Resolve "Make a Rubocop that forbids returning from a block"

1 files changed, 48 insertions, 0 deletions

diff --git a/rubocop/cop/avoid_break_from_strong_memoize.rb b/rubocop/cop/avoid_break_from_strong_memoize.rb
new file mode 100644
index 00000000000..9b436118db3
--- /dev/null
+++ b/rubocop/cop/avoid_break_from_strong_memoize.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    # Checks for break inside strong_memoize blocks.
+    # For more information see: https://gitlab.com/gitlab-org/gitlab-ce/issues/42889
+    #
+    # @example
+    #   # bad
+    #   strong_memoize(:result) do
+    #     break if something
+    #
+    #     do_an_heavy_calculation
+    #   end
+    #
+    #   # good
+    #   strong_memoize(:result) do
+    #     next if something
+    #
+    #     do_an_heavy_calculation
+    #   end
+    #
+    class AvoidBreakFromStrongMemoize < RuboCop::Cop::Cop
+      MSG = 'Do not use break inside strong_memoize, use next instead.'
+
+      def on_block(node)
+        block_body = node.body
+
+        return unless block_body
+        return unless node.method_name == :strong_memoize
+
+        block_body.each_node(:break) do |break_node|
+          next if container_block_for(break_node) != node
+
+          add_offense(break_node)
+        end
+      end
+
+      private
+
+      def container_block_for(current_node)
+        current_node = current_node.parent until current_node.type == :block && current_node.method_name == :strong_memoize
+
+        current_node
+      end
+    end
+  end
+end