Add new slot for showing customized loading indicator

Author: bsatarnejad

app/components/primer/open_project/filterable_tree_view.html.erb

@@ -27,12 +27,16 @@
           <% tree.with_leaf(**@no_results_node_arguments) %>
         <% end %>
       <% end %>
-      <div class="FilterableTreeViewLoadingSkeleton" aria-hidden="true">
-        <% [0, 8, 8, 16, 8, 0, 8, 8].each do |indent| %>
-          <span class="TreeViewSkeletonItemContainerStyle" style="padding-left: <%= indent %>px">
-            <%= render(Primer::Alpha::SkeletonBox.new(width: "16px")) %>
-            <%= render(Primer::Alpha::SkeletonBox.new(classes: "TreeItemSkeletonTextStyles")) %>
-          </span>
+      <div class="FilterableTreeViewLoadingIndicator FilterableTreeViewLoadingSkeleton" aria-hidden="true">
+        <% if loading_indicator? %>
+          <%= loading_indicator %>
+        <% else %>
+          <% [0, 8, 8, 16, 8, 0, 8, 8].each do |indent| %>
+            <span class="TreeViewSkeletonItemContainerStyle" style="padding-left: <%= indent %>px">
+              <%= render(Primer::Alpha::SkeletonBox.new(width: "16px")) %>
+              <%= render(Primer::Alpha::SkeletonBox.new(classes: "TreeItemSkeletonTextStyles")) %>
+            </span>
+          <% end %>
         <% end %>
       </div>
       <%= render(@tree_view) %>

app/components/primer/open_project/filterable_tree_view.rb

@@ -133,11 +133,19 @@ module OpenProject
     # ```erb
     # <%= render(Primer::OpenProject::FilterableTreeView.new(
     #   src: my_path
-    # )) %>
+    # )) do |tree_view| %>
+    #   <% tree_view.with_loading_indicator do %>
+    #     <%= render(Primer::Beta::Spinner.new) %>
+    #   <% end %>
+    # <% end %>
     # ```
     class FilterableTreeView < Primer::Component
       delegate :with_leaf, :with_sub_tree, to: :@tree_view
 
+      # An optional loading indicator shown while an async filter request is in progress. When omitted, a skeleton
+      # loader is rendered. This slot is only used when `src` is set.
+      renders_one :loading_indicator
+
       SUPPORTED_SELECT_VARIANTS = %i[multiple single none].freeze
 
       DEFAULT_FILTER_INPUT_ARGUMENTS = {