Centralize ViewComponent::Base config (#1291)

* Update changelog

* Clean up mirrored config options from ViewComponent::Base

* Refactor generate test helper

* Test that app config and ViewComponent::Base config are equivalent

* Update documentation on defaults

* Update lib/view_component/base.rb

Co-authored-by: Hans Lemuet <Spone@users.noreply.github.com>

* Create dedicated config object

* Move default config to constant

* Test to ensure preview_path alias is maintained

* Use OrderedOptions for generate config option to maintain behavior

* Update some defaults

* Remove duplicate config definitions

These are specified in ViewComponent::Config now.

* Clarify necessity of specifying preview paths

* Delegate the majority of config options back to application config

* Move remainder of Previewable accessors to app config

* Extract out default preview paths

* Make all config accessors accessible on ViewComponent::Base by default

* Remove the Previewable module

ALl it did was make preview-related config accessible on ViewComponent::Base

* Add default_preview_layout to global config

* Run `bundle update`

* Make ViewComponent::Base the source of truth for config

* Add backwards compatibility for config_accessor defaults

* Restore documentation for config options

* Improve test coverage

* Directly require ViewComponent::Base to fix Primer CI

* Directly require ViewComponent::Config to fix Primer CI

* Move config require to ViewComponent::Base

* Require ViewComponent::Deprecation in Config

* Add missing defaults

* Reset default_preview_layout to `nil`

* Remove all changes to docs/api.md

* Add code ownership

* s/with_generate/with_generate_option/

* Explain alias between .default and .new

* Draft test to ensure all config options are documented

The pieces are in place, but I think the final aim is that everything
for which there's a default and/or a reader is documented

* Ensure accessors defined in public methods are considered too

* Coerce to string for backwards compatibility

* Lint

* Use Ruby 3.0.3

* Add more detailed changelog message

Co-authored-by: Joel Hawksley <joel@hawksley.org>

* Manually restore the Previewable changes after rebase

* Lint

* Remove global output buffer option

* Remove previewable module

Config options for preview are now under ViewComponent::Config.

* Make Rails.application.config.view_component the source of truth

ViewComponent::Base should continue to work but will delegate back to that.

* Update missed stub

* Update Gemfile.lock

* Compose around ActiveSupport::OrderedOptions

Co-authored-by: Hans Lemuet <Spone@users.noreply.github.com>
Co-authored-by: Joel Hawksley <joel@hawksley.org>

.github/CODEOWNERS

@@ -26,7 +26,6 @@
 /app/**/* @juanmanuelramallo
 /docs/guide/previews.md @juanmanuelramallo
 /lib/view_component/preview.rb @juanmanuelramallo
-/lib/view_component/previewable.rb @juanmanuelramallo
 /lib/view_component/preview_template_error.rb @juanmanuelramallo
 /test/sandbox/test/components/previews/preview_source_from_layout_component_preview.rb @juanmanuelramallo
 /test/view_component/default_preview_layout_integration_test.rb @juanmanuelramallo
@@ -46,3 +45,5 @@
 /script/replicate-bug @boardfish
 /lib/view_component/docs_builder_component.rb @boardfish
 /lib/view_component/docs_builder_component.html.erb @boardfish
+/lib/view_component/config.rb @boardfish
+/test/view_component/config_test.rb @boardfish

Rakefile

@@ -70,9 +70,7 @@ namespace :docs do
 
     instance_methods_to_document = meths.select { |method| method.scope != :class }
     class_methods_to_document = meths.select { |method| method.scope == :class }
-    configuration_methods_to_document = registry.get("ViewComponent::Base").meths.select { |method|
-      method[:mattr_accessor]
-    }
+    configuration_methods_to_document = registry.get("ViewComponent::Config").meths.select(&:reader?)
     test_helper_methods_to_document = registry
       .get("ViewComponent::TestHelpers")
       .meths

app/controllers/concerns/view_component/preview_actions.rb

@@ -10,9 +10,7 @@ module ViewComponent
       around_action :set_locale, only: :previews
       before_action :require_local!, unless: :show_previews?
 
-      if respond_to?(:content_security_policy)
-        content_security_policy(false)
-      end
+      content_security_policy(false) if respond_to?(:content_security_policy)
     end
 
     def index
@@ -45,18 +43,18 @@ module ViewComponent
 
     # :doc:
     def default_preview_layout
-      ViewComponent::Base.default_preview_layout
+      Rails.application.config.view_component.default_preview_layout
     end
 
     # :doc:
     def show_previews?
-      ViewComponent::Base.show_previews
+      Rails.application.config.view_component.show_previews
     end
 
