Add `present_using` to types

By specifying a presenter for the object type, we can keep the logic
out of `GitlabSchema`.

The presenter gets initialized using the object being presented, and
the context (including the `current_user`).

1 files changed, 34 insertions, 0 deletions

diff --git a/lib/gitlab/graphql/present.rb b/lib/gitlab/graphql/present.rb
new file mode 100644
index 00000000000..b060692b334
--- /dev/null
+++ b/lib/gitlab/graphql/present.rb
@@ -0,0 +1,34 @@
+module Gitlab
+  module Graphql
+    class Present
+      PRESENT_USING = -> (type, presenter_class, *args) do
+        type.metadata[:presenter_class] = presenter_class
+      end
+
+      INSTRUMENT_PROC = -> (schema) do
+        schema.instrument(:field, new)
+      end
+
+      def self.register!
+        GraphQL::Schema.accepts_definitions(enable_presenting: INSTRUMENT_PROC)
+        GraphQL::ObjectType.accepts_definitions(present_using: PRESENT_USING)
+      end
+
+      def instrument(type, field)
+        return field unless type.metadata[:presenter_class]
+
+        old_resolver = field.resolve_proc
+
+        resolve_with_presenter = -> (obj, args, context) do
+          presenter = type.metadata[:presenter_class].new(obj, **context.to_h)
+
+          old_resolver.call(presenter, args, context)
+        end
+
+        field.redefine do
+          resolve(resolve_with_presenter)
+        end
+      end
+    end
+  end
+end