Introduce SystemArguments; only focus on SelectPanel for now

app/components/primer/alpha/select_panel.rb

@@ -362,7 +362,7 @@ def with_avatar_item(**system_arguments)
 
       alias show_filter? show_filter
 
-      # @param src [String, nil] The URL to fetch search results from.
+      # @param src [String, NilClass] The URL to fetch search results from.
       # @param title [String] The title that appears at the top of the panel.
       # @param id [String] The unique ID of the panel.
       # @param size [Symbol] The size of the panel. <%= one_of(Primer::Alpha::Overlay::SIZE_OPTIONS) %>
@@ -371,19 +371,19 @@ def with_avatar_item(**system_arguments)
       # @param no_results_label [String] The label to display when no results are found.
       # @param preload [Boolean] Whether to preload search results when the page loads. If this option is false, results are loaded when the panel is opened.
       # @param dynamic_label [Boolean] Whether or not to display the text of the currently selected item in the show button.
-      # @param dynamic_label_prefix [String, nil] If provided, the prefix is prepended to the dynamic label and displayed in the show button.
-      # @param dynamic_aria_label_prefix [String, nil] If provided, the prefix is prepended to the dynamic label and set as the value of the `aria-label` attribute on the show button.
-      # @param body_id [String, nil] The unique ID of the panel body. If not provided, the body ID will be set to the panel ID with a "-body" suffix.
-      # @param list_arguments [Hash] Arguments to pass to the underlying <%= link_to_component(Primer::Alpha::ActionList) %> component. Only has an effect for the local fetch strategy.
-      # @param form_arguments [Hash] Form arguments to pass to the underlying <%= link_to_component(Primer::Alpha::ActionList) %> component. Only has an effect for the local fetch strategy.
+      # @param dynamic_label_prefix [String, NilClass] If provided, the prefix is prepended to the dynamic label and displayed in the show button.
+      # @param dynamic_aria_label_prefix [String, NilClass] If provided, the prefix is prepended to the dynamic label and set as the value of the `aria-label` attribute on the show button.
+      # @param body_id [String, NilClass] The unique ID of the panel body. If not provided, the body ID will be set to the panel ID with a "-body" suffix.
+      # @param list_arguments [SystemArguments] Arguments to pass to the underlying <%= link_to_component(Primer::Alpha::ActionList) %> component. Only has an effect for the local fetch strategy.
+      # @param form_arguments [SystemArguments] Form arguments to pass to the underlying <%= link_to_component(Primer::Alpha::ActionList) %> component. Only has an effect for the local fetch strategy.
       # @param show_filter [Boolean] Whether or not to show the filter input.
       # @param open_on_load [Boolean] Open the panel when the page loads.
       # @param anchor_align [Symbol] The anchor alignment of the Overlay. <%= one_of(Primer::Alpha::Overlay::ANCHOR_ALIGN_OPTIONS) %>
       # @param anchor_side [Symbol] The side to anchor the Overlay to. <%= one_of(Primer::Alpha::Overlay::ANCHOR_SIDE_OPTIONS) %>
       # @param loading_label [String] The aria-label to use when the panel is loading, defaults to 'Loading content...'.
-      # @param loading_description [String, nil] The description to use when the panel is loading. If not provided, no description will be used.
+      # @param loading_description [String, NilClass] The description to use when the panel is loading. If not provided, no description will be used.
       # @param banner_scheme [Symbol] The scheme for the error banner <%= one_of(Primer::Alpha::SelectPanel::BANNER_SCHEME_OPTIONS) %>
-      # @param system_arguments [Hash] <%= link_to_system_arguments_docs %>
+      # @param system_arguments [SystemArguments] <%= link_to_system_arguments_docs %>
       def initialize(
         src: nil,
         title: "Menu",

app/components/primer/component.rb

@@ -2,13 +2,8 @@
 
 require "view_component/version"
 
+# :nodoc:
 module Primer
-  extend T::Sig
-
-  SystemArguments = T.type_alias do
-    Hash[T.any(Symbol, String), T.any(String, Numeric)]
-  end
-
   # @private
   # :nocov:
   class Component < ViewComponent::Base

demo/sorbet/rbi/custom/system_arguments.rbi

@@ -0,0 +1,28 @@
+SystemArguments = T.type_alias do
+  T::Hash[
+    # key
+    T.any(Symbol, String),
+
+    # value
+    T.any(
+      Symbol,
+      String,
+      Numeric,
+
+      # aria: { ... } and data: { ... }
+      T::Hash[
+        # key (:aria, "aria", :data, or "data")
+        T.any(Symbol, String),
+
+        # value (possibly a nested hash)
+        T.any(Symbol, String, T::Hash[
+          # key inside aria or data hash
+          T.any(Symbol, String),
+
+          # value
+          T.any(Symbol, String, Numeric)
+        ])
+      ]
+    )
+  ]
+end