     # :doc:
     def find_preview
       candidates = []
-      params[:path].to_s.scan(%r{/|$}) { candidates << $` }
+      params[:path].to_s.scan(%r{/|$}) { candidates << Regexp.last_match.pre_match }
       preview = candidates.detect { |candidate| ViewComponent::Preview.exists?(candidate) }
 
       if preview
@@ -66,10 +64,8 @@ module ViewComponent
       end
     end
 
-    def set_locale
-      I18n.with_locale(params[:locale] || I18n.default_locale) do
-        yield
-      end
+    def set_locale(&block)
+      I18n.with_locale(params[:locale] || I18n.default_locale, &block)
     end
 
     # Returns either {} or {layout: value} depending on configuration

app/helpers/preview_helper.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module PreviewHelper
-  AVAILABLE_PRISM_LANGUAGES = ["ruby", "erb", "haml"]
+  AVAILABLE_PRISM_LANGUAGES = %w[ruby erb haml]
   FALLBACK_LANGUAGE = "ruby"
 
   def preview_source
@@ -22,7 +22,7 @@ module PreviewHelper
       # Fetch template source via finding it through preview paths
       # to accomodate source view when exclusively using templates
       # for previews for Rails < 6.1.
-      all_template_paths = ViewComponent::Base.preview_paths.map do |preview_path|
+      all_template_paths = Rails.application.config.view_component.preview_paths.map do |preview_path|
         Dir.glob("#{preview_path}/**/*")
       end.flatten
 

app/views/view_components/preview.html.erb

@@ -1,5 +1,5 @@
 <% if @render_args[:component] %>
-  <% if ViewComponent::Base.render_monkey_patch_enabled || Rails.version.to_f >= 6.1 %>
+  <% if Rails.application.config.view_component.render_monkey_patch_enabled || Rails.version.to_f >= 6.1 %>
     <%= render(@render_args[:component], @render_args[:args], &@render_args[:block]) %>
   <% else %>
     <%= render_component(@render_args[:component], &@render_args[:block]) %>
@@ -8,6 +8,6 @@
   <%= render template: @render_args[:template], locals: @render_args[:locals] || {} %>
 <% end %>
 
-<% if ViewComponent::Base.show_previews_source %>
+<% if Rails.application.config.view_component.show_previews_source %>
   <%= preview_source %>
 <% end %>

docs/CHANGELOG.md

@@ -9,6 +9,10 @@ title: Changelog
 
 ## main
 
+* Add missing `generate.sidecar`, `generate.stimulus_controller`, `generate.locale`, `generate.distinct_locale_files`, `generate.preview` config options to `config.view_component`.
+
+    *Simon Fish*
+
 ## 2.65.0
 
 * Raise `ArgumentError` when conflicting Slots are defined.

lib/rails/generators/abstract_generator.rb

@@ -3,9 +3,7 @@
 module ViewComponent
   module AbstractGenerator
     def copy_view_file
-      unless options["inline"]
-        template "component.html.#{engine_name}", destination
-      end
+      template "component.html.#{engine_name}", destination unless options["inline"]
     end
 
     private
@@ -31,7 +29,7 @@ module ViewComponent
     end
 
     def component_path
-      ViewComponent::Base.view_component_path
+      Rails.application.config.view_component.view_component_path
     end
 
     def stimulus_controller
@@ -44,7 +42,7 @@ module ViewComponent
     end
 
     def sidecar?
-      options["sidecar"] || ViewComponent::Base.generate.sidecar
+      options["sidecar"] || Rails.application.config.view_component.generate.sidecar
     end
   end
 end

lib/rails/generators/component/component_generator.rb

@@ -13,11 +13,12 @@ module Rails
       check_class_collision suffix: "Component"
 
       class_option :inline, type: :boolean, default: false
-      class_option :locale, type: :boolean, default: ViewComponent::Base.generate.locale
+      class_option :locale, type: :boolean, default: Rails.application.config.view_component.generate.locale
       class_option :parent, type: :string, desc: "The parent class for the generated component"
-      class_option :preview, type: :boolean, default: ViewComponent::Base.generate.preview
+      class_option :preview, type: :boolean, default: Rails.application.config.view_component.generate.preview
       class_option :sidecar, type: :boolean, default: false
-      class_option :stimulus, type: :boolean, default: ViewComponent::Base.generate.stimulus_controller
+      class_option :stimulus, type: :boolean,
+        default: Rails.application.config.view_component.generate.stimulus_controller
 
       def create_component_file
         template "component.rb", File.join(component_path, class_path, "#{file_name}_component.rb")
@@ -40,7 +41,7 @@ module Rails
       def parent_class
         return options[:parent] if options[:parent]
 
