1 files changed, 27 insertions, 0 deletions
diff --git a/rubocop/cop/gitlab/union.rb b/rubocop/cop/gitlab/union.rb
new file mode 100644
index 00000000000..09541d8af3b
--- /dev/null
+++ b/rubocop/cop/gitlab/union.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+require_relative '../../spec_helpers'
+
+module RuboCop
+  module Cop
+    module Gitlab
+      # Cop that disallows the use of `Gitlab::SQL::Union`, in favour of using
+      # the `FromUnion` module.
+      class Union < RuboCop::Cop::Cop
+        include SpecHelpers
+
+        MSG = 'Use the `FromUnion` concern, instead of using `Gitlab::SQL::Union` directly'
+
+        def_node_matcher :raw_union?, <<~PATTERN
+          (send (const (const (const nil? :Gitlab) :SQL) :Union) :new ...)
+        PATTERN
+
+        def on_send(node)
+          return unless raw_union?(node)
+          return if in_spec?(node)
+
+          add_offense(node, location: :expression)
+        end
+      end
+    end
+  end
+end