Allow pagination for nested resources but not for included resources

lib/jsonapi/active_relation_resource_finder.rb

@@ -110,13 +110,13 @@ def find_fragments(filters, options = {})
       # @return [Hash{ResourceIdentity => {identity: => ResourceIdentity, cache: cache_field, attributes: => {name => value}, related: {relationship_name: [] }}}]
       #    the ResourceInstances matching the filters, sorting, and pagination rules along with any request
       #    additional_field values
-      def find_related_fragments(source_rids, relationship_name, options = {})
+      def find_related_fragments(source_rids, relationship_name, options = {}, included_key = nil)
         relationship = _relationship(relationship_name)
 
         if relationship.polymorphic? && relationship.foreign_key_on == :self
           find_related_polymorphic_fragments(source_rids, relationship, options)
         else
-          find_related_monomorphic_fragments(source_rids, relationship, options)
+          find_related_monomorphic_fragments(source_rids, relationship, included_key, options)
         end
       end
 
@@ -162,7 +162,7 @@ def find_records_by_keys(keys, options = {})
         records.where({ _primary_key => keys })
       end
 
-      def find_related_monomorphic_fragments(source_rids, relationship, options = {})
+      def find_related_monomorphic_fragments(source_rids, relationship, included_key, options = {})
         source_ids = source_rids.collect {|rid| rid.id}
 
         context = options[:context]
@@ -185,7 +185,8 @@ def find_related_monomorphic_fragments(source_rids, relationship, options = {})
 
         # ToDO: Remove count check. Currently pagination isn't working with multiple source_rids (i.e. it only works
         # for show relationships, not related includes).
-        if paginator && source_rids.count == 1
+        # Check included_key to not paginate included resources but ensure that nested resources can be paginated
+        if paginator && source_rids.count == 1 && !included_key
           records = related_klass.apply_pagination(records, paginator, order_options)
         end
 

lib/jsonapi/processor.rb

@@ -469,7 +469,9 @@ def get_related(resource_klass, source_resources, include_related, options)
         find_related_resource_options[:sort_criteria] = relationship.resource_klass.default_sort
         find_related_resource_options[:cache] = resource_klass.caching?
 
-        related_identities = resource_klass.find_related_fragments(source_rids, relationship_name, find_related_resource_options)
+        related_identities = resource_klass.find_related_fragments(
+          source_rids, relationship_name, find_related_resource_options, key
+        )
 
         related_identities.each_pair do |identity, v|
           related[relationship_name][:resources][identity] =

test/unit/resource/active_relation_resource_finder_test.rb

@@ -121,6 +121,36 @@ def test_find_related_has_many_fragments_no_attributes
     assert_equal 2, related_identities[JSONAPI::ResourceIdentity.new(TagResource, 502)][:related][:tags].length
   end
 
+  def test_find_related_has_many_fragments_pagination
+    params = ActionController::Parameters.new(number: 2, size: 4)
+    options = { paginator: PagedPaginator.new(params) }
+    source_rids = [JSONAPI::ResourceIdentity.new(ARPostResource, 15)]
+
+    related_identities = ARPostResource.find_related_fragments(source_rids, 'tags', options)
+
+    assert_equal 1, related_identities.length
+    assert_equal JSONAPI::ResourceIdentity.new(TagResource, 516), related_identities.keys[0]
+    assert_equal JSONAPI::ResourceIdentity.new(TagResource, 516), related_identities.values[0][:identity]
+    assert related_identities.values[0].is_a?(Hash)
+    assert_equal 2, related_identities.values[0].length
+    assert_equal 1, related_identities.values[0][:related][:tags].length
+  end
+
+  def test_find_related_has_many_fragments_pagination_included_key
+    params = ActionController::Parameters.new(number: 2, size: 4)
+    options = { paginator: PagedPaginator.new(params) }
+    source_rids = [JSONAPI::ResourceIdentity.new(ARPostResource, 15)]
+
+    related_identities = ARPostResource.find_related_fragments(source_rids, 'tags', options, :tags)
+
+    assert_equal 5, related_identities.length
+    assert_equal JSONAPI::ResourceIdentity.new(TagResource, 502), related_identities.keys[0]
+    assert_equal JSONAPI::ResourceIdentity.new(TagResource, 502), related_identities.values[0][:identity]
+    assert related_identities.values[0].is_a?(Hash)
+    assert_equal 2, related_identities.values[0].length
+    assert_equal 1, related_identities.values[0][:related][:tags].length
+  end
+
   def test_find_related_has_many_fragments_cache_field
     options = { cache: true }
     source_rids = [JSONAPI::ResourceIdentity.new(ARPostResource, 1),
@@ -200,7 +230,7 @@ def test_find_related_polymorphic_fragments_cache_field
   end
 
   def test_find_related_polymorphic_fragments_cache_field_attributes
-    options = { cache: true , attributes: [:name] }
+    options = { cache: true, attributes: [:name] }
     source_rids = [JSONAPI::ResourceIdentity.new(PictureResource, 1),
                    JSONAPI::ResourceIdentity.new(PictureResource, 2),
                    JSONAPI::ResourceIdentity.new(PictureResource, 20)]