From 9de83050d3a4b260d4aeb5d09ec4eb64f913ba64 Mon Sep 17 00:00:00 2001
From: Carlhuda <carlhuda@engineyard.com>
Date: Mon, 15 Mar 2010 11:58:05 -0700
Subject: 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.
---
 actionpack/lib/action_view/template/handlers/erb.rb | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

(limited to 'actionpack/lib/action_view/template')

diff --git a/actionpack/lib/action_view/template/handlers/erb.rb b/actionpack/lib/action_view/template/handlers/erb.rb
index ac5902cc0e..705c2bf82e 100644
--- a/actionpack/lib/action_view/template/handlers/erb.rb
+++ b/actionpack/lib/action_view/template/handlers/erb.rb
@@ -8,6 +8,13 @@ module ActionView
       super(value.to_s)
     end
     alias :append= :<<
+
+    def append_if_string=(value)
+      if value.is_a?(String) && !value.is_a?(NonConcattingString)
+        ActiveSupport::Deprecation.warn("<% %> style block helpers are deprecated. Please use <%= %>", caller)
+        self << value
+      end
+    end
   end
 
   module Template::Handlers
@@ -21,14 +28,24 @@ module ActionView
         src << "@output_buffer.safe_concat('" << escape_text(text) << "');"
       end
 
+      BLOCK_EXPR = /(do|\{)(\s*\|[^|]*\|)?\s*\Z/
+
       def add_expr_literal(src, code)
-        if code =~ /(do|\{)(\s*\|[^|]*\|)?\s*\Z/
+        if code =~ BLOCK_EXPR
           src << '@output_buffer.append= ' << code
         else
           src << '@output_buffer.append= (' << code << ');'
         end
       end
 
+      def add_stmt(src, code)
+        if code =~ BLOCK_EXPR
+          src << '@output_buffer.append_if_string= ' << code
+        else
+          super
+        end
+      end
+
       def add_expr_escaped(src, code)
         src << '@output_buffer.append= ' << escaped_expr(code) << ';'
       end
-- 
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