Slightly reorganize lookup context modules in order to better isolate cache responsibilities.

actionpack/lib/action_view/lookup_context.rb

 require 'active_support/core_ext/array/wrap'
 require 'active_support/core_ext/object/blank'
+require 'active_support/core_ext/module/remove_method'
 
 module ActionView
   # = Action View Lookup Context
@@ -17,12 +18,11 @@ class LookupContext #:nodoc:
     mattr_accessor :registered_details
     self.registered_details = []
 
-    mattr_accessor :registered_detail_setters
-    self.registered_detail_setters = []
-
     def self.register_detail(name, options = {}, &block)
       self.registered_details << name
-      self.registered_detail_setters << [name, "#{name}="]
+
+      initialize = registered_details.map { |n| "self.#{n} = details[:#{n}]" }
+      update     = registered_details.map { |n| "self.#{n} = details[:#{n}] if details.key?(:#{n})" }
 
       Accessors.send :define_method, :"_#{name}_defaults", &block
       Accessors.module_eval <<-METHOD, __FILE__, __LINE__ + 1
@@ -34,6 +34,16 @@ def #{name}=(value)
           value = Array.wrap(value.presence || _#{name}_defaults)
           _set_detail(:#{name}, value) if value != @details[:#{name}]
         end
+
+        remove_possible_method :initialize_details
+        def initialize_details(details)
+          #{initialize.join("\n")}
+        end
+
+        remove_possible_method :update_details
+        def update_details(details)
+          #{update.join("\n")}
+        end
       METHOD
     end
 
@@ -60,18 +70,53 @@ def initialize
       end
     end
 
-    def initialize(view_paths, details = {}, prefixes = [])
-      @details, @details_key = { :handlers => default_handlers }, nil
-      @frozen_formats, @skip_default_locale = false, false
-      @cache = true
-      @prefixes = prefixes
+    # Add caching behavior on top of Details.
+    module DetailsCache
+      attr_accessor :cache
 
-      self.view_paths = view_paths
-      self.registered_detail_setters.each do |key, setter|
-        send(setter, details[key])
+      # Calculate the details key. Remove the handlers from calculation to improve performance
+      # since the user cannot modify it explicitly.
+      def details_key #:nodoc:
+        @details_key ||= DetailsKey.get(@details) if @cache
+      end
+
+      # Temporary skip passing the details_key forward.
+      def disable_cache
+        old_value, @cache = @cache, false
+        yield
+      ensure
+        @cache = old_value
+      end
+
+      # Update the details keys by merging the given hash into the current
+      # details hash. If a block is given, the details are modified just during
+      # the execution of the block and reverted to the previous value after.
+      def update_details(new_details)
+        if block_given?
+          old_details = @details.dup
+          super
+
+          begin
+            yield
+          ensure
+            @details_key = nil
+            @details = old_details
+          end
+        else
+          super
+        end
+      end
+
+    protected
+
+      def _set_detail(key, value)
+        @details_key = nil
+        @details = @details.dup if @details.frozen?
+        @details[key] = value.freeze
       end
     end
 
+    # Helpers related to template lookup using the lookup context information.
     module ViewPaths
       attr_reader :view_paths
 
@@ -141,111 +186,77 @@ def handlers_regexp #:nodoc:
       end
     end
 
-    module Details
-      attr_accessor :cache
-
-      # Calculate the details key. Remove the handlers from calculation to improve performance
-      # since the user cannot modify it explicitly.
-      def details_key #:nodoc:
-        @details_key ||= DetailsKey.get(@details) if @cache
-      end
-
-      # Temporary skip passing the details_key forward.
-      def disable_cache
-        old_value, @cache = @cache, false
-        yield
-      ensure
-        @cache = old_value
-      end
+    include Accessors
+    include DetailsCache
+    include ViewPaths
 
-      # Freeze the current formats in the lookup context. By freezing them, you are guaranteeing
-      # that next template lookups are not going to modify the formats. The controller can also
-      # use this, to ensure that formats won't be further modified (as it does in respond_to blocks).
-      def freeze_formats(formats, unless_frozen=false) #:nodoc:
-        return if unless_frozen && @frozen_formats
-        self.formats = formats
-        @frozen_formats = true
-      end
+    def initialize(view_paths, details = {}, prefixes = [])
+      @details, @details_key = { :handlers => default_handlers }, nil
+      @frozen_formats, @skip_default_locale = false, false
+      @cache = true
+      @prefixes = prefixes
 
