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.

1 files changed, 8 insertions, 0 deletions

diff --git a/actionpack/test/template/render_test.rb b/actionpack/test/template/render_test.rb
index cea8ab1bce..e66202e8fe 100644
--- a/actionpack/test/template/render_test.rb
+++ b/actionpack/test/template/render_test.rb
@@ -228,6 +228,14 @@ module RenderTestCases
       @view.render(:file => "test/hello_world.erb", :layout => "layouts/yield")
   end
 
+  # TODO: Move to deprecated_tests.rb
+  def test_render_with_nested_layout_deprecated
+    assert_deprecated do
+      assert_equal %(<title>title</title>\n\n\n<div id="column">column</div>\n<div id="content">content</div>\n),
+        @view.render(:file => "test/deprecated_nested_layout.erb", :layout => "layouts/yield")
+    end
+  end
+
   def test_render_with_nested_layout
     assert_equal %(<title>title</title>\n\n\n<div id="column">column</div>\n<div id="content">content</div>\n),
       @view.render(:file => "test/nested_layout.erb", :layout => "layouts/yield")