Rails Ruby on Rails

Add deprecation notices for <% %>.

• The approach is to compile <% %> into a method call that checks whether the value returned from a block is a String. If it is, it concats to the buffer and prints a deprecation warning.
• <%= %> uses exactly the same logic to compile the template, which first checks to see whether it's compiling a block.
• This should have no impact on other uses of block in templates. For instance, in <% [1,2,3].each do |i| %><%= i %><% end %>, the call to each returns an Array, not a String, so the result is not concatenated
• In two cases (#capture and #cache), a String can be returned that should never be concatenated. We have temporarily created a String subclass called NonConcattingString which behaves (and is serialized) identically to String, but is not concatenated by the code that handles deprecated <% %> block helpers. Once we remove support for <% %> block helpers, we can remove NonConcattingString. http://github.com/rails/rails/commit/9de83050d3a4b260d4aeb5d09ec4eb...