1 files changed, 67 insertions, 0 deletions
diff --git a/rubocop/cop/rspec/factory_bot/local_static_assignment.rb b/rubocop/cop/rspec/factory_bot/local_static_assignment.rb
new file mode 100644
index 00000000000..1a26bc31c78
--- /dev/null
+++ b/rubocop/cop/rspec/factory_bot/local_static_assignment.rb
@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+require 'rubocop-rspec'
+
+module RuboCop
+  module Cop
+    module RSpec
+      module FactoryBot
+        # Flags local assignments during factory "load time". This leads to
+        # static data definitions.
+        #
+        # Move these definitions into attribute block or
+        # `transient` block to ensure that the data is evaluated during
+        # "runtime" and remains dynamic.
+        #
+        # @example
+        #   # bad
+        #   factory :foo do
+        #     random = rand(23)
+        #     baz { "baz-#{random}" }
+        #
+        #     trait :a_trait do
+        #       random = rand(23)
+        #       baz { "baz-#{random}" }
+        #     end
+        #
+        #     transient do
+        #       random = rand(23)
+        #       baz { "baz-#{random}" }
+        #     end
+        #   end
+        #
+        #   # good
+        #   factory :foo do
+        #     baz { "baz-#{random}" }
+        #
+        #     trait :a_trait do
+        #       baz { "baz-#{random}" }
+        #     end
+        #
+        #     transient do
+        #       random { rand(23) }
+        #     end
+        #   end
+        class LocalStaticAssignment < RuboCop::Cop::Base
+          MSG = 'Avoid local static assignemnts in factories which lead to static data definitions.'
+
+          RESTRICT_ON_SEND = %i[factory transient trait].freeze
+
+          def_node_search :local_assignment, <<~PATTERN
+            (begin $(lvasgn ...))
+          PATTERN
+
+          def on_send(node)
+            return unless node.parent&.block_type?
+
+            node.parent.each_child_node(:begin) do |begin_node|
+              begin_node.each_child_node(:lvasgn) do |lvasgn_node|
+                add_offense(lvasgn_node)
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end