-        ViewComponent::Base.component_parent_class || default_parent_class
+        Rails.application.config.view_component.component_parent_class || default_parent_class
       end
 
       def initialize_signature

lib/rails/generators/locale/component_generator.rb

@@ -12,7 +12,7 @@ module Locale
       class_option :sidecar, type: :boolean, default: false
 
       def create_locale_file
-        if ViewComponent::Base.generate.distinct_locale_files
+        if Rails.application.config.view_component.generate.distinct_locale_files
           I18n.available_locales.each do |locale|
             create_file destination(locale), translations_hash([locale]).to_yaml
           end

lib/view_component.rb

@@ -10,6 +10,7 @@ module ViewComponent
   autoload :Compiler
   autoload :CompileCache
   autoload :ComponentError
+  autoload :Config
   autoload :Deprecation
   autoload :Instrumentation
   autoload :Preview

lib/view_component/base.rb

@@ -4,9 +4,9 @@ require "action_view"
 require "active_support/configurable"
 require "view_component/collection"
 require "view_component/compile_cache"
+require "view_component/config"
 require "view_component/content_areas"
 require "view_component/polymorphic_slots"
-require "view_component/previewable"
 require "view_component/slotable"
 require "view_component/slotable_v2"
 require "view_component/translatable"
@@ -14,10 +14,16 @@ require "view_component/with_content_helper"
 
 module ViewComponent
   class Base < ActionView::Base
-    include ActiveSupport::Configurable
+    class << self
+      delegate(*ViewComponent::Config.defaults.keys, to: :config)
+
+      def config
+        Rails.application.config.view_component
+      end
+    end
+
     include ViewComponent::ContentAreas
     include ViewComponent::PolymorphicSlots
-    include ViewComponent::Previewable
     include ViewComponent::SlotableV2
     include ViewComponent::Translatable
     include ViewComponent::WithContentHelper
@@ -113,11 +119,9 @@ module ViewComponent
       @current_template = self
 
       if block && defined?(@__vc_content_set_by_with_content)
-        raise ArgumentError.new(
-          "It looks like a block was provided after calling `with_content` on #{self.class.name}, " \
+        raise ArgumentError, "It looks like a block was provided after calling `with_content` on #{self.class.name}, " \
           "which means that ViewComponent doesn't know which content to use.\n\n" \
           "To fix this issue, use either `with_content` or a block."
-        )
       end
 
       @__vc_content_evaluated = false
@@ -262,9 +266,7 @@ module ViewComponent
     # @private
     def format
       # Ruby 2.6 throws a warning without checking `defined?`, 2.7 doesn't
-      if defined?(@__vc_variant)
-        @__vc_variant
-      end
+      @__vc_variant if defined?(@__vc_variant)
     end
 
     # Use the provided variant instead of the one determined by the current request.
@@ -313,11 +315,9 @@ module ViewComponent
     # config.view_component.test_controller = "MyTestController"
     # ```
     #
-    # Defaults to ApplicationController. Can also be configured on a per-test
-    # basis using `with_controller_class`.
+    # Defaults to `nil`. If this is falsy, `"ApplicationController"` is used. Can also be
+    # configured on a per-test basis using `with_controller_class`.
     #
-    mattr_accessor :test_controller
-    @@test_controller = "ApplicationController"
 
     # Set if render monkey patches should be included or not in Rails <6.1:
     #
@@ -325,7 +325,6 @@ module ViewComponent
     # config.view_component.render_monkey_patch_enabled = false
     # ```
     #
-    mattr_accessor :render_monkey_patch_enabled, instance_writer: false, default: true
 
     # Path for component files
     #
@@ -333,9 +332,8 @@ module ViewComponent
     # config.view_component.view_component_path = "app/my_components"
     # ```
     #
-    # Defaults to `app/components`.
+    # Defaults to `nil`. If this is falsy, `app/components` is used.
     #
-    mattr_accessor :view_component_path, instance_writer: false, default: "app/components"
 
     # Parent class for generated components
     #
@@ -346,7 +344,6 @@ module ViewComponent
     # Defaults to nil. If this is falsy, generators will use
     # "ApplicationComponent" if defined, "ViewComponent::Base" otherwise.
     #
-    mattr_accessor :component_parent_class, instance_writer: false
 
     # Configuration for generators.
     #
@@ -397,7 +394,6 @@ module ViewComponent
     # ```
     #
     #  Defaults to `false`.
-    mattr_accessor :generate, instance_writer: false, default: ActiveSupport::OrderedOptions.new(false)
 
     class << self
       # @private
@@ -489,8 +485,8 @@ module ViewComponent
 
         # If Rails application is loaded, add application url_helpers to the component context
         # we need to check this to use this gem as a dependency
-        if defined?(Rails) && Rails.application
-          child.include Rails.application.routes.url_helpers unless child < Rails.application.routes.url_helpers
+        if defined?(Rails) && Rails.application && !(child < Rails.application.routes.url_helpers)
+          child.include Rails.application.routes.url_helpers
         end
 
