Expose wiki_size on GraphQL API

app/graphql/types/project_statistics_type.rb

@@ -11,5 +11,6 @@ module Types
     field :lfs_objects_size, GraphQL::INT_TYPE, null: false
     field :build_artifacts_size, GraphQL::INT_TYPE, null: false
     field :packages_size, GraphQL::INT_TYPE, null: false
+    field :wiki_size, GraphQL::INT_TYPE, null: true
   end
 end

changelogs/unreleased/ac-graphql-wikisize.yml

+---
+title: Expose wiki_size on GraphQL API
+merge_request: 29123
+author:
+type: added

spec/graphql/types/project_statistics_type_spec.rb

@@ -5,6 +5,7 @@ require 'spec_helper'
 describe GitlabSchema.types['ProjectStatistics'] do
   it "has all the required fields" do
     is_expected.to have_graphql_fields(:storage_size, :repository_size, :lfs_objects_size,
-                                       :build_artifacts_size, :packages_size, :commit_count)
+                                       :build_artifacts_size, :packages_size, :commit_count,
+                                       :wiki_size)
   end
 end