class RuboCop::Cop::Lint::ConstantReassignment
Checks for constant reassignments.
Emulates Ruby’s runtime warning “already initialized constant X” when a constant is reassigned in the same file and namespace using the ‘NAME = value` syntax.
The cop cannot catch all offenses, like, for example, when a constant is reassigned in another file, or when using metaprogramming (‘Module#const_set`).
The cop only takes into account constants assigned in a “simple” way: directly inside class/module definition, or within another constant. Other type of assignments (e.g., inside a conditional) are disregarded.
The cop also tracks constant removal using ‘Module#remove_const` with symbol or string argument.
@example
# bad X = :foo X = :bar # bad class A X = :foo X = :bar end # bad module A X = :foo X = :bar end # good - keep only one assignment X = :bar class A X = :bar end module A X = :bar end # good - use OR assignment X = :foo X ||= :bar # good - use conditional assignment X = :foo X = :bar unless defined?(X) # good - remove the assigned constant first class A X = :foo remove_const :X X = :bar end
Constants
- MSG
- RESTRICT_ON_SEND
Public Instance Methods
Source
# File lib/rubocop/cop/lint/constant_reassignment.rb, line 76 def on_casgn(node) return unless fixed_constant_path?(node) return unless simple_assignment?(node) return if constant_names.add?(fully_qualified_constant_name(node)) add_offense(node, message: format(MSG, constant: node.name)) end
Source
# File lib/rubocop/cop/lint/constant_reassignment.rb, line 84 def on_send(node) constant = remove_constant(node) return unless constant namespaces = ancestor_namespaces(node) return if namespaces.none? constant_names.delete(fully_qualified_name_for(namespaces, constant)) end
Private Instance Methods
Source
# File lib/rubocop/cop/lint/constant_reassignment.rb, line 135 def ancestor_namespaces(node) node .each_ancestor(:class, :module) .map { |ancestor| ancestor.identifier.short_name } .reverse end
Source
# File lib/rubocop/cop/lint/constant_reassignment.rb, line 142 def constant_names @constant_names ||= Set.new end
Source
# File lib/rubocop/cop/lint/constant_reassignment.rb, line 131 def constant_namespaces(node) node.each_path.select(&:const_type?).map(&:short_name) end
Source
# File lib/rubocop/cop/lint/constant_reassignment.rb, line 98 def fixed_constant_path?(node) node.each_path.all? { |path| path.type?(:cbase, :const, :self) } end
Source
# File lib/rubocop/cop/lint/constant_reassignment.rb, line 111 def freeze_method?(node) node.send_type? && node.method?(:freeze) end
Source
# File lib/rubocop/cop/lint/constant_reassignment.rb, line 115 def fully_qualified_constant_name(node) if node.absolute? namespace = node.namespace.const_type? ? node.namespace.source : nil "#{namespace}::#{node.name}" else constant_namespaces = ancestor_namespaces(node) + constant_namespaces(node) fully_qualified_name_for(constant_namespaces, node.name) end end
Source
# File lib/rubocop/cop/lint/constant_reassignment.rb, line 127 def fully_qualified_name_for(namespaces, constant) ['', *namespaces, constant].join('::') end
Source
# File lib/rubocop/cop/lint/constant_reassignment.rb, line 102 def simple_assignment?(node) node.ancestors.all? do |ancestor| return true if ancestor.type?(:module, :class) ancestor.begin_type? || ancestor.literal? || ancestor.casgn_type? || freeze_method?(ancestor) end end