         # Derive the source location of the component Ruby file from the call stack.
@@ -500,7 +496,7 @@ module ViewComponent
 
         # Removes the first part of the path and the extension.
         child.virtual_path = child.source_location.gsub(
-          %r{(.*#{Regexp.quote(ViewComponent::Base.view_component_path)})|(\.rb)}, ""
+          /(.*#{Regexp.quote(Rails.application.config.view_component.view_component_path)})|(\.rb)/, ""
         )
 
         # Set collection parameter to the extended component
@@ -591,20 +587,16 @@ module ViewComponent
         # parameters will be empty and ViewComponent will not be able to render
         # the component.
         if initialize_parameters.empty?
-          raise ArgumentError.new(
-            "The #{self} initializer is empty or invalid." \
+          raise ArgumentError, "The #{self} initializer is empty or invalid." \
             "It must accept the parameter `#{parameter}` to render it as a collection.\n\n" \
             "To fix this issue, update the initializer to accept `#{parameter}`.\n\n" \
             "See https://viewcomponent.org/guide/collections.html for more information on rendering collections."
-          )
         end
 
-        raise ArgumentError.new(
-          "The initializer for #{self} doesn't accept the parameter `#{parameter}`, " \
+        raise ArgumentError, "The initializer for #{self} doesn't accept the parameter `#{parameter}`, " \
           "which is required in order to render it as a collection.\n\n" \
           "To fix this issue, update the initializer to accept `#{parameter}`.\n\n" \
           "See https://viewcomponent.org/guide/collections.html for more information on rendering collections."
-        )
       end
 
       # Ensure the component initializer doesn't define
@@ -614,10 +606,8 @@ module ViewComponent
       def validate_initialization_parameters!
         return unless initialize_parameter_names.include?(RESERVED_PARAMETER)
 
-        raise ViewComponent::ComponentError.new(
-          "#{self} initializer can't accept the parameter `#{RESERVED_PARAMETER}`, as it will override a " \
+        raise ViewComponent::ComponentError, "#{self} initializer can't accept the parameter `#{RESERVED_PARAMETER}`, as it will override a " \
           "public ViewComponent method. To fix this issue, rename the parameter."
-        )
       end
 
       # @private

lib/view_component/config.rb

@@ -0,0 +1,159 @@
+# frozen_string_literal: true
+
+require "view_component/deprecation"
+
+module ViewComponent
+  class Config
+    class << self
+      # `new` without any arguments initializes the default configuration, but
+      # it's important to differentiate in case that's no longer the case in
+      # future.
+      alias_method :default, :new
+
+      def defaults
+        ActiveSupport::OrderedOptions.new.merge!({
+          generate: ActiveSupport::OrderedOptions.new(false),
+          preview_controller: "ViewComponentsController",
+          preview_route: "/rails/view_components",
+          show_previews_source: false,
+          instrumentation_enabled: false,
+          render_monkey_patch_enabled: true,
+          view_component_path: "app/components",
+          component_parent_class: nil,
+          show_previews: Rails.env.development? || Rails.env.test?,
+          preview_paths: default_preview_paths,
+          test_controller: "ApplicationController",
+          default_preview_layout: nil
+        })
+      end
+
+      # @!attribute generate
+      # @return [ActiveSupport::OrderedOptions]
+      # The subset of configuration options relating to generators.
+      #
+      # All options under this namespace default to `false` unless otherwise
+      # stated.
+      #
+      # #### #sidecar
+      #
+      # Always generate a component with a sidecar directory:
+      #
+      #     config.view_component.generate.sidecar = true
+      #
+      # #### #stimulus_controller
+      #
+      # Always generate a Stimulus controller alongside the component:
+      #
+      #     config.view_component.generate.stimulus_controller = true
+      #
+      # #### #locale
+      #
+      # Always generate translations file alongside the component:
+      #
+      #     config.view_component.generate.locale = true
+      #
+      # #### #distinct_locale_files
+      #
+      # Always generate as many translations files as available locales:
+      #
+      #     config.view_component.generate.distinct_locale_files = true
+      #
+      # One file will be generated for each configured `I18n.available_locales`,
+      # falling back to `[:en]` when no `available_locales` is defined.
+      #
+      # #### #preview
+      #
+      # Always generate a preview alongside the component:
+      #
+      #      config.view_component.generate.preview = true
+
+      # @!attribute preview_controller
+      # @return [String]
+      # The controller used for previewing components.
+      # Defaults to `ViewComponentsController`.
+
+      # @!attribute preview_route
+      # @return [String]
+      # The entry route for component previews.
+      # Defaults to `"/rails/view_components"`.
+
+      # @!attribute show_previews_source
+      # @return [Boolean]
+      # Whether to display source code previews in component previews.
+      # Defaults to `false`.
+
+      # @!attribute instrumentation_enabled
+      # @return [Boolean]
+      # Whether ActiveSupport notifications are enabled.
+      # Defaults to `false`.
+
+      # @!attribute render_monkey_patch_enabled
+      # @return [Boolean] Whether the #render method should be monkey patched.
+      # If this is disabled, use `#render_component` or
+      # `#render_component_to_string` instead.
+      # Defaults to `true`.
+
+      # @!attribute view_component_path
+      # @return [String]
+      # The path in which components, their templates, and their sidecars should
+      # be stored.
+      # Defaults to `"app/components"`.
+
+      # @!attribute component_parent_class
+      # @return [String]
+      # The parent class from which generated components will inherit.
+      # Defaults to `nil`. If this is falsy, generators will use
+      # `"ApplicationComponent"` if defined, `"ViewComponent::Base"` otherwise.
+
+      # @!attribute show_previews
+      # @return [Boolean]
+      # Whether component previews are enabled.
+      # Defaults to `true` in development and test environments.
+
+      # @!attribute preview_paths
+      # @return [Array<String>]
+      # The locations in which component previews will be looked up.
+      # Defaults to `['test/component/previews']` relative to your Rails root.
+
+      # @!attribute preview_path
+      # @deprecated Use #preview_paths instead. Will be removed in v3.0.0.
+
+      # @!attribute test_controller
+      # @return [String]
+      # The controller used for testing components.
+      # Can also be configured on a per-test basis using `#with_controller_class`.
+      # Defaults to `ApplicationController`.
+
+      # @!attribute default_preview_layout
+      # @return [String]
+      # A custom default layout used for the previews index page and individual
+      # previews.
+      # Defaults to `nil`. If this is falsy, `"component_preview"` is used.
+
+      def default_preview_paths
+        return [] unless defined?(Rails.root) && Dir.exist?("#{Rails.root}/test/components/previews")
+
+        ["#{Rails.root}/test/components/previews"]
+      end
+    end
+
+    def initialize
+      @config = self.class.defaults
+    end
+
+    def preview_path
+      preview_paths
+    end
+
+    def preview_path=(new_value)
+      ViewComponent::Deprecation.warn("`preview_path` will be removed in v3.0.0. Use `preview_paths` instead.")
+      self.preview_paths = Array.wrap(new_value)
+    end
+
+    delegate_missing_to :config
+
+    private
+
+    attr_reader :config
+  end
+end

