Add Design-At-Version Graph-QL type

Also adds design-fields specs

Note that until we mount this type, we cannot use the mechanism
`GitlabSchema.types[name]` to describe the type in tests

ee/app/graphql/types/design_management/design_at_version_type.rb

+# frozen_string_literal: true
+
+module Types
+  module DesignManagement
+    class DesignAtVersionType < BaseObject
+      graphql_name 'DesignAtVersion'
+
+      description 'A design pinned to a specific version'
+
+      authorize :read_design
+
+      delegate :design, :version, to: :object
+      delegate :issue, :filename, :full_path, :diff_refs, to: :design
+
+      implements ::Types::DesignManagement::DesignFields
+
+      field :version,
+            Types::DesignManagement::VersionType,
+            null: false,
+            description: 'The version this design-at-versions is pinned to'
+
+      field :design,
+            Types::DesignManagement::DesignType,
+            null: false,
+            description: 'The underlying design.'
+
+      def cached_stateful_version(_parent)
+        version
+      end
+
+      def notes_count
+        design.user_notes_count
+      end
+    end
+  end
+end

ee/app/graphql/types/design_management/design_fields.rb

+# frozen_string_literal: true
+
+module Types
+  module DesignManagement
+    module DesignFields
+      include BaseInterface
+
+      field_class Types::BaseField
+
+      field :id, GraphQL::ID_TYPE, description: 'The ID of this design', null: false
+      field :project, Types::ProjectType, null: false, description: 'The project the design belongs to'
+      field :issue, Types::IssueType, null: false, description: 'The issue the design belongs to'
+      field :filename, GraphQL::STRING_TYPE, null: false, description: 'The filename of the design'
+      field :full_path, GraphQL::STRING_TYPE, null: false, description: 'The full path to the design file'
+      field :image, GraphQL::STRING_TYPE, null: false, extras: [:parent], description: 'The URL of the image'
+      field :diff_refs, Types::DiffRefsType,
+            null: false,
+            calls_gitaly: true,
+            extras: [:parent],
+            description: 'The diff refs for this design'
+      field :event, Types::DesignManagement::DesignVersionEventEnum,
+            null: false,
+            extras: [:parent],
+            description: 'How this design was changed in the current version'
+      field :notes_count,
+            GraphQL::INT_TYPE,
+            null: false,
+            method: :user_notes_count,
+            description: 'The total count of user-created notes for this design'
+
+      def diff_refs(parent:)
+        version = cached_stateful_version(parent)
+        version.diff_refs
+      end
+
+      def image(parent:)
+        sha = cached_stateful_version(parent).sha
+
+        ::Gitlab::Routing.url_helpers.project_design_url(design.project, design, sha)
+      end
+
+      def event(parent:)
+        version = cached_stateful_version(parent)
+
+        action = cached_actions_for_version(version)[design.id]
+
+        action&.event || ::Types::DesignManagement::DesignVersionEventEnum::NONE
+      end
+
+      def cached_actions_for_version(version)
+        Gitlab::SafeRequestStore.fetch(['DesignFields', 'actions_for_version', version.id]) do
+          version.actions.to_h { |dv| [dv.design_id, dv] }
+        end
+      end
+
+      def project
+        ::Gitlab::Graphql::Loaders::BatchModelLoader.new(::Project, design.project_id).find
+      end
+
+      def issue
+        ::Gitlab::Graphql::Loaders::BatchModelLoader.new(::Issue, design.issue_id).find
+      end
+    end
+  end
+end

ee/app/graphql/types/design_management/design_type.rb

@@ -7,53 +7,17 @@ module Types
 
       authorize :read_design
 
-      implements(Types::Notes::NoteableType)
-
       alias_method :design, :object
 
