1 files changed, 58 insertions, 5 deletions
diff --git a/app/models/preloaders/user_max_access_level_in_groups_preloader.rb b/app/models/preloaders/user_max_access_level_in_groups_preloader.rb
index 8df986b47a2..0c747ad9c84 100644
--- a/app/models/preloaders/user_max_access_level_in_groups_preloader.rb
+++ b/app/models/preloaders/user_max_access_level_in_groups_preloader.rb
@@ -32,11 +32,12 @@ module Preloaders
     end
 
     def preload_with_traversal_ids
-      max_access_levels = GroupMember.active_without_invites_and_requests
-                                     .where(user: @user)
-                                     .joins("INNER JOIN (#{traversal_join_sql}) as hierarchy ON members.source_id = hierarchy.traversal_id")
-                                     .group('hierarchy.id')
-                                     .maximum(:access_level)
+      # Diagrammatic representation of this step:
+      # https://gitlab.com/gitlab-org/gitlab/-/merge_requests/111157#note_1271550140
+      max_access_levels = GroupMember.from_union(all_memberships)
+                            .joins("INNER JOIN (#{traversal_join_sql}) as hierarchy ON members.source_id = hierarchy.traversal_id")
+                            .group('hierarchy.id')
+                            .maximum(:access_level)
 
       @groups.each do |group|
         max_access_level = max_access_levels[group.id] || Gitlab::Access::NO_ACCESS
@@ -44,6 +45,58 @@ module Preloaders
       end
     end
 
+    def all_memberships
+      if Feature.enabled?(:include_memberships_from_group_shares_in_preloader)
+        [
+          direct_memberships.select(*GroupMember.cached_column_list),
+          memberships_from_group_shares
+        ]
+      else
+        [direct_memberships]
+      end
+    end
+
+    def direct_memberships
+      GroupMember.active_without_invites_and_requests.where(user: @user)
+    end
+
+    def memberships_from_group_shares
+      alter_direct_memberships_to_make_it_act_like_memberships_in_shared_groups
+    end
+
+    def alter_direct_memberships_to_make_it_act_like_memberships_in_shared_groups
+      group_group_link_table = GroupGroupLink.arel_table
+      group_member_table = GroupMember.arel_table
+
+      altered_columns = GroupMember.attribute_names.map do |column_name|
+        case column_name
+        when 'access_level'
+          # Consider the limiting effect of group share's access level
+          smallest_value_arel([group_group_link_table[:group_access], group_member_table[:access_level]], 'access_level')
+        when 'source_id'
+          # Alter the `source_id` of the `Member` record that is currently pointing to the `shared_with_group`
+          # such that this record would now behave like a `Member` record of this user pointing to the `shared_group` group.
+          Arel::Nodes::As.new(group_group_link_table[:shared_group_id], Arel::Nodes::SqlLiteral.new('source_id'))
+        else
+          group_member_table[column_name]
+        end
+      end
+
+      direct_memberships_in_groups_that_have_been_shared_with_other_groups.select(*altered_columns)
+    end
+
+    def direct_memberships_in_groups_that_have_been_shared_with_other_groups
+      direct_memberships.joins(
+        "INNER JOIN group_group_links ON members.source_id = group_group_links.shared_with_group_id"
+      )
+    end
+
+    def smallest_value_arel(args, column_alias)
+      Arel::Nodes::As.new(
+        Arel::Nodes::NamedFunction.new('LEAST', args),
+        Arel::Nodes::SqlLiteral.new(column_alias))
+    end
+
     def traversal_join_sql
       Namespace.select('id, unnest(traversal_ids) as traversal_id').where(id: @groups.map(&:id)).to_sql
     end