Remove dependency on the Rails module

Some parts of the code guard against undefined Rails module,
but some parts do that in unsafe manner.

Good example: `defined?(Rails.env) && Rails.env`
Bad example: `defined?(Rails) && Rails.env`

There are gems, that define `module Rails` to extend it, but then it is
incomplete and causes failures.

This change unifies accessing Rails module with proper `defines?`
guarding against incomplete definition of the Rails module.

Author: mikz

docs/CHANGELOG.md

@@ -13,6 +13,9 @@ nav_order: 6
 * Add Carwow to list of companies using ViewComponent.
 
     *Tom Lord*
+* ViewComponent now works without `rails` and `railties` gems loaded.
+
+    *Michal Cichra*
 
 ## 4.0.2
 

lib/view_component.rb

@@ -16,7 +16,7 @@ module ViewComponent
   autoload :Preview
   autoload :Translatable
 
-  if Rails.env.test?
+  if defined?(Rails.env) && Rails.env.test?
     autoload :TestHelpers
     autoload :SystemSpecHelpers
     autoload :SystemTestHelpers

lib/view_component/base.rb

@@ -47,7 +47,7 @@ def config
     end
 
     include ActionView::Helpers
-    include Rails.application.routes.url_helpers if defined?(Rails) && Rails.application
+    include Rails.application.routes.url_helpers if defined?(Rails.application.routes)
     include ERB::Escape
     include ActiveSupport::CoreExt::ERBUtil
 
@@ -302,7 +302,7 @@ def helpers
       @__vc_helpers ||= __vc_original_view_context || controller.view_context
     end
 
-    if ::Rails.env.development? || ::Rails.env.test?
+    if defined?(Rails.env) && (::Rails.env.development? || ::Rails.env.test?)
       # @private
       def method_missing(method_name, *args) # rubocop:disable Style/MissingRespondToMissing
         super
@@ -331,7 +331,7 @@ def view_cache_dependencies
       []
     end
 
-    if Rails::VERSION::MAJOR == 7 && Rails::VERSION::MINOR == 1
+    if defined?(Rails::VERSION) && (Rails::VERSION::MAJOR == 7 && Rails::VERSION::MINOR == 1)
       # Rails expects us to define `format` on all renderables,
       # but we do not know the `format` of a ViewComponent until runtime.
       def format

lib/view_component/collection.rb

@@ -20,7 +20,7 @@ def each(&block)
       components.each(&block)
     end
 
-    if Rails::VERSION::MAJOR == 7 && Rails::VERSION::MINOR == 1
+    if defined?(Rails::VERSION) && (Rails::VERSION::MAJOR == 7 && Rails::VERSION::MINOR == 1)
       # Rails expects us to define `format` on all renderables,
       # but we do not know the `format` of a ViewComponent until runtime.
       def format

lib/view_component/config.rb

@@ -163,7 +163,7 @@ def default_previews_options
         options = ActiveSupport::OrderedOptions.new
         options.controller = "ViewComponentsController"
         options.route = "/rails/view_components"
-        options.enabled = Rails.env.development? || Rails.env.test?
+        options.enabled = defined?(Rails.env) && (Rails.env.development? || Rails.env.test?)
         options.default_layout = nil
         options.paths = default_preview_paths
         options