lib/view_component/engine.rb

@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
 require "rails"
+require "view_component/base"
 
 module ViewComponent
   class Engine < Rails::Engine # :nodoc:
-    config.view_component = ActiveSupport::OrderedOptions.new
-    config.view_component.preview_paths ||= []
+    config.view_component = ViewComponent::Config.default
 
     rake_tasks do
       load "view_component/rails/tasks/view_component.rake"
@@ -14,25 +14,20 @@ module ViewComponent
     initializer "view_component.set_configs" do |app|
       options = app.config.view_component
 
+      %i[generate preview_controller preview_route show_previews_source].each do |config_option|
+        options[config_option] ||= ViewComponent::Base.public_send(config_option)
+      end
+      options.instrumentation_enabled = false if options.instrumentation_enabled.nil?
       options.render_monkey_patch_enabled = true if options.render_monkey_patch_enabled.nil?
       options.show_previews = Rails.env.development? || Rails.env.test? if options.show_previews.nil?
-      options.show_previews_source ||= ViewComponent::Base.show_previews_source
       options.instrumentation_enabled = false if options.instrumentation_enabled.nil?
-      options.preview_route ||= ViewComponent::Base.preview_route
-      options.preview_controller ||= ViewComponent::Base.preview_controller
 
       if options.show_previews
+        # This is still necessary because when `config.view_component` is declared, `Rails.root` is unspecified.
         options.preview_paths << "#{Rails.root}/test/components/previews" if defined?(Rails.root) && Dir.exist?(
           "#{Rails.root}/test/components/previews"
         )
 
-        if options.preview_path.present?
-          ViewComponent::Deprecation.warn(
-            "`preview_path` will be removed in v3.0.0. Use `preview_paths` instead."
-          )
-          options.preview_paths << options.preview_path
-        end
-
         if options.show_previews_source
           require "method_source"
 
@@ -41,10 +36,6 @@ module ViewComponent
           end
         end
       end
-
-      ActiveSupport.on_load(:view_component) do
-        options.each { |k, v| send("#{k}=", v) if respond_to?("#{k}=") }
-      end
     end
 
     initializer "view_component.enable_instrumentation" do |app|
@@ -72,12 +63,6 @@ module ViewComponent
       end
     end
 
-    initializer "view_component.compile_config_methods" do
-      ActiveSupport.on_load(:view_component) do
-        config.compile_methods! if config.respond_to?(:compile_methods!)
-      end
-    end
-
     initializer "view_component.monkey_patch_render" do |app|
       next if Rails.version.to_f >= 6.1 || !app.config.view_component.render_monkey_patch_enabled
 
