create subgroup without create project permission

app/views/groups/_home_panel.html.haml

 - can_create_subgroups = can?(current_user, :create_subgroup, @group)
+- can_create_projects = can?(current_user, :create_projects, @group)
 - emails_disabled = @group.emails_disabled?
 
 .group-home-panel
@@ -23,10 +24,9 @@
       - if current_user
         .group-buttons
           = render 'shared/notifications/new_button', notification_setting: @notification_setting, btn_class: 'btn', emails_disabled: emails_disabled
-          - if can? current_user, :create_projects, @group
           - new_project_label = _("New project")
           - new_subgroup_label = _("New subgroup")
-            - if can_create_subgroups
+          - if can_create_projects and can_create_subgroups
             .btn-group.new-project-subgroup.droplab-dropdown.home-panel-action-button.prepend-top-default.js-new-project-subgroup.qa-new-project-or-subgroup-dropdown{ data: { project_path: new_project_path(namespace_id: @group.id), subgroup_path: new_group_path(parent_id: @group.id) } }
               %input.btn.btn-success.dropdown-primary.js-new-group-child.qa-new-in-group-button{ type: "button", value: new_project_label, data: { action: "new-project" } }
               %button.btn.btn-success.dropdown-toggle.js-dropdown-toggle.qa-new-project-or-subgroup-dropdown-toggle{ type: "button", data: { "dropdown-trigger" => "#new-project-or-subgroup-dropdown", 'display' => 'static' } }
@@ -47,8 +47,10 @@
                       .description
                         %strong= new_subgroup_label
                         %span= s_("GroupsTree|Create a subgroup in this group.")
-            - else
+          - elsif can_create_projects
             = link_to new_project_label, new_project_path(namespace_id: @group.id), class: "btn btn-success prepend-top-default"
+          - elsif can_create_subgroups
+            = link_to new_subgroup_label, new_group_path(parent_id: @group.id), class: "btn btn-success prepend-top-default"
 
   - if @group.description.present?
     .group-home-desc.mt-1

changelogs/unreleased/205513-create-subgroup-without-project-permission.yml

+---
+title: Always display new subgroup button when permission is granted
+merge_request: 28309
+author: Mattias Michaux
+type: fixed

spec/features/groups_spec.rb

@@ -262,6 +262,42 @@ describe 'Group' do
     end
   end
 
+  describe 'new subgroup / project button' do
+    let(:group) { create(:group, project_creation_level: Gitlab::Access::NO_ONE_PROJECT_ACCESS, subgroup_creation_level: Gitlab::Access::OWNER_SUBGROUP_ACCESS) }
+
+    it 'new subgroup button is displayed without project creation permission' do
+      visit group_path(group)
+
+      page.within '.group-buttons' do
+        expect(page).to have_link('New subgroup')
+      end
+    end
+
+    it 'new subgroup button is displayed together with new project button when having project creation permission' do
+      group.update!(project_creation_level: Gitlab::Access::MAINTAINER_PROJECT_ACCESS)
+      visit group_path(group)
+
+      page.within '.group-buttons' do
+        expect(page).to have_css("li[data-text='New subgroup']", visible: false)
+        expect(page).to have_css("li[data-text='New project']", visible: false)
+      end
+    end
+
+    it 'new project button is displayed without subgroup creation permission' do
+      group.update!(project_creation_level: Gitlab::Access::MAINTAINER_PROJECT_ACCESS)
+      user = create(:user)
+
+      group.add_maintainer(user)
+      sign_out(:user)
+      sign_in(user)
+
+      visit group_path(group)
+      page.within '.group-buttons' do
+        expect(page).to have_link('New project')
+      end
+    end
+  end
+
   def remove_with_confirm(button_text, confirm_with)
     click_button button_text
     fill_in 'confirm_name_input', with: confirm_with