When caching, return the object's cache_key up front if it's defined.

This will prevent objects PORO objects that don't have updated_at defined, from throwing an error.

Not as big a deal now that PORO objects can inherit ActiveModelSerializers::Model, but still necessary if it's not inherited for whatever reason.

Add the Adapter type to the cache key.

This prevents incorrect results when the same object is serialized with different adapters.

BF:

Cherry-pick of
bf4@040a97b
which was a squash of
https://github.com/rails-api/active_model_serializers/commits/f89ed71058322fe7dd35d5c8b209856f8e03ad14

from pr 1346

Author: kevintyll

lib/active_model/serializer/caching.rb

@@ -7,7 +7,7 @@ module Caching
         with_options instance_writer: false, instance_reader: false do |serializer|
           serializer.class_attribute :_cache         # @api private : the cache store
           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_key     # @api private : when present, is first item in cache_key.  Ignored if the serializable object defines #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
@@ -58,6 +58,10 @@ def digest_caller_file(caller_line)
           ''.freeze
         end
 
+        def _skip_digest?
+          _cache_options && _cache_options[:skip_digest]
+        end
+
         # @api private
         # Used by FragmentCache on the CachedSerializer
         #  to call attribute methods on the fragmented cached serializer.
@@ -142,6 +146,18 @@ def fragment_cache_enabled?
             (_cache_only && !_cache_except || !_cache_only && _cache_except)
         end
       end
+
+      # Use object's cache_key if available, else derive a key from the object
+      # Pass the `key` option to the `cache` declaration or override this method to customize the cache key
+      def cache_key
+        if object.respond_to?(:cache_key)
+          object.cache_key
+        else
+          object_time_safe = object.updated_at
+          object_time_safe = object_time_safe.strftime('%Y%m%d%H%M%S%9N') if object_time_safe.respond_to?(:strftime)
+          "#{self.class._cache_key}/#{object.id}-#{object_time_safe}"
+        end
+      end
     end
   end
 end

lib/active_model_serializers/adapter/base.rb

@@ -8,13 +8,21 @@ def self.inherited(subclass)
         ActiveModelSerializers::Adapter.register(subclass)
       end
 
+      def self.name
+        to_s.demodulize
+      end
+
       attr_reader :serializer, :instance_options
 
       def initialize(serializer, options = {})
         @serializer = serializer
         @instance_options = options
       end
 
+      def name
+        self.class.name
+      end
+
       def serializable_hash(_options = nil)
         fail NotImplementedError, 'This is an abstract method. Should be implemented at the concrete adapter.'
       end

lib/active_model_serializers/cached_serializer.rb

@@ -1,13 +1,16 @@
 module ActiveModelSerializers
   class CachedSerializer
+    UndefinedCacheKey = Class.new(StandardError)
+
     def initialize(serializer)
       @cached_serializer = serializer
-      @klass             = @cached_serializer.class
+      return unless cached? && !@cached_serializer.object.respond_to?(:cache_key) && @klass._cache_key.blank?
+      fail(UndefinedCacheKey, "#{@cached_serializer.object} must define #cache_key, or the cache_key option must be passed into cache on #{@cached_serializer}")
     end
 
     def cache_check(adapter_instance)
       if cached?
-        @klass._cache.fetch(cache_key, @klass._cache_options) do
+        @klass._cache.fetch(cache_key(adapter_instance), @klass._cache_options) do
           yield
         end
       elsif fragment_cached?
@@ -25,21 +28,16 @@ def fragment_cached?
       @klass.fragment_cache_enabled?
     end
 
-    def cache_key
+    def cache_key(adapter_instance)
       return @cache_key if defined?(@cache_key)
 
       parts = []
-      parts << object_cache_key
-      parts << @klass._cache_digest unless @klass._cache_options && @klass._cache_options[:skip_digest]
+      parts << @cached_serializer.cache_key
+      parts << adapter_instance.name.underscore
+      parts << @klass._cache_digest unless @klass._skip_digest?
       @cache_key = parts.join('/')
     end
 
