Performance. RSpec/LetSetup

lib/rubocop/cop/rspec/let_setup.rb

@@ -28,14 +28,20 @@ module RSpec
       class LetSetup < Cop
         MSG = 'Do not use `let!` to setup objects not referenced in tests.'
 
-        def_node_search :let_bang, <<-PATTERN
+        def_node_matcher :example_or_shared_group_or_including?,
+                         (
+                           ExampleGroups::ALL + SharedGroups::ALL +
+                           Includes::ALL
+                         ).block_pattern
+
+        def_node_matcher :let_bang, <<-PATTERN
           (block $(send nil? :let! (sym $_)) args ...)
         PATTERN
 
         def_node_search :method_called?, '(send nil? %)'
 
         def on_block(node)
-          return unless example_group?(node)
+          return unless example_or_shared_group_or_including?(node)
 
           unused_let_bang(node) do |let|
             add_offense(let)
@@ -45,10 +51,16 @@ def on_block(node)
         private
 
         def unused_let_bang(node)
-          let_bang(node) do |method_send, method_name|
+          child_let_bang(node) do |method_send, method_name|
             yield(method_send) unless method_called?(node, method_name)
           end
         end
+
+        def child_let_bang(node, &block)
+          RuboCop::RSpec::ExampleGroup.new(node).lets.each do |let|
+            let_bang(let, &block)
+          end
+        end
       end
     end
   end

spec/rubocop/cop/rspec/let_setup_spec.rb

@@ -63,4 +63,53 @@
       end
     RUBY
   end
+
+  it 'complains when let! is used and not referenced in shared example group' do
+    expect_offense(<<-RUBY)
+      shared_context 'foo' do
+        let!(:bar) { baz }
+        ^^^^^^^^^^ Do not use `let!` to setup objects not referenced in tests.
+
+        it 'does not use bar' do
+          expect(baz).to eq(qux)
+        end
+      end
+    RUBY
+  end
+
+  it 'complains when let! used in shared example including' do
+    expect_offense(<<-RUBY)
+      describe Foo do
+        it_behaves_like 'bar' do
+          let!(:baz) { foobar }
+          ^^^^^^^^^^ Do not use `let!` to setup objects not referenced in tests.
+          let(:a) { b }
+        end
+      end
+    RUBY
+  end
+
+  it 'complains when there is only one nested node into example group' do
+    expect_offense(<<-RUBY)
+      describe Foo do
+        let!(:bar) { baz }
+        ^^^^^^^^^^ Do not use `let!` to setup objects not referenced in tests.
+      end
+    RUBY
+  end
+
+  it 'complains when there is a custom nesting level' do
+    expect_offense(<<-RUBY)
+      describe Foo do
+        [].each do |i|
+          let!(:bar) { i }
+          ^^^^^^^^^^ Do not use `let!` to setup objects not referenced in tests.
+
+          it 'does not use bar' do
+            expect(baz).to eq(qux)
+          end
+        end
+      end
+    RUBY
+  end
 end