Extract caching into its own module.

lib/active_model/serializer.rb

@@ -4,6 +4,7 @@ require 'active_model/serializer/array_serializer'
 require 'active_model/serializer/include_tree'
 require 'active_model/serializer/associations'
 require 'active_model/serializer/attributes'
+require 'active_model/serializer/caching'
 require 'active_model/serializer/configuration'
 require 'active_model/serializer/fieldset'
 require 'active_model/serializer/lint'
@@ -15,63 +16,19 @@ module ActiveModel
     include Configuration
     include Associations
     include Attributes
+    include Caching
     require 'active_model/serializer/adapter'
 
-    # Matches
-    #  "c:/git/emberjs/ember-crm-backend/app/serializers/lead_serializer.rb:1:in `<top (required)>'"
-    #  AND
-    #  "/c/git/emberjs/ember-crm-backend/app/serializers/lead_serializer.rb:1:in `<top (required)>'"
-    #  AS
-    #  c/git/emberjs/ember-crm-backend/app/serializers/lead_serializer.rb
-    CALLER_FILE = /
-      \A       # start of string
-      .+       # file path (one or more characters)
-      (?=      # stop previous match when
-        :\d+     # a colon is followed by one or more digits
-        :in      # followed by a colon followed by in
-      )
-    /x
-
-    # Hashes contents of file for +_cache_digest+
-    def self.digest_caller_file(caller_line)
-      serializer_file_path = caller_line[CALLER_FILE]
-      serializer_file_contents = IO.read(serializer_file_path)
-      Digest::MD5.hexdigest(serializer_file_contents)
-    rescue TypeError, Errno::ENOENT
-      warn <<-EOF.strip_heredoc
-       Cannot digest non-existent file: '#{caller_line}'.
-       Please set `::_cache_digest` of the serializer
-       if you'd like to cache it.
-       EOF
-      ''.freeze
-    end
-
     with_options instance_writer: false, instance_reader: false do |serializer|
       serializer.class_attribute :_type, instance_reader: true
       serializer.class_attribute :_links # @api private : links definitions, @see Serializer#link
       self._links ||= {}
-      serializer.class_attribute :_cache         # @api private : the cache object
-      serializer.class_attribute :_fragmented    # @api private : @see ::fragmented
-      serializer.class_attribute :_cache_key     # @api private : when present, is first item in cache_key
-      serializer.class_attribute :_cache_only    # @api private : when fragment caching, whitelists cached_attributes. Cannot combine with except
-      serializer.class_attribute :_cache_except  # @api private : when fragment caching, blacklists cached_attributes. Cannot combine with only
-      serializer.class_attribute :_cache_options # @api private : used by CachedSerializer, passed to _cache.fetch
-      #  _cache_options include:
-      #    expires_in
-      #    compress
-      #    force
-      #    race_condition_ttl
-      #  Passed to ::_cache as
-      #    serializer._cache.fetch(cache_key, @klass._cache_options)
-      serializer.class_attribute :_cache_digest # @api private : Generated
     end
 
     # Serializers inherit _attribute_mappings, _reflections, and _links.
     # Generates a unique digest for each serializer at load.
     def self.inherited(base)
-      caller_line = caller.first
       base._links = _links.dup
-      base._cache_digest = digest_caller_file(caller_line)
       super
     end
 
@@ -86,43 +43,6 @@ module ActiveModel
       _links[name] = block || value
     end
 
-    # @api private
-    # Used by FragmentCache on the CachedSerializer
-    #  to call attribute methods on the fragmented cached serializer.
-    def self.fragmented(serializer)
-      self._fragmented = serializer
-    end
-
-    # Enables a serializer to be automatically cached
-    #
-    # Sets +::_cache+ object to <tt>ActionController::Base.cache_store</tt>
-    #   when Rails.configuration.action_controller.perform_caching
-    #
-    # @params options [Hash] with valid keys:
-    #   key            : @see ::_cache_key
-    #   only           : @see ::_cache_only
-    #   except         : @see ::_cache_except
-    #   skip_digest    : does not include digest in cache_key
-    #   all else       : @see ::_cache_options
-    #
-    # @example
-    #   class PostSerializer < ActiveModel::Serializer
-    #     cache key: 'post', expires_in: 3.hours
-    #     attributes :title, :body
-    #
-    #     has_many :comments
-    #   end
-    #
-    # @todo require less code comments. See
-    # https://github.com/rails-api/active_model_serializers/pull/1249#issuecomment-146567837
-    def self.cache(options = {})
-      self._cache = ActiveModelSerializers.config.cache_store if ActiveModelSerializers.config.perform_caching
-      self._cache_key = options.delete(:key)
-      self._cache_only = options.delete(:only)
-      self._cache_except = options.delete(:except)
-      self._cache_options = (options.empty?) ? nil : options
-    end
-
     # @param resource [ActiveRecord::Base, ActiveModelSerializers::Model]
     # @return [ActiveModel::Serializer]
     #   Preferentially returns
@@ -145,12 +65,6 @@ module ActiveModel
       ActiveModel::Serializer::Adapter.lookup(config.adapter)
     end
 
