Expose namespace storage statistics with GraphQL

Root namespaces have storage statistics.
This commit allows namespace owners to get those stats via GraphQL
queries like the following one

{
  namespace(fullPath: "a_namespace_path") {
    rootStorageStatistics {
      storageSize
      repositorySize
      lfsObjectsSize
      buildArtifactsSize
      packagesSize
      wikiSize
    }
  }
}

9 files changed, 185 insertions, 4 deletions

diff --git a/spec/graphql/types/namespace_type_spec.rb b/spec/graphql/types/namespace_type_spec.rb
index e1153832cc9..f476dd7286f 100644
--- a/spec/graphql/types/namespace_type_spec.rb
+++ b/spec/graphql/types/namespace_type_spec.rb
@@ -8,7 +8,7 @@ describe GitlabSchema.types['Namespace'] do
   it 'has the expected fields' do
     expected_fields = %w[
       id name path full_name full_path description description_html visibility
-      lfs_enabled request_access_enabled projects
+      lfs_enabled request_access_enabled projects root_storage_statistics
     ]
 
     is_expected.to have_graphql_fields(*expected_fields)
diff --git a/spec/graphql/types/root_storage_statistics_type_spec.rb b/spec/graphql/types/root_storage_statistics_type_spec.rb
new file mode 100644
index 00000000000..8c69c13aa73
--- /dev/null
+++ b/spec/graphql/types/root_storage_statistics_type_spec.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe GitlabSchema.types['RootStorageStatistics'] do
+  it { expect(described_class.graphql_name).to eq('RootStorageStatistics') }
+
+  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, :wiki_size)
+  end
+
+  it { is_expected.to require_graphql_authorizations(:read_statistics) }
+end
diff --git a/spec/lib/gitlab/graphql/loaders/batch_root_storage_statistics_loader_spec.rb b/spec/lib/gitlab/graphql/loaders/batch_root_storage_statistics_loader_spec.rb
new file mode 100644
index 00000000000..38931f7ab5e
--- /dev/null
+++ b/spec/lib/gitlab/graphql/loaders/batch_root_storage_statistics_loader_spec.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Graphql::Loaders::BatchRootStorageStatisticsLoader do
+  describe '#find' do
+    it 'only queries once for project statistics' do
+      stats = create_list(:namespace_root_storage_statistics, 2)
+      namespace1 = stats.first.namespace
+      namespace2 = stats.last.namespace
+
+      expect do
+        described_class.new(namespace1.id).find
+        described_class.new(namespace2.id).find
+      end.not_to exceed_query_limit(1)
+    end
+  end
+end
diff --git a/spec/models/namespace/root_storage_statistics_spec.rb b/spec/models/namespace/root_storage_statistics_spec.rb
index 5341278db7c..9e12831a704 100644
--- a/spec/models/namespace/root_storage_statistics_spec.rb
+++ b/spec/models/namespace/root_storage_statistics_spec.rb
@@ -8,6 +8,19 @@ RSpec.describe Namespace::RootStorageStatistics, type: :model do
 
   it { is_expected.to delegate_method(:all_projects).to(:namespace) }
 
+  context 'scopes' do
+    describe '.for_namespace_ids' do
+      it 'returns only requested namespaces' do
+        stats = create_list(:namespace_root_storage_statistics, 3)
+        namespace_ids = stats[0..1].map { |s| s.namespace_id }
+
+        requested_stats = described_class.for_namespace_ids(namespace_ids).pluck(:namespace_id)
+
+        expect(requested_stats).to eq(namespace_ids)
+      end
+    end
+  end
+
   describe '#recalculate!' do
     let(:namespace) { create(:group) }
     let(:root_storage_statistics) { create(:namespace_root_storage_statistics, namespace: namespace) }
diff --git a/spec/policies/namespace/root_storage_statistics_policy_spec.rb b/spec/policies/namespace/root_storage_statistics_policy_spec.rb
new file mode 100644
index 00000000000..8d53050fffb
--- /dev/null
+++ b/spec/policies/namespace/root_storage_statistics_policy_spec.rb
@@ -0,0 +1,80 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Namespace::RootStorageStatisticsPolicy do
+  using RSpec::Parameterized::TableSyntax
+
+  describe '#rules' do
+    let(:statistics) { create(:namespace_root_storage_statistics, namespace: namespace) }
+    let(:user) { create(:user) }
+
+    subject { Ability.allowed?(user, :read_statistics, statistics) }
+
+    shared_examples 'deny anonymous users' do
+      context 'when the users is anonymous' do
+        let(:user) { nil }
+
+        it { is_expected.to be_falsey }
+      end
+    end
+
+    context 'when the namespace is a personal namespace' do
+      let(:owner) { create(:user) }
+      let(:namespace) { owner.namespace }
+
+      include_examples 'deny anonymous users'
+
+      context 'when the user is not the owner' do
+        it { is_expected.to be_falsey }
+      end
+
+      context 'when the user is the owner' do
+        let(:user) { owner }
+
+        it { is_expected.to be_truthy }
+      end
+    end
+
+    context 'when the namespace is a group' do
+      let(:user)     { create(:user) }
+      let(:external) { create(:user, :external) }
+
+      shared_examples 'allows only owners' do |group_type|
+        let(:group) { create(:group, visibility_level: Gitlab::VisibilityLevel.level_value(group_type.to_s)) }
+        let(:namespace) { group }
+
+        include_examples 'deny anonymous users'
+
+        where(:user_type, :outcome) do
+          [
+            [:non_member, false],
+            [:guest, false],
+            [:reporter, false],
+            [:developer, false],
+            [:maintainer, false],
+            [:owner, true]
+          ]
+        end
+
+        with_them do
+          before do
+            group.add_user(user, user_type) unless user_type == :non_member
+          end
+
+          it { is_expected.to eq(outcome) }
+
+          context 'when the user is external' do
+            let(:user) { external }
+
+            it { is_expected.to eq(outcome) }
+          end
+        end
+      end
+
+      include_examples 'allows only owners', :public
+      include_examples 'allows only owners', :private
+      include_examples 'allows only owners', :internal
+    end
+  end
+end
diff --git a/spec/policies/namespace_policy_spec.rb b/spec/policies/namespace_policy_spec.rb
index 99fa8b1fe44..216aaae70ee 100644
--- a/spec/policies/namespace_policy_spec.rb
+++ b/spec/policies/namespace_policy_spec.rb
@@ -6,7 +6,7 @@ describe NamespacePolicy do
   let(:admin) { create(:admin) }
   let(:namespace) { create(:namespace, owner: owner) }
 
