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@@ -1,5 +1,7 @@
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 *Edge*
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+* Set config.action_view.warn_cache_misses = true to receive a warning if you perform an action that results in an expensive disk operation that could be cached [Josh Peek]
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+
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 * Refactor template preloading. New abstractions include Renderable mixins and a refactored Template class [Josh Peek]
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 * Changed ActionView::TemplateHandler#render API method signature to render(template, local_assigns = {}) [Josh Peek]

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@@ -431,7 +431,7 @@ module ActionController #:nodoc:
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       end
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       def view_paths=(value)
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-        @view_paths = ActionView::PathSet.new(Array(value)) if value
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+        @view_paths = ActionView::Base.process_view_paths(value) if value
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       end
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       # Adds a view_path to the front of the view_paths array.
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@@ -652,7 +652,7 @@ module ActionController #:nodoc:
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       end
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       def view_paths=(value)
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-        @template.view_paths = PathSet.new(value)
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+        @template.view_paths = ActionView::Base.process_view_paths(value)
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       end
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       # Adds a view_path to the front of the view_paths array.

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@@ -185,6 +185,10 @@ module ActionView #:nodoc:
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     @@debug_rjs = false
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     cattr_accessor :debug_rjs
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+    # A warning will be displayed whenever an action results in a cache miss on your view paths.
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+    @@warn_cache_misses = false
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+    cattr_accessor :warn_cache_misses
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+
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     attr_internal :request
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     delegate :request_forgery_protection_token, :template, :params, :session, :cookies, :response, :headers,
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@@ -212,6 +216,10 @@ module ActionView #:nodoc:
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       return helpers
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     end
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+    def self.process_view_paths(value)
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+      ActionView::PathSet.new(Array(value))
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+    end
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+
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     def initialize(view_paths = [], assigns_for_first_render = {}, controller = nil)#:nodoc:
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       @assigns = assigns_for_first_render
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       @assigns_added = nil
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@@ -222,7 +230,7 @@ module ActionView #:nodoc:
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     attr_reader :view_paths
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     def view_paths=(paths)
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-      @view_paths = PathSet.new(Array(paths))
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+      @view_paths = self.class.process_view_paths(paths)
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     end
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     # Renders the template present at <tt>template_path</tt> (relative to the view_paths array).
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@@ -311,7 +319,17 @@ module ActionView #:nodoc:
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         @template_format = :html
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         template
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       else
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-        Template.new(template_path, view_paths)
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+        template = Template.new(template_path, view_paths)
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+
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+        if self.class.warn_cache_misses && logger = ActionController::Base.logger
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+          logger.debug "[PERFORMANCE] Rendering a template that was " +
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+            "not found in view path. Templates outside the view path are " +
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+            "not cached and result in expensive disk operations. Move this " + 
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+            "file into #{view_paths.join(':')} or add the folder to your " + 
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+            "view path list"
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+        end
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+
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+        template
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       end
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     end
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@@ -1,7 +1,18 @@
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 module ActionView #:nodoc:
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   class PathSet < Array #:nodoc:
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     def self.type_cast(obj)
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-      obj.is_a?(String) ? Path.new(obj) : obj
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+      if obj.is_a?(String)
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+        if Base.warn_cache_misses && defined?(Rails) && Rails.initialized?
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+          Rails.logger.debug "[PERFORMANCE] Processing view path during a " +
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+            "request. This an expense disk operation that should be done at " +
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+            "boot. You can manually process this view path with " +
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+            "ActionView::Base.process_view_paths(#{obj.inspect}) and set it " +
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+            "as your view path"
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+        end
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+        Path.new(obj)
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+      else
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+        obj
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+      end
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     end
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     class Path #:nodoc: