1 files changed, 99 insertions, 0 deletions
diff --git a/rubocop/cop/gitlab/feature_available_usage.rb b/rubocop/cop/gitlab/feature_available_usage.rb
new file mode 100644
index 00000000000..b50bdd8ca43
--- /dev/null
+++ b/rubocop/cop/gitlab/feature_available_usage.rb
@@ -0,0 +1,99 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Gitlab
+      # Cop that checks for correct calling of #feature_available?
+      class FeatureAvailableUsage < RuboCop::Cop::Cop
+        OBSERVED_METHOD = :feature_available?
+        LICENSED_FEATURE_LITERAL_ARG_MSG = '`feature_available?` should not be called for features that can be licensed (`%s` given), use `licensed_feature_available?(feature)` instead.'
+        LICENSED_FEATURE_DYNAMIC_ARG_MSG = "`feature_available?` should not be called for features that can be licensed (`%s` isn't a literal so we cannot say if it's legit or not), using `licensed_feature_available?(feature)` may be more appropriate."
+        NOT_ENOUGH_ARGS_MSG = '`feature_available?` should be called with two arguments: `feature` and `user`.'
+        FEATURES = %i[
+          issues
+          forking
+          merge_requests
+          wiki
+          snippets
+          builds
+          repository
+          pages
+          metrics_dashboard
+          analytics
+          operations
+          security_and_compliance
+          container_registry
+        ].freeze
+        EE_FEATURES = %i[requirements].freeze
+        ALL_FEATURES = (FEATURES + EE_FEATURES).freeze
+        SPECIAL_CLASS = %w[License].freeze
+
+        def on_send(node)
+          return unless method_name(node) == OBSERVED_METHOD
+          return if caller_is_special_case?(node)
+          return if feature_name(node).nil?
+          return if ALL_FEATURES.include?(feature_name(node)) && args_count(node) == 2
+
+          if !ALL_FEATURES.include?(feature_name(node))
+            add_offense(node, location: :expression, message: licensed_feature_message(node))
+          elsif args_count(node) < 2
+            add_offense(node, location: :expression, message: NOT_ENOUGH_ARGS_MSG)
+          end
+        end
+
+        def licensed_feature_message(node)
+          message_template = dynamic_feature?(node) ? LICENSED_FEATURE_DYNAMIC_ARG_MSG : LICENSED_FEATURE_LITERAL_ARG_MSG
+
+          message_template % feature_arg_name(node)
+        end
+
+        private
+
+        def method_name(node)
+          node.children[1]
+        end
+
+        def class_caller(node)
+          node.children[0]&.const_name.to_s
+        end
+
+        def caller_is_special_case?(node)
+          SPECIAL_CLASS.include?(class_caller(node))
+        end
+
+        def feature_arg(node)
+          node.children[2]
+        end
+
+        def dynamic_feature?(node)
+          feature = feature_arg(node)
+          return false unless feature
+
+          !feature.literal?
+        end
+
+        def feature_name(node)
+          feature = feature_arg(node)
+          return unless feature
+          return feature.children.compact.join('.') if dynamic_feature?(node)
+          return feature.value if feature.respond_to?(:value)
+
+          feature.type
+        end
+
+        def feature_arg_name(node)
+          feature = feature_arg(node)
+          return unless feature
+          return feature.children.compact.join('.') if dynamic_feature?(node)
+          return feature.children[0].inspect if feature.literal?
+
+          feature.type
+        end
+
+        def args_count(node)
+          node.children[2..].size
+        end
+      end
+    end
+  end
+end