-    def object_cache_key
-      object_time_safe = @cached_serializer.object.updated_at
-      object_time_safe = object_time_safe.strftime('%Y%m%d%H%M%S%9N') if object_time_safe.respond_to?(:strftime)
-      @klass._cache_key ? "#{@klass._cache_key}/#{@cached_serializer.object.id}-#{object_time_safe}" : @cached_serializer.object.cache_key
-    end
-
     # find all cache_key for the collection_serializer
     # @param collection_serializer
     # @param include_tree

test/cache_test.rb

@@ -4,6 +4,21 @@
 
 module ActiveModelSerializers
   class CacheTest < ActiveSupport::TestCase
+    UncachedAuthor = Class.new(Author) do
+      # To confirm cache_key is set using updated_at and cache_key option passed to cache
+      undef_method :cache_key
+    end
+
+    Article = Class.new(::Model) do
+      # To confirm error is raised when cache_key is not set and cache_key option not passed to cache
+      undef_method :cache_key
+    end
+
+    ArticleSerializer = Class.new(ActiveModel::Serializer) do
+      cache only: [:place], skip_digest: true
+      attributes :title
+    end
+
     InheritedRoleSerializer = Class.new(RoleSerializer) do
       cache key: 'inherited_role', only: [:name, :special_attribute]
       attribute :special_attribute
@@ -81,15 +96,26 @@ def test_cache_key_definition
       assert_equal(nil, @comment_serializer.class._cache_key)
     end
 
-    def test_cache_key_interpolation_with_updated_at
-      render_object_with_cache(@author)
-      assert_equal(nil, cache_store.fetch(@author.cache_key))
-      assert_equal(@author_serializer.attributes.to_json, cache_store.fetch("#{@author_serializer.class._cache_key}/#{@author_serializer.object.id}-#{@author_serializer.object.updated_at.strftime("%Y%m%d%H%M%S%9N")}").to_json)
+
+    def test_error_is_raised_if_cache_key_is_not_defined_on_object_or_passed_as_cache_option
+      article = Article.new(title: 'Must Read')
+      assert_raises ActiveModel::Serializer::Adapter::CachedSerializer::UndefinedCacheKey do
+        render_object_with_cache(article)
+      end
+    end
+
+    def test_cache_key_interpolation_with_updated_at_when_cache_key_is_not_defined_on_object
+      uncached_author            = UncachedAuthor.new(name: 'Joao M. D. Moura')
+      uncached_author_serializer = AuthorSerializer.new(uncached_author)
+
+      render_object_with_cache(uncached_author)
+      key = cache_key_with_adapter("#{uncached_author_serializer.class._cache_key}/#{uncached_author_serializer.object.id}-#{uncached_author_serializer.object.updated_at.strftime("%Y%m%d%H%M%S%9N")}")
+      assert_equal(uncached_author_serializer.attributes.to_json, ActionController::Base.cache_store.fetch(key).to_json)
     end
 
     def test_default_cache_key_fallback
       render_object_with_cache(@comment)
-      assert_equal(@comment_serializer.attributes.to_json, cache_store.fetch(@comment.cache_key).to_json)
+      assert_equal(@comment_serializer.attributes.to_json, ActionController::Base.cache_store.fetch(cache_key_with_adapter(@comment.cache_key)).to_json)
     end
 
     def test_cache_options_definition
@@ -111,8 +137,8 @@ def test_associations_separately_cache
       Timecop.freeze(Time.current) do
         render_object_with_cache(@post)
 
-        assert_equal(@post_serializer.attributes, cache_store.fetch(@post.cache_key))
-        assert_equal(@comment_serializer.attributes, cache_store.fetch(@comment.cache_key))
+        assert_equal(@post_serializer.attributes, ActionController::Base.cache_store.fetch(cache_key_with_adapter(@post.cache_key)))
+        assert_equal(@comment_serializer.attributes, ActionController::Base.cache_store.fetch(cache_key_with_adapter(@comment.cache_key)))
       end
     end
 
