Fix fragment caching inherited serializers to use distinct per-serializer caches.

Author: Logan Serman

CHANGELOG.md

@@ -26,6 +26,7 @@ Features:
 - [#1340](https://github.com/rails-api/active_model_serializers/pull/1340) Add support for resource-level meta. (@beauby)
 
 Fixes:
+- [#1622](https://github.com/rails-api/active_model_serializers/pull/1622) Fix fragment caching inherited serializers to use distinct per-serializer caches. (@lserman)
 - [#1478](https://github.com/rails-api/active_model_serializers/pull/1478) Cache store will now be correctly set when serializers are
   loaded *before* Rails initializes. (@bf4)
 - [#1570](https://github.com/rails-api/active_model_serializers/pull/1570) Fixed pagination issue with last page size. (@bmorrall)

lib/active_model_serializers/fragment_cache.rb

@@ -15,7 +15,7 @@ def fetch
       object = serializer.object
 
       # It will split the serializer into two, one that will be cached and one that will not
-      serializers = fragment_serializer(object.class.name)
+      serializers = fragment_serializer
 
       # Get serializable hash from both
       cached_hash     = serialize(object, serializers[:cached])
@@ -79,10 +79,12 @@ def add_attributes_to_serializer(serializer, attributes, attributes_keys)
     #     User_AdminCachedSerializer
     #     User_AdminNonCachedSerializer
     #
-    def fragment_serializer(name)
-      klass      = serializer.class
-      cached     = "#{to_valid_const_name(name)}CachedSerializer"
-      non_cached = "#{to_valid_const_name(name)}NonCachedSerializer"
+    def fragment_serializer
+      klass                 = serializer.class
+      serializer_class_name = to_valid_const_name(klass.name)
+
+      cached     = "Cached#{serializer_class_name}"
+      non_cached = "NonCached#{serializer_class_name}"
 
       cached_serializer     = get_or_create_serializer(cached)
       non_cached_serializer = get_or_create_serializer(non_cached)

test/cache_test.rb

@@ -1,6 +1,12 @@
 require 'test_helper'
 require 'tmpdir'
 require 'tempfile'
+
+InheritedRoleSerializer = Class.new(RoleSerializer) do
+  cache key: 'inherited_role', only: [:name, :special_attribute]
+  attribute :special_attribute
+end
+
 module ActiveModelSerializers
   class CacheTest < ActiveSupport::TestCase
     def setup
@@ -150,6 +156,14 @@ def test_fragment_fetch_with_virtual_associations
       assert_equal({ place: 'Nowhere' }, ActionController::Base.cache_store.fetch(@location.cache_key))
     end
 
+    def test_fragment_cache_with_inheritance
+      inherited = render_object_with_cache(@role, serializer: InheritedRoleSerializer)
+      base = render_object_with_cache(@role)
+
+      assert_includes(inherited.keys, :special_attribute)
+      refute_includes(base.keys, :special_attribute)
+    end
+
     def test_uses_file_digest_in_cache_key
       render_object_with_cache(@blog)
       assert_equal(@blog_serializer.attributes, ActionController::Base.cache_store.fetch(@blog.cache_key_with_digest))
@@ -242,8 +256,8 @@ def test_warn_on_serializer_not_defined_in_file
 
     private
 
-    def render_object_with_cache(obj)
-      ActiveModel::SerializableResource.new(obj).serializable_hash
+    def render_object_with_cache(obj, options = {})
+      ActiveModel::SerializableResource.new(obj, options).serializable_hash
     end
   end
 end