Delegate config to parent modules (no-op) (#2231)

* Delegate config to parent modules

Adds a mechanism for inheriting config from a parent module. There's definitely more that needs to be done to iron this out, including:
- if the module does not already respond to `config`, provide a concern that sets it up using `ActiveSupport::Configurable`
- if the module _does_ already respond to `config` and doesn't have `view_component` set on it, set it up.
- if the module's config does have `view_component` set up, leave it alone?

I also need to consider whether the current way of having things refer back to the Rails app config is appropriate.

Since `Base` is generally used when referring to "global" config options, this probably doesn't do anything right now, but settings like
`test_controller` and `generate` should opt into it.

* Provide ViewComponent::Configurable module

This can be included on a module to provide module-local configuration for ViewComponent. It avoids overwriting existing configuration that may already exist.

* Adjust allocations

* Update changelog

Author: boardfish

docs/CHANGELOG.md

@@ -10,6 +10,10 @@ nav_order: 5
 
 ## main
 
+* Add unused mechanism for inheriting config from parent modules to enable future engine-local configuration.
+
+    *Simon Fish*
+
 * Improve handling of malformed component edge case when mocking components in tests.
 
     *Martin Meyerhoff*, *Joel Hawksley*

lib/view_component/base.rb

@@ -25,6 +25,10 @@ class << self
       #
       # @return [ActiveSupport::OrderedOptions]
       def config
+        module_parents.each do |m|
+          config = m.try(:config).try(:view_component)
+          return config if config
+        end
         ViewComponent::Config.current
       end
     end

lib/view_component/configurable.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module ViewComponent
+  module Configurable
+    extend ActiveSupport::Concern
+
+    included do
+      next if respond_to?(:config) && config.respond_to?(:view_component) && config.respond_to_missing?(:test_controller)
+
+      include ActiveSupport::Configurable
+
+      configure do |config|
+        config.view_component ||= ActiveSupport::InheritableOptions.new
+      end
+    end
+  end
+end

test/sandbox/test/base_test.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "test_helper"
+require "view_component/configurable"
 
 class ViewComponent::Base::UnitTest < Minitest::Test
   def test_identifier
@@ -146,4 +147,54 @@ def test_no_method_error_does_not_reference_missing_helper
     MESSAGE
     assert !exception_message_regex.match?(exception.message)
   end
+
+  module TestModuleWithoutConfig
+    class SomeComponent < ViewComponent::Base
+    end
+  end
+
+  # Config defined on top-level module as opposed to engine.
+  module TestModuleWithConfig
+    include ViewComponent::Configurable
+
+    configure do |config|
+      config.view_component.test_controller = "AnotherController"
+    end
+
+    class SomeComponent < ViewComponent::Base
+    end
+  end
+
+  module TestAlreadyConfigurableModule
+    include ActiveSupport::Configurable
+    include ViewComponent::Configurable
+
+    configure do |config|
+      config.view_component.test_controller = "AnotherController"
+    end
+
+    class SomeComponent < ViewComponent::Base
+    end
+  end
+
+  module TestAlreadyConfiguredModule
+    include ActiveSupport::Configurable
+
+    configure do |config|
+      config.view_component = ActiveSupport::InheritableOptions[test_controller: "AnotherController"]
+    end
+
+    include ViewComponent::Configurable
+
+    class SomeComponent < ViewComponent::Base
+    end
+  end
+
+  def test_uses_module_configuration
+    # We override this ourselves in test/sandbox/config/environments/test.rb.
+    assert_equal "IntegrationExamplesController", TestModuleWithoutConfig::SomeComponent.test_controller
+    assert_equal "AnotherController", TestModuleWithConfig::SomeComponent.test_controller
+    assert_equal "AnotherController", TestAlreadyConfigurableModule::SomeComponent.test_controller
+    assert_equal "AnotherController", TestAlreadyConfiguredModule::SomeComponent.test_controller
+  end
 end

test/sandbox/test/rendering_test.rb

@@ -16,8 +16,8 @@ def test_render_inline_allocations
     MyComponent.ensure_compiled
 
     allocations = (Rails.version.to_f >= 8.0) ?
-      {"3.5.0" => 115, "3.4.2" => 117, "3.3.7" => 129} :
-      {"3.3.7" => 120, "3.3.0" => 132, "3.2.7" => 118, "3.1.6" => 118, "3.0.7" => 127}
+      {"3.5.0" => 123, "3.4.2" => 125, "3.3.7" => 137} :
+      {"3.3.7" => 128, "3.3.0" => 140, "3.2.7" => 126, "3.1.6" => 126, "3.0.7" => 135}
 
     assert_allocations(**allocations) do
       render_inline(MyComponent.new)