Hide nested group UI/API support for MySQL

This hides/disables some UI elements and API parameters related to
nested groups when MySQL is used, since nested groups are not supported
for MySQL.

app/controllers/groups_controller.rb

@@ -64,6 +64,8 @@ class GroupsController < Groups::ApplicationController
   end
   def subgroups
+    return not_found unless Group.supports_nested_groups?
+
     @nested_groups = GroupsFinder.new(current_user, parent: group).execute
     @nested_groups = @nested_groups.search(params[:filter_groups]) if params[:filter_groups].present?
   end

app/models/namespace.rb

@@ -178,7 +178,7 @@ class Namespace < ActiveRecord::Base
   # Returns all the ancestors of the current namespaces.
   def ancestors
-    return self.class.none if !Group.supports_nested_groups? || !parent_id
+    return self.class.none unless parent_id
     Gitlab::GroupHierarchy.
       new(self.class.where(id: parent_id)).
@@ -187,8 +187,6 @@ class Namespace < ActiveRecord::Base
   # Returns all the descendants of the current namespace.
   def descendants
-    return self.class.none unless Group.supports_nested_groups?
-
     Gitlab::GroupHierarchy.
       new(self.class.where(parent_id: id)).
       base_and_descendants

app/models/user.rb

@@ -509,8 +509,6 @@ class User < ActiveRecord::Base
   # Returns a relation of groups the user has access to, including their parent
   # and child groups (recursively).
   def all_expanded_groups
-    return groups unless Group.supports_nested_groups?
-
     Gitlab::GroupHierarchy.new(groups).all_groups
   end

app/views/groups/_show_nav.html.haml

@@ -2,6 +2,7 @@
   = nav_link(page: group_path(@group)) do
     = link_to group_path(@group) do
       Projects
-  = nav_link(page: subgroups_group_path(@group)) do
-    = link_to subgroups_group_path(@group) do
-      Subgroups
+  - if Group.supports_nested_groups?
+    = nav_link(page: subgroups_group_path(@group)) do
+      = link_to subgroups_group_path(@group) do
+        Subgroups

lib/api/entities.rb

@@ -152,7 +152,10 @@ module API
       expose :web_url
       expose :request_access_enabled
       expose :full_name, :full_path
-      expose :parent_id
+
+      if ::Group.supports_nested_groups?
+        expose :parent_id
+      end
       expose :statistics, if: :statistics do
         with_options format_with: -> (value) { value.to_i } do

lib/api/groups.rb

@@ -70,7 +70,11 @@ module API
       params do
         requires :name, type: String, desc: 'The name of the group'
         requires :path, type: String, desc: 'The path of the group'
-        optional :parent_id, type: Integer, desc: 'The parent group id for creating nested group'
+
+        if ::Group.supports_nested_groups?
+          optional :parent_id, type: Integer, desc: 'The parent group id for creating nested group'
+        end
+
         use :optional_params
       end
       post do

lib/api/v3/entities.rb

@@ -137,7 +137,10 @@ module API
         expose :web_url
         expose :request_access_enabled
         expose :full_name, :full_path
-        expose :parent_id
+
+        if ::Group.supports_nested_groups?
+          expose :parent_id
+        end
         expose :statistics, if: :statistics do
           with_options format_with: -> (value) { value.to_i } do

lib/api/v3/groups.rb

@@ -74,7 +74,11 @@ module API
         params do
           requires :name, type: String, desc: 'The name of the group'
           requires :path, type: String, desc: 'The path of the group'
-          optional :parent_id, type: Integer, desc: 'The parent group id for creating nested group'
+
+          if ::Group.supports_nested_groups?
+            optional :parent_id, type: Integer, desc: 'The parent group id for creating nested group'
+          end
+
           use :optional_params
         end
         post do

lib/gitlab/group_hierarchy.rb

@@ -15,12 +15,16 @@ module Gitlab
     # Returns a relation that includes the base set of groups and all their
     # ancestors (recursively).
     def base_and_ancestors
+      return model.none unless Group.supports_nested_groups?
+
       base_and_ancestors_cte.apply_to(model.all)
     end
     # Returns a relation that includes the base set of groups and all their
     # descendants (recursively).
     def base_and_descendants
+      return model.none unless Group.supports_nested_groups?
+
       base_and_descendants_cte.apply_to(model.all)
     end
@@ -45,6 +49,8 @@ module Gitlab
     # Using this approach allows us to further add criteria to the relation with
     # Rails thinking it's selecting data the usual way.
     def all_groups
+      return base unless Group.supports_nested_groups?
+
       ancestors = base_and_ancestors_cte
       descendants = base_and_descendants_cte

lib/gitlab/project_authorizations/with_nested_groups.rb

@@ -19,9 +19,6 @@ module Gitlab
         projects = Project.arel_table
         links = ProjectGroupLink.arel_table
-        # These queries don't directly use the user object so they don't depend
-        # on the state of said object, ensuring the produced queries are always
-        # the same.
         relations = [
           # The project a user has direct access to.
           user.projects.select_for_project_authorization,

spec/controllers/groups_controller_spec.rb

@@ -26,7 +26,7 @@ describe GroupsController do
     end
   end
-  describe 'GET #subgroups' do
+  describe 'GET #subgroups', :nested_groups do
     let!(:public_subgroup) { create(:group, :public, parent: group) }
     let!(:private_subgroup) { create(:group, :private, parent: group) }

spec/spec_helper.rb

@@ -95,7 +95,7 @@ RSpec.configure do |config|
   end
   config.around(:each, :nested_groups) do |example|
-    example.run if Gitlab::GroupHierarchy.supports_nested_groups?
+    example.run if Group.supports_nested_groups?
   end
   config.around(:each, :postgresql) do |example|