-    # Used to cache serializer name => serializer class
-    # when looked up by Serializer.get_serializer_for.
-    def self.serializers_cache
-      @serializers_cache ||= ThreadSafe::Cache.new
-    end
-
     # @api private
     def self.serializer_lookup_chain_for(klass)
       chain = []
@@ -165,6 +79,12 @@ module ActiveModel
       chain
     end
 
+    # Used to cache serializer name => serializer class
+    # when looked up by Serializer.get_serializer_for.
+    def self.serializers_cache
+      @serializers_cache ||= ThreadSafe::Cache.new
+    end
+
     # @api private
     # Find a serializer from a class and caches the lookup.
     # Preferentially retuns:

lib/active_model/serializer/caching.rb

@@ -0,0 +1,100 @@
+module ActiveModel
+  class Serializer
+    module Caching
+      extend ActiveSupport::Concern
+
+      included do
+        with_options instance_writer: false, instance_reader: false do |serializer|
+          serializer.class_attribute :_cache         # @api private : the cache object
+          serializer.class_attribute :_fragmented    # @api private : @see ::fragmented
+          serializer.class_attribute :_cache_key     # @api private : when present, is first item in cache_key
+          serializer.class_attribute :_cache_only    # @api private : when fragment caching, whitelists cached_attributes. Cannot combine with except
+          serializer.class_attribute :_cache_except  # @api private : when fragment caching, blacklists cached_attributes. Cannot combine with only
+          serializer.class_attribute :_cache_options # @api private : used by CachedSerializer, passed to _cache.fetch
+          #  _cache_options include:
+          #    expires_in
+          #    compress
+          #    force
+          #    race_condition_ttl
+          #  Passed to ::_cache as
+          #    serializer._cache.fetch(cache_key, @klass._cache_options)
+          serializer.class_attribute :_cache_digest # @api private : Generated
+        end
+      end
+
+      # Matches
+      #  "c:/git/emberjs/ember-crm-backend/app/serializers/lead_serializer.rb:1:in `<top (required)>'"
+      #  AND
+      #  "/c/git/emberjs/ember-crm-backend/app/serializers/lead_serializer.rb:1:in `<top (required)>'"
+      #  AS
+      #  c/git/emberjs/ember-crm-backend/app/serializers/lead_serializer.rb
+      CALLER_FILE = /
+        \A       # start of string
+        .+       # file path (one or more characters)
+        (?=      # stop previous match when
+          :\d+     # a colon is followed by one or more digits
+          :in      # followed by a colon followed by in
+        )
+      /x
+
+      module ClassMethods
+        def inherited(base)
+          super
+          caller_line = caller[1]
+          base._cache_digest = digest_caller_file(caller_line)
+        end
+
+        # Hashes contents of file for +_cache_digest+
+        def digest_caller_file(caller_line)
+          serializer_file_path = caller_line[CALLER_FILE]
+          serializer_file_contents = IO.read(serializer_file_path)
+          Digest::MD5.hexdigest(serializer_file_contents)
+        rescue TypeError, Errno::ENOENT
+          warn <<-EOF.strip_heredoc
+            Cannot digest non-existent file: '#{caller_line}'.
+            Please set `::_cache_digest` of the serializer
+            if you'd like to cache it.
+            EOF
+          ''.freeze
+        end
+
+        # @api private
+        # Used by FragmentCache on the CachedSerializer
+        #  to call attribute methods on the fragmented cached serializer.
+        def fragmented(serializer)
+          self._fragmented = serializer
+        end
+
+        # Enables a serializer to be automatically cached
+        #
+        # Sets +::_cache+ object to <tt>ActionController::Base.cache_store</tt>
+        #   when Rails.configuration.action_controller.perform_caching
+        #
+        # @params options [Hash] with valid keys:
+        #   key            : @see ::_cache_key
+        #   only           : @see ::_cache_only
+        #   except         : @see ::_cache_except
+        #   skip_digest    : does not include digest in cache_key
+        #   all else       : @see ::_cache_options
+        #
+        # @example
+        #   class PostSerializer < ActiveModel::Serializer
+        #     cache key: 'post', expires_in: 3.hours
+        #     attributes :title, :body
+        #
+        #     has_many :comments
+        #   end
+        #
+        # @todo require less code comments. See
+        # https://github.com/rails-api/active_model_serializers/pull/1249#issuecomment-146567837
+        def cache(options = {})
+          self._cache = ActiveModelSerializers.config.cache_store if ActiveModelSerializers.config.perform_caching
+          self._cache_key = options.delete(:key)
+          self._cache_only = options.delete(:only)
+          self._cache_except = options.delete(:except)
+          self._cache_options = (options.empty?) ? nil : options
+        end
+      end
+    end
+  end
+end