1 files changed, 103 insertions, 0 deletions
diff --git a/actionpack/lib/action_controller/caching/fragments.rb b/actionpack/lib/action_controller/caching/fragments.rb
new file mode 100644
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+++ b/actionpack/lib/action_controller/caching/fragments.rb
@@ -0,0 +1,103 @@
+module ActionController
+  module Caching
+    # Fragment caching is used for caching various blocks within
+    # views without caching the entire action as a whole. This is
+    # useful when certain elements of an action change frequently or
+    # depend on complicated state while other parts rarely change or
+    # can be shared amongst multiple parties. The caching is done using
+    # the +cache+ helper available in the Action View. See
+    # ActionView::Helpers::CacheHelper for more information.
+    #
+    # While it's strongly recommended that you use key-based cache
+    # expiration (see links in CacheHelper for more information),
+    # it is also possible to manually expire caches. For example:
+    #
+    #   expire_fragment('name_of_cache')
+    module Fragments
+      # Given a key (as described in +expire_fragment+), returns
+      # a key suitable for use in reading, writing, or expiring a
+      # cached fragment. All keys are prefixed with <tt>views/</tt> and uses
+      # ActiveSupport::Cache.expand_cache_key for the expansion.
+      def fragment_cache_key(key)
+        ActiveSupport::Cache.expand_cache_key(key.is_a?(Hash) ? url_for(key).split("://").last : key, :views)
+      end
+
+      # Writes +content+ to the location signified by
+      # +key+ (see +expire_fragment+ for acceptable formats).
+      def write_fragment(key, content, options = nil)
+        return content unless cache_configured?
+
+        key = fragment_cache_key(key)
+        instrument_fragment_cache :write_fragment, key do
+          content = content.to_str
+          cache_store.write(key, content, options)
+        end
+        content
+      end
+
+      # Reads a cached fragment from the location signified by +key+
+      # (see +expire_fragment+ for acceptable formats).
+      def read_fragment(key, options = nil)
+        return unless cache_configured?
+
+        key = fragment_cache_key(key)
+        instrument_fragment_cache :read_fragment, key do
+          result = cache_store.read(key, options)
+          result.respond_to?(:html_safe) ? result.html_safe : result
+        end
+      end
+
+      # Check if a cached fragment from the location signified by
+      # +key+ exists (see +expire_fragment+ for acceptable formats).
+      def fragment_exist?(key, options = nil)
+        return unless cache_configured?
+        key = fragment_cache_key(key)
+
+        instrument_fragment_cache :exist_fragment?, key do
+          cache_store.exist?(key, options)
+        end
+      end
+
+      # Removes fragments from the cache.
+      #
+      # +key+ can take one of three forms:
+      #
+      # * String - This would normally take the form of a path, like
+      #   <tt>pages/45/notes</tt>.
+      # * Hash - Treated as an implicit call to +url_for+, like
+      #   <tt>{ controller: 'pages', action: 'notes', id: 45}</tt>
+      # * Regexp - Will remove any fragment that matches, so
+      #   <tt>%r{pages/\d*/notes}</tt> might remove all notes. Make sure you
+      #   don't use anchors in the regex (<tt>^</tt> or <tt>$</tt>) because
+      #   the actual filename matched looks like
+      #   <tt>./cache/filename/path.cache</tt>. Note: Regexp expiration is
+      #   only supported on caches that can iterate over all keys (unlike
+      #   memcached).
+      #
+      # +options+ is passed through to the cache store's +delete+
+      # method (or <tt>delete_matched</tt>, for Regexp keys).
+      def expire_fragment(key, options = nil)
+        return unless cache_configured?
+        key = fragment_cache_key(key) unless key.is_a?(Regexp)
+
+        instrument_fragment_cache :expire_fragment, key do
+          if key.is_a?(Regexp)
+            cache_store.delete_matched(key, options)
+          else
+            cache_store.delete(key, options)
+          end
+        end
+      end
+
+      def instrument_fragment_cache(name, key) # :nodoc:
+        payload = {
+          controller: controller_name,
+          action: action_name,
+          key: key
+        }
+
+        ActiveSupport::Notifications.instrument("#{name}.action_controller", payload) { yield }
+      end
+    end
+  end
+end