progress on implementing new deserializer -- just have some behavior differences with relationships

Author: NullVoxPopuli

lib/active_model_serializers/adapter/json_api/deserialization.rb

@@ -84,19 +84,46 @@ def parse!(document, options = {})
         def parse(document, options = {})
           # TODO: change to jsonapi-ralis to have default conversion to flat hashes
           result = JSONAPI::Rails::DeserializableResource.new(document, options: options).to_hash
-          result = transform_keys(result) if options[:key_transform]
+          result = apply_options(result, options)
           result
         rescue JSONAPI::Parser::InvalidDocument => e
           return {} unless block_given?
           yield e
         end
 
+        def apply_options(hash, options)
+          hash = transform_keys(hash, options) if options[:key_transform]
+          hash = hash.deep_symbolize_keys
+          hash = filter_fields(hash, options)
+          hash = rename_fields(hash, options)
+          hash
+        end
+
         # TODO: transform the keys after parsing
         # @api private
         def transform_keys(hash, options)
           transform = options[:key_transform] || :underscore
           CaseTransform.send(transform, hash)
         end
+
+        # executes only
+        # then except
+        def filter_fields(hash, options)
+          hash = hash.select { |k, v| options[:only].include?(k) } if options[:only]
+          hash = hash.select { |k, v| !options[:except].include?(k) } if options[:except]
+          hash
+        end
+
+        def rename_fields(hash, options)
+          return hash unless options[:keys]
+
+          keys = options[:keys]
+          hash.each_with_object({}) do |(k, v), h|
+            k = keys.fetch(k, k)
+            h[k] = v
+            h
+          end
+        end
       end
     end
   end