@@ -94,7 +79,7 @@ module ViewComponent
       end
     end
 
-    initializer "view_component.include_render_component" do |app|
+    initializer "view_component.include_render_component" do |_app|
       next if Rails.version.to_f >= 6.1
 
       ActiveSupport.on_load(:action_view) do
@@ -116,7 +101,7 @@ module ViewComponent
       end
     end
 
-    initializer "compiler mode" do |app|
+    initializer "compiler mode" do |_app|
       ViewComponent::Compiler.mode = if Rails.env.development? || Rails.env.test?
         ViewComponent::Compiler::DEVELOPMENT_MODE
       else
@@ -160,7 +145,7 @@ unless defined?(ViewComponent::Base)
 
   ViewComponent::Deprecation.warn(
     "This manually engine loading is deprecated and will be removed in v3.0.0. " \
-    "Remove `require \"view_component/engine\"`."
+    'Remove `require "view_component/engine"`.'
   )
 
   require "view_component"

lib/view_component/previewable.rb

@@ -1,62 +0,0 @@
-# frozen_string_literal: true
-
-require "active_support/concern"
-
-module ViewComponent
-  module Previewable
-    extend ActiveSupport::Concern
-
-    included do
-      # Enable or disable component previews:
-      #
-      #     config.view_component.show_previews = true
-      #
-      # Defaults to `true` in development.
-      #
-      mattr_accessor :show_previews, instance_writer: false
-
-      # Enable or disable source code previews in component previews:
-      #
-      #     config.view_component.show_previews_source = true
-      #
-      # Defaults to `false`.
-      #
-      mattr_accessor :show_previews_source, instance_writer: false, default: false
-
-      # Set a custom default layout used for preview index and individual previews:
-      #
-      #     config.view_component.default_preview_layout = "component_preview"
-      #
-      mattr_accessor :default_preview_layout, instance_writer: false
-
-      # Set the location of component previews:
-      #
-      #     config.view_component.preview_paths << "#{Rails.root}/lib/component_previews"
-      #
-      mattr_accessor :preview_paths, instance_writer: false
-
-      # @deprecated Use `preview_paths` instead. Will be removed in v3.0.0.
-      mattr_accessor :preview_path, instance_writer: false
-
-      # Set the entry route for component previews:
-      #
-      #     config.view_component.preview_route = "/previews"
-      #
-      # Defaults to `/rails/view_components` when `show_previews` is enabled.
-      #
-      mattr_accessor :preview_route, instance_writer: false do
-        "/rails/view_components"
-      end
-
-      # Set the controller used for previewing components:
-      #
-      #     config.view_component.preview_controller = "MyPreviewController"
-      #
-      # Defaults to `ViewComponentsController`.
-      #
-      mattr_accessor :preview_controller, instance_writer: false do
-        "ViewComponentsController"
-      end
-    end
-  end
-end

lib/view_component/render_preview_helper.rb

@@ -22,9 +22,7 @@ module ViewComponent
     def render_preview(name)
       begin
         preview_klass = if respond_to?(:described_class)
-          if described_class.nil?
-            raise "`render_preview` expected a described_class, but it is nil."
-          end
+          raise "`render_preview` expected a described_class, but it is nil." if described_class.nil?
 
           "#{described_class}Preview"
         else
@@ -32,12 +30,10 @@ module ViewComponent
         end
         preview_klass = preview_klass.constantize
       rescue NameError
-        raise NameError.new(
-          "`render_preview` expected to find #{preview_klass}, but it does not exist."
-        )
+        raise NameError, "`render_preview` expected to find #{preview_klass}, but it does not exist."
       end
 
-      previews_controller = build_controller(ViewComponent::Base.preview_controller.constantize)
+      previews_controller = build_controller(Rails.application.config.view_component.preview_controller.constantize)
       previews_controller.request.params[:path] = "#{preview_klass.preview_name}/#{name}"
       previews_controller.response = ActionDispatch::Response.new
       result = previews_controller.previews

test/sandbox/app/components/container_component.rb

@@ -2,7 +2,7 @@
 
 class ContainerComponent < ViewComponent::Base
   def call
-    if ViewComponent::Base.render_monkey_patch_enabled || Rails.version.to_f >= 6.1
+    if Rails.application.config.view_component.render_monkey_patch_enabled || Rails.version.to_f >= 6.1
       render HelpersProxyComponent.new
     else
       render_component HelpersProxyComponent.new

test/sandbox/config/application.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require File.expand_path("../boot", __FILE__)
+require File.expand_path("boot", __dir__)
 
 require "active_model/railtie"
 require "action_controller/railtie"

