Add Scalability/FileUploads cop

This cop prevents you from using file in API, it points you to the
development documentation about workhorse file acceleration.

2 files changed, 62 insertions, 0 deletions

diff --git a/rubocop/cop/scalability/file_uploads.rb b/rubocop/cop/scalability/file_uploads.rb
new file mode 100644
index 00000000000..83017217e32
--- /dev/null
+++ b/rubocop/cop/scalability/file_uploads.rb
@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Scalability
+      # This cop checks for `File` params in API
+      #
+      # @example
+      #
+      #   # bad
+      #   params do
+      #     requires :file, type: File
+      #   end
+      #
+      #   params do
+      #     optional :file, type: File
+      #   end
+      #
+      #   # good
+      #   params do
+      #     requires :file, type: ::API::Validations::Types::WorkhorseFile
+      #   end
+      #
+      #   params do
+      #     optional :file, type: ::API::Validations::Types::WorkhorseFile
+      #   end
+      #
+      class FileUploads < RuboCop::Cop::Cop
+        MSG = 'Do not upload files without workhorse acceleration. Please refer to https://docs.gitlab.com/ee/development/uploads.html'
+
+        def_node_search :file_type_params?, <<~PATTERN
+          (send nil? {:requires :optional} (sym _) (hash <(pair (sym :type)(const nil? :File)) ...>))
+        PATTERN
+
+        def_node_search :file_types_params?, <<~PATTERN
+          (send nil? {:requires :optional} (sym _) (hash <(pair (sym :types)(array <(const nil? :File) ...>)) ...>))
+        PATTERN
+
+        def be_file_param_usage?(node)
+          file_type_params?(node) || file_types_params?(node)
+        end
+
+        def on_send(node)
+          return unless be_file_param_usage?(node)
+
+          add_offense(find_file_param(node), location: :expression)
+        end
+
+        private
+
+        def find_file_param(node)
+          node.each_descendant.find { |children| file_node_pattern.match(children) }
+        end
+
+        def file_node_pattern
+          @file_node_pattern ||= RuboCop::NodePattern.new("(const nil? :File)")
+        end
+      end
+    end
+  end
+end
diff --git a/rubocop/rubocop.rb b/rubocop/rubocop.rb
index c342df6d6c9..9d97aa86bf6 100644
--- a/rubocop/rubocop.rb
+++ b/rubocop/rubocop.rb
@@ -37,6 +37,7 @@ require_relative 'cop/rspec/factories_in_migration_specs'
 require_relative 'cop/rspec/top_level_describe_path'
 require_relative 'cop/qa/element_with_pattern'
 require_relative 'cop/sidekiq_options_queue'
+require_relative 'cop/scalability/file_uploads'
 require_relative 'cop/destroy_all'
 require_relative 'cop/ruby_interpolation_in_translation'
 require_relative 'code_reuse_helpers'