-  let(:owner_permissions) { [:create_projects, :admin_namespace, :read_namespace] }
+  let(:owner_permissions) { [:create_projects, :admin_namespace, :read_namespace, :read_statistics] }
 
   subject { described_class.new(current_user, namespace) }
 
diff --git a/spec/requests/api/graphql/namespace/root_storage_statistics_spec.rb b/spec/requests/api/graphql/namespace/root_storage_statistics_spec.rb
new file mode 100644
index 00000000000..ac76d991bd4
--- /dev/null
+++ b/spec/requests/api/graphql/namespace/root_storage_statistics_spec.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'rendering namespace statistics' do
+  include GraphqlHelpers
+
+  let(:namespace) { user.namespace }
+  let!(:statistics) { create(:namespace_root_storage_statistics, namespace: namespace, packages_size: 5.megabytes) }
+  let(:user) { create(:user) }
+
+  let(:query) do
+    graphql_query_for('namespace',
+                      { 'fullPath' => namespace.full_path },
+                      "rootStorageStatistics { #{all_graphql_fields_for('RootStorageStatistics')} }")
+  end
+
+  shared_examples 'a working namespace with storage statistics query' do
+    it_behaves_like 'a working graphql query' do
+      before do
+        post_graphql(query, current_user: user)
+      end
+    end
+
+    it 'includes the packages size if the user can read the statistics' do
+      post_graphql(query, current_user: user)
+
+      expect(graphql_data['namespace']['rootStorageStatistics']).not_to be_blank
+      expect(graphql_data['namespace']['rootStorageStatistics']['packagesSize']).to eq(5.megabytes)
+    end
+  end
+
+  it_behaves_like 'a working namespace with storage statistics query'
+
+  context 'when the namespace is a group' do
+    let(:group) { create(:group) }
+    let(:namespace) { group }
+
+    before do
+      group.add_owner(user)
+    end
+
+    it_behaves_like 'a working namespace with storage statistics query'
+
+    context 'when the namespace is public' do
+      let(:group) { create(:group, :public)}
+
+      it 'hides statistics for unauthenticated requests' do
+        post_graphql(query, current_user: nil)
+
+        expect(graphql_data['namespace']).to be_blank
+      end
+    end
+  end
+end
diff --git a/spec/requests/api/graphql/project/project_statistics_spec.rb b/spec/requests/api/graphql/project/project_statistics_spec.rb
index 14a3f37b779..ddee8537454 100644
--- a/spec/requests/api/graphql/project/project_statistics_spec.rb
+++ b/spec/requests/api/graphql/project/project_statistics_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe 'rendering namespace statistics' do
+describe 'rendering project statistics' do
   include GraphqlHelpers
 
   let(:project) { create(:project) }
diff --git a/spec/support/shared_contexts/policies/group_policy_shared_context.rb b/spec/support/shared_contexts/policies/group_policy_shared_context.rb
index fd24c443288..b89723b1e1a 100644
--- a/spec/support/shared_contexts/policies/group_policy_shared_context.rb
+++ b/spec/support/shared_contexts/policies/group_policy_shared_context.rb
@@ -31,7 +31,8 @@ RSpec.shared_context 'GroupPolicy context' do
       :admin_group_member,
       :change_visibility_level,
       :set_note_created_at,
-      :create_subgroup
+      :create_subgroup,
+      :read_statistics
     ].compact
   end