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.

2 files changed, 26 insertions, 6 deletions

diff --git a/actionpack/test/template/erb/tag_helper_test.rb b/actionpack/test/template/erb/tag_helper_test.rb
index cc96a43901..b5b7ae87de 100644
--- a/actionpack/test/template/erb/tag_helper_test.rb
+++ b/actionpack/test/template/erb/tag_helper_test.rb
@@ -20,7 +20,7 @@ module ERBTest
   end
 
   class DeprecatedViewContext < ViewContext
-    include ActionView::Helpers::DeprecatedBlockHelpers
+    # include ActionView::Helpers::DeprecatedBlockHelpers
   end
 
   module SharedTagHelpers
@@ -31,28 +31,36 @@ module ERBTest
       ActionView::Template::Handlers::Erubis.new(template).evaluate(context.new)
     end
 
+    def maybe_deprecated
+      if @deprecated
+        assert_deprecated { yield }
+      else
+        yield
+      end
+    end
+
     test "percent equals works for content_tag and does not require parenthesis on method call" do
-      assert_equal "<div>Hello world</div>", render_content("content_tag :div", "Hello world")
+      maybe_deprecated { assert_equal "<div>Hello world</div>", render_content("content_tag :div", "Hello world") }
     end
 
     test "percent equals works for javascript_tag" do
       expected_output = "<script type=\"text/javascript\">\n//<![CDATA[\nalert('Hello')\n//]]>\n</script>"
-      assert_equal expected_output, render_content("javascript_tag", "alert('Hello')")
+      maybe_deprecated { assert_equal expected_output, render_content("javascript_tag", "alert('Hello')") }
     end
 
     test "percent equals works for javascript_tag with options" do
       expected_output = "<script id=\"the_js_tag\" type=\"text/javascript\">\n//<![CDATA[\nalert('Hello')\n//]]>\n</script>"
-      assert_equal expected_output, render_content("javascript_tag(:id => 'the_js_tag')", "alert('Hello')")
+      maybe_deprecated { assert_equal expected_output, render_content("javascript_tag(:id => 'the_js_tag')", "alert('Hello')") }
     end
 
     test "percent equals works with form tags" do
       expected_output = "<form action=\"foo\" method=\"post\">hello</form>"
-      assert_equal expected_output, render_content("form_tag('foo')", "<%= 'hello' %>")
+      maybe_deprecated { assert_equal expected_output, render_content("form_tag('foo')", "<%= 'hello' %>") }
     end
 
     test "percent equals works with fieldset tags" do
       expected_output = "<fieldset><legend>foo</legend>hello</fieldset>"
-      assert_equal expected_output, render_content("field_set_tag('foo')", "<%= 'hello' %>")
+      maybe_deprecated { assert_equal expected_output, render_content("field_set_tag('foo')", "<%= 'hello' %>") }
     end
   end
 
@@ -77,6 +85,10 @@ module ERBTest
       "<% __in_erb_template=true %><% #{str} do %>#{rest}<% end %>"
     end
 
+    def setup
+      @deprecated = true
+    end
+
     include SharedTagHelpers
   end
 end
\ No newline at end of file
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")