@@ -122,8 +148,9 @@ def test_associations_cache_when_updated
         render_object_with_cache(@post)
 
         # Check if it cached the objects separately
-        assert_equal(@post_serializer.attributes,    cached_serialization(@post_serializer))
-        assert_equal(@comment_serializer.attributes, cached_serialization(@comment_serializer))
+        assert_equal(@post_serializer.attributes, ActionController::Base.cache_store.fetch(cache_key_with_adapter(@post.cache_key)))
+        assert_equal(@comment_serializer.attributes, ActionController::Base.cache_store.fetch(cache_key_with_adapter(@comment.cache_key)))
+
 
         # Simulating update on comments relationship with Post
         new_comment            = Comment.new(id: 2567, body: 'ZOMG A NEW COMMENT')
@@ -134,8 +161,8 @@ def test_associations_cache_when_updated
         render_object_with_cache(@post)
 
         # Check if the the new comment was cached
-        assert_equal(new_comment_serializer.attributes, cached_serialization(new_comment_serializer))
-        assert_equal(@post_serializer.attributes, cached_serialization(@post_serializer))
+        assert_equal(new_comment_serializer.attributes, ActionController::Base.cache_store.fetch(cache_key_with_adapter(new_comment.cache_key)))
+        assert_equal(@post_serializer.attributes, ActionController::Base.cache_store.fetch(cache_key_with_adapter(@post.cache_key)))
       end
     end
 
@@ -150,7 +177,7 @@ def test_fragment_fetch_with_virtual_associations
       hash = render_object_with_cache(@location)
 
       assert_equal(hash, expected_result)
-      assert_equal({ place: 'Nowhere' }, cache_store.fetch(@location.cache_key))
+      assert_equal({ place: 'Nowhere' }, ActionController::Base.cache_store.fetch(cache_key_with_adapter(@location.cache_key)))
     end
 
     def test_fragment_cache_with_inheritance
@@ -161,9 +188,14 @@ def test_fragment_cache_with_inheritance
       refute_includes(base.keys, :special_attribute)
     end
 
+    def test_uses_adapter_in_cache_key
+      render_object_with_cache(@post)
+      assert_equal(@post_serializer.attributes, ActionController::Base.cache_store.fetch("#{@post.cache_key}/#{adapter.class.to_s.demodulize.underscore}"))
+    end
+
     def test_uses_file_digest_in_cache_key
       render_object_with_cache(@blog)
-      assert_equal(@blog_serializer.attributes, cache_store.fetch(@blog.cache_key_with_digest))
+      assert_equal(@blog_serializer.attributes, ActionController::Base.cache_store.fetch("#{cache_key_with_adapter(@blog.cache_key)}/#{@blog.class::FILE_DIGEST}"))
     end
 
     def test_cache_digest_definition
@@ -254,7 +286,16 @@ def test_warn_on_serializer_not_defined_in_file
     private
 
     def render_object_with_cache(obj, options = {})
-      serializable(obj, options).serializable_hash
+      @serializable_resource = serializable(obj, options).serializable_hash
+      @serializable_resource.serializable_hash
+    end
+
+    def adapter
+      @serializable_resource.adapter
+    end
+
+    def cache_key_with_adapter(key)
+      "#{key}/#{adapter.name.underscore}"
     end
 
     def cache_store

test/fixtures/poro.rb

@@ -55,8 +55,8 @@ class ProfilePreviewSerializer < ActiveModel::Serializer
 Blog     = Class.new(Model) do
   FILE_DIGEST = Digest::MD5.hexdigest(File.open(__FILE__).read)
 
-  def cache_key_with_digest
-    "#{cache_key}/#{FILE_DIGEST}"
+  def digest
+    FILE_DIGEST
   end
 end
 Role     = Class.new(Model)