Deprecate BorderBox list_id param

Adds a deprecation warning for the `list_id:` param, now superseded by
the more general `list_arguments: { id: ... }` introduced in this branch.
The deprecated param no longer overrides an id supplied via
`list_arguments`.

Author: myabc

app/components/primer/beta/border_box.rb

@@ -72,9 +72,11 @@ class BorderBox < Primer::Component
 
       # @param padding [Symbol] <%= one_of(Primer::Beta::BorderBox::PADDING_MAPPINGS.keys) %>
       # @param list_arguments [Hash] <%= link_to_system_arguments_docs %>
+      # @param list_id [String] Deprecated. Use <code>list_arguments: { id: ... }</code> instead.
       # @param system_arguments [Hash] <%= link_to_system_arguments_docs %>
       def initialize(padding: DEFAULT_PADDING, list_arguments: {}, **system_arguments)
         list_id = system_arguments.delete(:list_id)
+        deprecation_warn("The `list_id:` param is deprecated. Use `list_arguments: { id: ... }` instead. It will be removed in a future version.") if list_id
 
         @system_arguments = deny_tag_argument(**system_arguments)
         @system_arguments[:tag] = :div
@@ -87,7 +89,7 @@ def initialize(padding: DEFAULT_PADDING, list_arguments: {}, **system_arguments)
         @system_arguments[:system_arguments_denylist] = { [:p, :pt, :pb, :pr, :pl] => PADDING_SUGGESTION }
         @list_arguments = deny_tag_argument(**list_arguments)
         @list_arguments[:tag] = :ul
-        @list_arguments[:id] = list_id if list_id
+        @list_arguments[:id] ||= list_id if list_id
         @list_arguments[:classes] = class_names("Box-list", @list_arguments[:classes])
       end
 
@@ -105,6 +107,12 @@ def before_render
           { aria: { labelledby: header.id } }
         )
       end
+
+      def deprecation_warn(message)
+        return if Rails.env.production? || silence_deprecations?
+
+        ::Primer::ViewComponents.deprecation.warn(message)
+      end
     end
   end
 end

test/components/beta/border_box_test.rb

@@ -91,6 +91,24 @@ def test_renders_the_list_element_with_an_id_if_provided
     assert_selector("li.Box-row", count: 1)
   end
 
+  def test_warns_when_list_id_param_passed
+    with_silence_deprecations(false) do
+      ::Primer::ViewComponents.deprecation.expects(:warn).with("The `list_id:` param is deprecated. Use `list_arguments: { id: ... }` instead. It will be removed in a future version.").once
+      render_inline(Primer::Beta::BorderBox.new(list_id: "an-id")) do |component|
+        component.with_row { "First" }
+      end
+    end
+  end
+
+  def test_list_arguments_id_takes_precedence_over_deprecated_list_id
+    render_inline(Primer::Beta::BorderBox.new(list_id: "old-id", list_arguments: { id: "new-id" })) do |component|
+      component.with_row { "First" }
+    end
+
+    assert_selector("ul#new-id", count: 1)
+    assert_no_selector("ul#old-id")
+  end
+
   def test_renders_condensed
     render_inline(Primer::Beta::BorderBox.new(padding: :condensed)) do |component|
       component.with_body { "Body" }