-      # Overload formats= to expand ["*/*"] values and automatically
-      # add :html as fallback to :js.
-      def formats=(values)
-        if values
-          values.concat(_formats_defaults) if values.delete "*/*"
-          values << :html if values == [:js]
-        end
-        super(values)
-      end
+      self.view_paths = view_paths
+      initialize_details(details)
+    end
 
-      # Do not use the default locale on template lookup.
-      def skip_default_locale!
-        @skip_default_locale = true
-        self.locale = nil
-      end
+    # Freeze the current formats in the lookup context. By freezing them, you
+    # that next template lookups are not going to modify the formats. The con
+    # use this, to ensure that formats won't be further modified (as it does
+    def freeze_formats(formats, unless_frozen=false) #:nodoc:
+      return if unless_frozen && @frozen_formats
+      self.formats = formats
+      @frozen_formats = true
+    end
 
-      # Overload locale to return a symbol instead of array.
-      def locale
-        @details[:locale].first
+    # Override formats= to expand ["*/*"] values and automatically
+    # add :html as fallback to :js.
+    def formats=(values)
+      if values
+        values.concat(_formats_defaults) if values.delete "*/*"
+        values << :html if values == [:js]
       end
+      super(values)
+    end
 
-      # Overload locale= to also set the I18n.locale. If the current I18n.config object responds
-      # to original_config, it means that it's has a copy of the original I18n configuration and it's
-      # acting as proxy, which we need to skip.
-      def locale=(value)
-        if value
-          config = I18n.config.respond_to?(:original_config) ? I18n.config.original_config : I18n.config
-          config.locale = value
-        end
-
-        super(@skip_default_locale ? I18n.locale : _locale_defaults)
-      end
+    # Do not use the default locale on template lookup.
+    def skip_default_locale!
+      @skip_default_locale = true
+      self.locale = nil
+    end
 
-      # A method which only uses the first format in the formats array for layout lookup.
-      # This method plays straight with instance variables for performance reasons.
-      def with_layout_format
-        if formats.size == 1
-          yield
-        else
-          old_formats = formats
-          _set_detail(:formats, formats[0,1])
+    # Override locale to return a symbol instead of array.
+    def locale
+      @details[:locale].first
+    end
 
-          begin
-            yield
-          ensure
-            _set_detail(:formats, old_formats)
-          end
-        end
+    # Overload locale= to also set the I18n.locale. If the current I18n.config object responds
+    # to original_config, it means that it's has a copy of the original I18n configuration and it's
+    # acting as proxy, which we need to skip.
+    def locale=(value)
+      if value
+        config = I18n.config.respond_to?(:original_config) ? I18n.config.original_config : I18n.config
+        config.locale = value
       end
 
-      # Update the details keys by merging the given hash into the current
-      # details hash. If a block is given, the details are modified just during
-      # the execution of the block and reverted to the previous value after.
-      def update_details(new_details)
-        old_details = @details.dup
+      super(@skip_default_locale ? I18n.locale : _locale_defaults)
+    end
 
-        registered_detail_setters.each do |key, setter|
-          send(setter, new_details[key]) if new_details.key?(key)
-        end
+    # A method which only uses the first format in the formats array for layout lookup.
+    # This method plays straight with instance variables for performance reasons.
+    def with_layout_format
+      if formats.size == 1
+        yield
+      else
+        old_formats = formats
+        _set_detail(:formats, formats[0,1])
 
         begin
           yield
         ensure
-          @details_key = nil
-          @details = old_details
+          _set_detail(:formats, old_formats)
         end
       end
-
-    protected
-
-      def _set_detail(key, value)
-        @details_key = nil
-        @details = @details.dup if @details.frozen?
-        @details[key] = value.freeze
-      end
     end
-
-    include Accessors
-    include Details
-    include ViewPaths
   end
 end