instance_variable.rb in rubocop-rspec-1.7.0

- old
+ new

@@ -1,13 +1,17 @@
 # frozen_string_literal: true
 
 module RuboCop
   module Cop
     module RSpec
-      # When you have to assign a variable instead of using an instance
-      # variable, use let.
+      # Checks for instance variable usage in specs.
       #
+      # This cop can be configured with the option `AssignmentOnly` which
+      # will configure the cop to only register offenses on instance
+      # variable usage if the instance variable is also assigned within
+      # the spec
+      #
       # @example
       #   # bad
       #   describe MyClass do
       #     before { @foo = [] }
       #     it { expect(@foo).to be_empty }
@@ -16,25 +20,62 @@
       #   # good
       #   describe MyClass do
       #     let(:foo) { [] }
       #     it { expect(foo).to be_empty }
       #   end
+      #
+      # @example with AssignmentOnly configuration
+      #
+      #   # rubocop.yml
+      #   RSpec/InstanceVariable:
+      #     AssignmentOnly: false
+      #
+      #   # bad
+      #   describe MyClass do
+      #     before { @foo = [] }
+      #     it { expect(@foo).to be_empty }
+      #   end
+      #
+      #   # allowed
+      #   describe MyClass do
+      #     it { expect(@foo).to be_empty }
+      #   end
+      #
+      #   # good
+      #   describe MyClass do
+      #     let(:foo) { [] }
+      #     it { expect(foo).to be_empty }
+      #   end
+      #
       class InstanceVariable < Cop
+        include RuboCop::RSpec::SpecOnly, RuboCop::RSpec::Language
+
         MESSAGE = 'Use `let` instead of an instance variable'.freeze
-        EXAMPLE_GROUP_METHODS = [
-          :example_group, :describe, :context, :xdescribe, :xcontext,
-          :fdescribe, :fcontext, :shared_examples, :shared_context,
-          :share_examples_for, :shared_examples_for, :feature
-        ].freeze
 
+        EXAMPLE_GROUP_METHODS = ExampleGroups::ALL + SharedGroups::ALL
+
+        def_node_matcher :spec_group?, <<-PATTERN
+          (block (send _ {#{EXAMPLE_GROUP_METHODS.to_node_pattern}} ...) ...)
+        PATTERN
+
+        def_node_search :ivar_usage, '$(ivar $_)'
+
+        def_node_search :ivar_assigned?, '(ivasgn % ...)'
+
         def on_block(node)
-          method, _args, _body = *node
-          _receiver, method_name, _object = *method
-          @in_spec = true if EXAMPLE_GROUP_METHODS.include?(method_name)
+          return unless spec_group?(node)
+
+          ivar_usage(node) do |ivar, name|
+            return if assignment_only? && !ivar_assigned?(node, name)
+
+            add_offense(ivar, :expression, MESSAGE)
+          end
         end
 
-        def on_ivar(node)
-          add_offense(node, :expression, MESSAGE) if @in_spec
+        private
+
+        def assignment_only?
+          cop_config['AssignmentOnly']
         end
       end
     end
   end
 end