Making progress, I think…
I built a scratch application (new app in FB, new app in rails) with just a script/generate scaffold Welcome.
Commented out the Welcome.find in the controller, and added a show.fbml.erb to the views.
Removed public/index.html.
Updated routes.rb:
map.resources :welcome
map.root :welcome
Added config.action_controller.protect_from_forgery = false to config.environment.rb.
When I set the app to iframe, no problem: displays the default welcome/show.html.erb page in a frame.
When I set it to fbml, I get the old “no data” error.
I added a logging statement in each of the erb files to confirm which (if any) were getting served, and when I use iframe, it serves show.html.erb… when I use fbml, it serves show.fbml.erb. All as expected.
Except that no matter what I put in show.fbml.erb, I always get no data in FB.
When I hit http://localhost:3000/welcomes/1.fbml or http://ssh1.tunnlr.com:10803/welcomes/1.fbml, the results display just fine, so the app is clearly sending data back.
Is there a verbose mode for the tunnlr connection to see what is being returned when my app responds? Or something I could put in the rails app itself to show what’s being returned?