1 files changed, 107 insertions, 10 deletions

diff --git a/actionview/lib/action_view/base.rb b/actionview/lib/action_view/base.rb
index d41fe2a608..c4565ca272 100644
--- a/actionview/lib/action_view/base.rb
+++ b/actionview/lib/action_view/base.rb
@@ -3,6 +3,7 @@
 require "active_support/core_ext/module/attr_internal"
 require "active_support/core_ext/module/attribute_accessors"
 require "active_support/ordered_options"
+require "active_support/deprecation"
 require "action_view/log_subscriber"
 require "action_view/helpers"
 require "action_view/context"
@@ -179,37 +180,133 @@ module ActionView #:nodoc:
       def xss_safe? #:nodoc:
         true
       end
+
+      def with_empty_template_cache # :nodoc:
+        subclass = Class.new(self) {
+          # We can't implement these as self.class because subclasses will
+          # share the same template cache as superclasses, so "changed?" won't work
+          # correctly.
+          define_method(:compiled_method_container)           { subclass }
+          define_singleton_method(:compiled_method_container) { subclass }
+        }
+      end
+
+      def changed?(other) # :nodoc:
+        compiled_method_container != other.compiled_method_container
+      end
     end
 
-    attr_accessor :view_renderer
+    attr_reader :view_renderer, :lookup_context
     attr_internal :config, :assigns
 
-    delegate :lookup_context, to: :view_renderer
     delegate :formats, :formats=, :locale, :locale=, :view_paths, :view_paths=, to: :lookup_context
 
     def assign(new_assigns) # :nodoc:
       @_assigns = new_assigns.each { |key, value| instance_variable_set("@#{key}", value) }
     end
 
-    def initialize(context = nil, assigns = {}, controller = nil, formats = nil) #:nodoc:
+    # :stopdoc:
+
+    def self.build_lookup_context(context)
+      case context
+      when ActionView::Renderer
+        context.lookup_context
+      when Array
+        ActionView::LookupContext.new(context)
+      when ActionView::PathSet
+        ActionView::LookupContext.new(context)
+      when nil
+        ActionView::LookupContext.new([])
+      else
+        raise NotImplementedError, context.class.name
+      end
+    end
+
+    def self.empty
+      with_view_paths([])
+    end
+
+    def self.with_view_paths(view_paths, assigns = {}, controller = nil)
+      with_context ActionView::LookupContext.new(view_paths), assigns, controller
+    end
+
+    def self.with_context(context, assigns = {}, controller = nil)
+      new context, assigns, controller
+    end
+
+    NULL = Object.new
+
+    # :startdoc:
+
+    def initialize(lookup_context = nil, assigns = {}, controller = nil, formats = NULL) #:nodoc:
       @_config = ActiveSupport::InheritableOptions.new
 
-      if context.is_a?(ActionView::Renderer)
-        @view_renderer = context
+      unless formats == NULL
+        ActiveSupport::Deprecation.warn <<~eowarn
+        Passing formats to ActionView::Base.new is deprecated
+        eowarn
+      end
+
+      case lookup_context
+      when ActionView::LookupContext
+        @lookup_context = lookup_context
       else
-        lookup_context = context.is_a?(ActionView::LookupContext) ?
-          context : ActionView::LookupContext.new(context)
-        lookup_context.formats  = formats if formats
-        lookup_context.prefixes = controller._prefixes if controller
-        @view_renderer = ActionView::Renderer.new(lookup_context)
+        ActiveSupport::Deprecation.warn <<~eowarn
+        ActionView::Base instances should be constructed with a lookup context,
+        assignments, and a controller.
+        eowarn
+        @lookup_context = self.class.build_lookup_context(lookup_context)
       end
 
+      @view_renderer = ActionView::Renderer.new @lookup_context
+      @current_template = nil
+
       @cache_hit = {}
       assign(assigns)
       assign_controller(controller)
       _prepare_context
     end
 
+    def run(method, template, locals, buffer, &block)
+      _old_output_buffer, _old_virtual_path, _old_template = @output_buffer, @virtual_path, @current_template
+      @current_template = template
+      @output_buffer = buffer
+      send(method, locals, buffer, &block)
+    ensure
+      @output_buffer, @virtual_path, @current_template = _old_output_buffer, _old_virtual_path, _old_template
+    end
+
+    def compiled_method_container
+      if self.class == ActionView::Base
+        ActiveSupport::Deprecation.warn <<~eowarn
+          ActionView::Base instances must implement `compiled_method_container`
+          or use the class method `with_empty_template_cache` for constructing
+          an ActionView::Base instances that has an empty cache.
+        eowarn
+      end
+
+      self.class
+    end
+
+    def in_rendering_context(options)
+      old_view_renderer  = @view_renderer
+      old_lookup_context = @lookup_context
+
+      if !lookup_context.html_fallback_for_js && options[:formats]
+        formats = Array(options[:formats])
+        if formats == [:js]
+          formats << :html
+        end
+        @lookup_context = lookup_context.with_prepended_formats(formats)
+        @view_renderer = ActionView::Renderer.new @lookup_context
+      end
+
+      yield @view_renderer
+    ensure
+      @view_renderer = old_view_renderer
+      @lookup_context = old_lookup_context
+    end
+
     ActiveSupport.run_load_hooks(:action_view, self)
   end
 end