = 2
  #   # => 3
  #
  # are equivalent to:
  #
  #   foo = 1
  #   foo = foo + (foo = 2)
  #   # => 3
  #
  # So, at operator assignment node, we need to reference the variable
  # before processing rhs nodes.

  variable_table.reference_variable(name, node)
  process_node(rhs_node)
  variable_table.assign_to_variable(name, asgn_node)

  skip_children!
end

#process_variable_referencing(node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 217

def process_variable_referencing(node)
  name = node.children.first
  variable_table.reference_variable(name, node)
end

#process_zero_arity_super(node) ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 253

def process_zero_arity_super(node)
  variable_table.accessible_variables.each do |variable|
    next unless variable.method_argument?
    variable.reference!(node)
  end
end

#scan(node, &block) ⇒ Object

Simple recursive scan



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# File 'lib/rubocop/cop/variable_inspector.rb', line 322

def scan(node, &block)
  node.children.each do |child|
    next unless child.is_a?(Parser::AST::Node)
    yield child
    scan(child, &block)
  end
  nil
end

#scanned_node?(node) ⇒ Boolean

Use Node#equal? for accurate check.

Returns:

  • (Boolean) 


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# File 'lib/rubocop/cop/variable_inspector.rb', line 332

def scanned_node?(node)
  scanned_nodes.any? do |scanned_node|
    scanned_node.equal?(node)
  end
end

#scanned_nodes ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 338

def scanned_nodes
  @scanned_nodes ||= []
end

#skip_children! ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 88

def skip_children!
  throw :skip_children
end

#variable_table ⇒ Object 



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# File 'lib/rubocop/cop/variable_inspector.rb', line 45

def variable_table
  @variable_table ||= VariableTable.new(self)
end