test/sandbox/test/config_test.rb

@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+module ViewComponent
+  class ConfigTest < TestCase
+    def setup
+      @config = ViewComponent::Config.new
+    end
+
+    def test_defaults_are_correct
+      assert_equal @config.generate, {}
+      assert_equal @config.preview_controller, "ViewComponentsController"
+      assert_equal @config.preview_route, "/rails/view_components"
+      assert_equal @config.show_previews_source, false
+      assert_equal @config.instrumentation_enabled, false
+      assert_equal @config.render_monkey_patch_enabled, true
+      assert_equal @config.show_previews, true
+      assert_equal @config.preview_paths, ["#{Rails.root}/test/components/previews"]
+    end
+
+    def test_preview_path_alias
+      @config.preview_path << "some/new/path"
+      assert_equal @config.preview_paths, @config.preview_path
+    end
+
+    def test_preview_path_setter_alias
+      old_value = @config.preview_path
+      @config.preview_path = "some/new/path"
+      assert_equal @config.preview_path, ["some/new/path"]
+      @config.preview_path = old_value
+    end
+
+    def test_all_methods_are_documented
+      require "yard"
+      require "rake"
+      YARD::Rake::YardocTask.new
+      Rake::Task["yard"].execute
+      configuration_methods_to_document = YARD::RegistryStore.new.tap do |store|
+        store.load!(".yardoc")
+      end.get("ViewComponent::Config").meths.select(&:reader?).reject { |meth| meth.name == :config }
+      default_options = ViewComponent::Config.defaults.keys
+      accessors = ViewComponent::Config.instance_methods(false).reject do |method_name|
+        method_name.to_s.end_with?("=") || method_name == :method_missing
+      end
+      options_defined_on_instance = Set[*default_options, *accessors]
+      assert options_defined_on_instance.subset?(Set[*configuration_methods_to_document.map(&:name)]),
+        "Not all configuration options are documented: #{configuration_methods_to_document.map(&:name) - options_defined_on_instance.to_a}"
+      assert configuration_methods_to_document.map(&:docstring).all?(&:present?),
+        "Configuration options are missing docstrings."
+    end
+  end
+end

test/sandbox/test/generators/locale_generator_test.rb

@@ -130,9 +130,7 @@ class LocaleGeneratorTest < Rails::Generators::TestCase
 
   private
 
-  def with_generate_distinct_locale_files
-    ViewComponent::Base.generate.distinct_locale_files = true
-    yield
-    ViewComponent::Base.generate.distinct_locale_files = false
+  def with_generate_distinct_locale_files(&block)
+    with_generate_option(:distinct_locale_files, true, &block)
   end
 end

test/sandbox/test/integration_test.rb

@@ -666,4 +666,19 @@ class IntegrationTest < ActionDispatch::IntegrationTest
     ActionController::Base.perform_caching = false
     Rails.cache.clear
   end
+
+  def test_config_options_shared_between_base_and_engine
+    Rails.application.config.view_component.yield_self do |config|
+      {
+        generate: config.generate.dup.tap { |c| c.sidecar = true },
+        preview_controller: "SomeOtherController",
+        preview_route: "/some/other/route",
+        show_previews_source: true
+      }.each do |option, value|
+        with_config_option(option, value) do
+          assert_equal(config.public_send(option), ViewComponent::Base.public_send(option))
+        end
+      end
+    end
+  end
 end

test/sandbox/test/preview_helper_test.rb

@@ -94,7 +94,7 @@ class PreviewHelperTest < ActiveSupport::TestCase
 
         mock = Minitest::Mock.new
         mock.expect :map, [expected_template_path]
-        ViewComponent::Base.stub(:preview_paths, mock) do
+        Rails.application.config.view_component.stub(:preview_paths, mock) do
           File.stub(:read, expected_source, [expected_template_path]) do
             template_data = PreviewHelper.find_template_data(
               lookup_context: lookup_context,
@@ -120,7 +120,7 @@ class PreviewHelperTest < ActiveSupport::TestCase
 
       mock = Minitest::Mock.new
       mock.expect :map, []
-      ViewComponent::Base.stub :preview_paths, mock do
+      Rails.application.config.view_component.stub :preview_paths, mock do
         exception = assert_raises RuntimeError do
           PreviewHelper.find_template_data(
             lookup_context: lookup_context,
@@ -144,7 +144,7 @@ class PreviewHelperTest < ActiveSupport::TestCase
 
       mock = Minitest::Mock.new
       mock.expect :map, [template_identifier + ".html.haml", template_identifier + ".html.erb"]
-      ViewComponent::Base.stub :preview_paths, mock do
+      Rails.application.config.view_component.stub :preview_paths, mock do
         exception = assert_raises RuntimeError do
           PreviewHelper.find_template_data(
             lookup_context: lookup_context,

test/test_helper.rb

@@ -35,19 +35,24 @@ ENV["RAILS_ENV"] = "test"
 require "view_component/deprecation"
 ViewComponent::Deprecation.behavior = :silence
 
