validates_presence_of :link in a model breaks the ability to do Model.create in migrations

That's what validations do, they keep you from entering bad data. You can try out toolmantim's handy tip on safely using models in migrations at http://rails.techno-weenie.net/tip/2006/2/23/safely_using_models_in_migrations, however.

I have the same problem. The name "link" makes it break. Same exception here. Apparently, if a model has "link" as attribute and validates it, in migrations some link method of rake gets called.

example:

class Item < ActiveRecord::Base

validates_presence_of :link

end

in migration:

Item.new :link => "http://slashdot.org" p item.attributes {"link"=>"http://slashdot.org/"} item.save!

... Bang, the exception above

removing the validates_presence_of :link in Item makes it work - the Item is save correctly.

This is an issue with Rake, they include FileUtils into Object so it's easy to do file operations in a Rake task. One of these methods is link. Because they're included in Object, they are also present in ActiveRecord. The validation tries to call the method link on the ActiveRecord instance and finds the link from FileUtils. That's why this is going wrong.

Test with Object.new.send(:link).

I'm afraid we can't fix this in Rails, you're going to have to go upstream to Rake and work out a solution for this.