1 files changed, 48 insertions, 0 deletions
diff --git a/spec/support/finder_collection.rb b/spec/support/finder_collection.rb
new file mode 100644
index 00000000000..494dd4bdca1
--- /dev/null
+++ b/spec/support/finder_collection.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+require 'set'
+
+module Support
+  # Ensure that finders' `execute` method always returns
+  # `ActiveRecord::Relation`.
+  #
+  # See https://gitlab.com/gitlab-org/gitlab/-/issues/298771
+  module FinderCollection
+    def self.install_check(finder_class)
+      return unless check?(finder_class)
+
+      finder_class.prepend CheckResult
+    end
+
+    ALLOWLIST_YAML = File.join(__dir__, 'finder_collection_allowlist.yml')
+
+    def self.check?(finder_class)
+      @allowlist ||= YAML.load_file(ALLOWLIST_YAML).to_set
+
+      @allowlist.exclude?(finder_class.name)
+    end
+
+    module CheckResult
+      def execute(...)
+        result = super
+
+        unless result.is_a?(ActiveRecord::Relation)
+          raise <<~MESSAGE
+            #{self.class}#execute returned `#{result.class}` instead of `ActiveRecord::Relation`.
+            All finder classes are expected to return `ActiveRecord::Relation`.
+
+            Read more at https://docs.gitlab.com/ee/development/reusing_abstractions.html#finders
+          MESSAGE
+        end
+
+        result
+      end
+    end
+  end
+end
+
+RSpec.configure do |config|
+  config.before(:all, type: :finder) do
+    Support::FinderCollection.install_check(described_class)
+  end
+end