-require File.expand_path("../sandbox/config/environment.rb", __FILE__)
+require File.expand_path("sandbox/config/environment.rb", __dir__)
 require "rails/test_help"
 
+def with_config_option(option_name, new_value)
+  old_value = Rails.application.config.view_component.public_send(option_name)
+  Rails.application.config.view_component.public_send("#{option_name}=", new_value)
+  yield
+ensure
+  Rails.application.config.view_component.public_send("#{option_name}=", old_value)
+end
+
 # Sets custom preview paths in tests.
 #
 # @param new_value [Array<String>] List of preview paths
 # @yield Test code to run
 # @return [void]
-def with_preview_paths(new_value)
-  old_value = Rails.application.config.view_component.preview_paths
-  Rails.application.config.view_component.preview_paths = new_value
-  yield
-  Rails.application.config.view_component.preview_paths = old_value
+def with_preview_paths(new_value, &block)
+  with_config_option(:preview_paths, new_value, &block)
 end
 
 def with_preview_route(new_value)
@@ -55,6 +60,7 @@ def with_preview_route(new_value)
   Rails.application.config.view_component.preview_route = new_value
   app.reloader.reload!
   yield
+ensure
   Rails.application.config.view_component.preview_route = old_value
   app.reloader.reload!
 end
@@ -64,24 +70,17 @@ def with_preview_controller(new_value)
   Rails.application.config.view_component.preview_controller = new_value
   app.reloader.reload!
   yield
+ensure
   Rails.application.config.view_component.preview_controller = old_value
   app.reloader.reload!
 end
 
-def with_custom_component_path(new_value)
-  old_value = ViewComponent::Base.view_component_path
-  ViewComponent::Base.view_component_path = new_value
-  yield
-ensure
-  ViewComponent::Base.view_component_path = old_value
+def with_custom_component_path(new_value, &block)
+  with_config_option(:view_component_path, new_value, &block)
 end
 
-def with_custom_component_parent_class(new_value)
-  old_value = ViewComponent::Base.component_parent_class
-  ViewComponent::Base.component_parent_class = new_value
-  yield
-ensure
-  ViewComponent::Base.component_parent_class = old_value
+def with_custom_component_parent_class(new_value, &block)
+  with_config_option(:component_parent_class, new_value, &block)
 end
 
 def with_application_component_class
@@ -91,12 +90,16 @@ ensure
   Object.send(:remove_const, :ApplicationComponent)
 end
 
-def with_generate_sidecar(enabled)
-  old_value = ViewComponent::Base.generate.sidecar
-  ViewComponent::Base.generate.sidecar = enabled
+def with_generate_option(config_option, value)
+  old_value = Rails.application.config.view_component.generate[config_option]
+  Rails.application.config.view_component.generate[config_option] = value
   yield
 ensure
-  ViewComponent::Base.generate.sidecar = old_value
+  Rails.application.config.view_component.generate[config_option] = old_value
+end
+
+def with_generate_sidecar(enabled, &block)
+  with_generate_option(:sidecar, enabled, &block)
 end
 
 def with_new_cache
@@ -111,15 +114,13 @@ ensure
   ViewComponent::CompileCache.cache = old_cache
 end
 
-def without_template_annotations
+def without_template_annotations(&block)
   if ActionView::Base.respond_to?(:annotate_rendered_view_with_filenames)
     old_value = ActionView::Base.annotate_rendered_view_with_filenames
     ActionView::Base.annotate_rendered_view_with_filenames = false
     app.reloader.reload! if defined?(app)
 
-    with_new_cache do
-      yield
-    end
+    with_new_cache(&block)
 
     ActionView::Base.annotate_rendered_view_with_filenames = old_value
     app.reloader.reload! if defined?(app)
@@ -139,19 +140,12 @@ def modify_file(file, content)
   end
 end
 
-def with_default_preview_layout(layout)
-  old_value = ViewComponent::Base.default_preview_layout
-  ViewComponent::Base.default_preview_layout = layout
-  yield
-  ViewComponent::Base.default_preview_layout = old_value
+def with_default_preview_layout(layout, &block)
+  with_config_option(:default_preview_layout, layout, &block)
 end
 
-def with_render_monkey_patch_config(enabled)
-  old_default = ViewComponent::Base.render_monkey_patch_enabled
-  ViewComponent::Base.render_monkey_patch_enabled = enabled
-  yield
-ensure
-  ViewComponent::Base.render_monkey_patch_enabled = old_default
+def with_render_monkey_patch_config(enabled, &block)
+  with_config_option(:render_monkey_patch_enabled, enabled, &block)
 end
 
 def with_compiler_mode(mode)