[PATCH] Fix ActiveRecord::Base#to_xml and Hash#from_xml for namespaced model classes in Ruby module

I meant to say... Replying to mbbx6spp:

I looked through 39 tickets *mentioning to_xml* looking for this to be reported already, but saw no mention of this defect for this particular edge case.

And while I am digging I will try to come up with a patch for this.

For those interested in the workaround for this:

contact = Legacy::Contact.find :first
xml = contact.to_xml(:root => 'legacy:contact')

For the collections case:

contacts = Legacy::Contact.find :all
xml = contact.to_xml(:root => 'legacy:contacts', :children => 'legacy:contact')

Hope this helps someone.

My code fix is not elegant, mostly because I didn't want to take too many liberties and add a helper instance method to String somewhere in activesupport to remove the direct gsub! invocation here.

I changed the local/method variable name because I generally dislike having a local/method variable named the same as the method it is in. But please change as per Rails Core coding style if patch is accepted.

Patch is:

Index: lib/active_record/xml_serialization.rb
===================================================================
--- lib/active_record/xml_serialization.rb      (revision 6703)
+++ lib/active_record/xml_serialization.rb      (working copy)
@@ -148,8 +148,9 @@
     end
 
     def root
-      root = (options[:root] || @record.class.to_s.underscore).to_s
-      dasherize? ? root.dasherize : root
+      root_name = (options[:root] || @record.class.to_s.underscore).to_s
+      root_name.gsub!(/\//, ':') # for models that are namespaced in Ruby module
+      dasherize? ? root_name.dasherize : root_name
     end
     
     def dasherize?

To help justify this fix: I forgot to mention that the current XML produced from to_xml for this namespaced model case is invalid XML. But adding this fix we automatically generate valid XML for this edge case.

This is only half of the solution. The other part of the solution is to modify the Hash conversion extensions in activesupport to make sure coming from the other way, the XML can be deserialized.

Unfortunately it past my bed time and don't work well after 11pm, so off to bed now. After work hours tomorrow I will revisit this.

See my ActiveRecord::Base#to_xml Woes blog posting for interim patch for this issue.

Test case and code fix for #8305

See #3808 for related ticket in ActiveRecord.

Replying to mbbx6spp:

See #3808 for related ticket in ActiveRecord.

That should have said #8308.

This seems to be a partial fix. There is still a problem when using :include in to_xml's options. Any included associations still show the mal-formed xml. The problem seems to be in ActiveRecord::XmlSerialzier's add_includes method which builds the tag name manually instead of leaving it up to the child record.

Sorry...1st time submitting a ticket...didn't mean to close it...

Just found something else. Nesting namespaces doesn't work well either. Let's say you have:

Legacy::Purchasing::Requisition and Legacy::ServicesProcurement::Requisition

Your patch creates the xml tags as: <legacy:purchasing:requisition> and <legacy:services_procurement:requisition>

The 2nd set of colons, again, results in mal-formed XML. Suggest using another method of depicting nested namespaces. Not an XML expert, so I won't presume to know what that might be.

Great! Thanks for the feedback to the patch. It has been sitting a little dormant and I needed a reminder of some kind.

Over the weekend I will try to add a patch based on a newer rails trunk revision and at a minimum add the tests demonstrating the two issues you mention above.

Sure would be nice to see this get fixed...I'm getting bit by it as well.

There is another edge case. In Camping, it uses ActiveRecord as well, all models live in YourApp::Models, which would end in double namespaces.

YourApp::Models::User would become your_app:models:user which isn't valid xml either. This may, of course, also happen in any Rails app, although it is less likely.

I don't know how to cope with that. Perhaps it would be better to not use namespaces but another character, probably the underscore. But then, the deserialization would be more difficult or even impossible.

I was personally thinking of using hyphen instead of underscore just for the delimiters of modules, but then use an XML namespace to delimit the module(s) from the class. For example, YourApp::Models::User would translate to your_app-models:user. This way there is always one XML namespace that translates to an ordered sequence of Ruby modules.

Am I missing something? If not, this would seem to allow deterministic serialization and deserialization.

I promise to crave out an hour this weekend to add at least the test cases to fail for the current code base and patch and then start with a better patch once I received some critique of the above scheme.

I meant "carve out" instead of "crave out" in the above message:)