-      field :id, GraphQL::ID_TYPE, null: false,
-            description: 'ID of the design'
-      field :project, Types::ProjectType, null: false,
-            description: 'Project associated with the design'
-      field :issue, Types::IssueType, null: false,
-            description: 'Issue associated with the design'
-      field :notes_count, GraphQL::INT_TYPE, null: false,
-            method: :user_notes_count,
-            description: 'Total count of user-created notes for the design'
-      field :filename, GraphQL::STRING_TYPE, null: false,
-            description: 'Filename of the design file'
-      field :full_path, GraphQL::STRING_TYPE, null: false,
-            description: 'Full path of the design file'
-      field :event, Types::DesignManagement::DesignVersionEventEnum, null: false,
-            description: 'Type of change made to the design at the version specified by the `atVersion` argument '\
-                         'if supplied. Defaults to the latest version',
-            extras: [:parent]
-      field :image, GraphQL::STRING_TYPE, null: false,
-            description: 'Image of the design',
-            extras: [:parent]
-      field :diff_refs, Types::DiffRefsType, null: false,
-            description: 'Diff refs of the design',
-            calls_gitaly: true
+      implements(Types::Notes::NoteableType)
+      implements(Types::DesignManagement::DesignFields)
+
       field :versions,
             Types::DesignManagement::VersionType.connection_type,
             resolver: Resolvers::DesignManagement::VersionResolver,
-            description: 'All versions related to the design, ordered newest first',
+            description: "All versions related to this design ordered newest first",
             extras: [:parent]
 
-      def image(parent:)
-        sha = cached_stateful_version(parent).sha
-
-        Gitlab::Routing.url_helpers.project_design_url(design.project, design, sha)
-      end
-
-      def event(parent:)
-        version = cached_stateful_version(parent)
-
-        action = cached_actions_for_version(version)[design.id]
-
-        action&.event || Types::DesignManagement::DesignVersionEventEnum::NONE
-      end
-
       # Returns a `DesignManagement::Version` for this query based on the
       # `atVersion` argument passed to a parent node if present, or otherwise
       # the most recent `Version` for the issue.
@@ -71,12 +35,6 @@ module Types
         end
       end
 
-      def cached_actions_for_version(version)
-        Gitlab::SafeRequestStore.fetch([request_cache_base_key, 'actions_for_version', version.id]) do
-          version.actions.to_h { |dv| [dv.design_id, dv] }
-        end
-      end
-
       def request_cache_base_key
         self.class.name
       end

ee/spec/graphql/types/design_management/design_at_version_type_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+# describe GitlabSchema.types['DesignAtVersion'] do
+# This not available on the schema until we mount it somewhere
+describe ::Types::DesignManagement::DesignAtVersionType.to_graphql do
+  it_behaves_like 'a GraphQL type with design fields' do
+    let(:extra_design_fields) { %i[version design] }
+  end
+end

ee/spec/graphql/types/design_management/design_type_spec.rb

@@ -3,26 +3,7 @@
 require 'spec_helper'
 
 describe GitlabSchema.types['Design'] do
-  it { expect(described_class).to require_graphql_authorizations(:read_design) }
-
-  it { expect(described_class.interfaces).to include(Types::Notes::NoteableType.to_graphql) }
-
-  it 'exposes the expected fields' do
-    expected_fields = %i[
-      diff_refs
-      discussions
-      event
-      filename
-      full_path
-      id
-      image
-      issue
-      notes
-      notes_count
-      project
-      versions
-    ]
-
-    is_expected.to have_graphql_fields(*expected_fields)
+  it_behaves_like 'a GraphQL type with design fields' do
+    let(:extra_design_fields) { %i[notes discussions versions] }
   end
 end

ee/spec/support/shared_examples/design_fields.rb

+# frozen_string_literal: true
+
+shared_examples 'a GraphQL type with design fields' do
+  it { expect(described_class).to require_graphql_authorizations(:read_design) }
+
+  it 'exposes the expected design fields' do
+    expected_fields = %i[
+      id
+      project
+      issue
+      filename
+      full_path
+      image
+      diff_refs
+      event
+      notes_count
+    ] + extra_design_fields
+
+    is_expected.to have_graphql_fields(*expected_fields)
+  end
+end