DOI serializer.

app/serializers/datacite_doi_serializer.rb

@@ -119,19 +119,22 @@ class DataciteDoiSerializer
   attribute :doi, &:uid
 
   attribute :publisher do |object, params|
-    # publisher accessor will now always return a publisher object.
-    # new obj format only if ?publisher=true, otherwise serialize the old format (a string
-    if params && (params[:publisher] == "true")
-      if object.publisher.respond_to?(:to_hash)
-        object.publisher
-      elsif object.publisher.respond_to?(:to_str)
-        { "name" => object.publisher }
-      end
+    # new - format obj only if ?publisher=true, otherwise serialize the old format (a string)
+    if object.publisher.nil?
+      nil
     else
-      if object.publisher.respond_to?(:to_hash)
-        object.publisher["name"]
-      elsif object.publisher.respond_to?(:to_str)
-        object.publisher
+      if params&.dig(:publisher) == "true"
+        if object.publisher.respond_to?(:to_str)
+          { "name" => object.publisher }
+        else
+          object.publisher
+        end
+      else
+        if object.publisher.respond_to?(:to_str)
+          object.publisher
+        else
+          object.publisher["name"]
+        end
       end
     end
   end