Fix very strange bug with form_for and capture_html (double render)

padrino-helpers/lib/padrino-helpers/form_helpers.rb

@@ -31,7 +31,8 @@ module FormHelpers
       # @api public
       def form_for(object, url, settings={}, &block)
         instance = builder_instance(object, settings)
-        form_tag(url, settings) { capture_html(instance, &block) }
+        html = capture_html(instance, &block)
+        form_tag(url, settings) { html }
       end
 
       ##

padrino-helpers/lib/padrino-helpers/output_helpers.rb

@@ -48,12 +48,12 @@ def render(engine, *) # @private
       # @api semipublic
       def capture_html(*args, &block)
         handler = find_proper_handler
-        captured_html = ""
+        captured_block, captured_html = nil, ""
         if handler && handler.is_type? && handler.block_is_type?(block)
-          captured_html = handler.capture_from_template(*args, &block)
+          captured_html, captured_block = handler.capture_from_template(*args, &block)
         end
         # invoking the block directly if there was no template
-        captured_html = block_given? && block.call(*args) if captured_html.blank?
+        captured_html = block_given? && ( captured_block || block.call(*args) )  if captured_html.blank?
         captured_html
       end
       alias :capture :capture_html

padrino-helpers/lib/padrino-helpers/output_helpers/slim_handler.rb

@@ -31,10 +31,10 @@ def is_type?
         #
         def capture_from_template(*args, &block)
           self.output_buffer, _buf_was = ActiveSupport::SafeBuffer.new, self.output_buffer
-          block.call(*args)
+          captured_block = block.call(*args)
           ret = eval("@_out_buf", block.binding)
           self.output_buffer = _buf_was
-          ret
+          [ ret, captured_block ]
         end
 
         ##

padrino-helpers/test/fixtures/render_app/app.rb

@@ -31,6 +31,10 @@ class RenderDemo < Padrino::Application
     render :explicit_engine
   end
 
+  get '/double_capture_:ext' do
+    render "double_capture_#{params[:ext]}"
+  end
+
   # partial with object
   get '/partial/object' do
     partial 'template/user', :object => RenderUser.new('John'), :locals => { :extra => "bar" }

padrino-helpers/test/fixtures/render_app/views/double_capture_erb.erb

@@ -0,0 +1,3 @@
+<% form_for( :object, '/' ) do |f| %>
+  <%= $number_of_captures += 1 %>
+<% end %>

padrino-helpers/test/fixtures/render_app/views/double_capture_haml.haml

@@ -0,0 +1,2 @@
+- form_for :object, '/' do |f|
+  = $number_of_captures += 1

padrino-helpers/test/fixtures/render_app/views/double_capture_slim.slim

@@ -0,0 +1,2 @@
+- form_for :object, '/' do |f|
+  = $number_of_captures += 1

padrino-helpers/test/test_render_helpers.rb

@@ -72,5 +72,23 @@ def app
       assert_have_selector 'p.slim span',  :content => "slim"
       assert_have_selector 'p.end',   :content => "haml"
     end
+
+    should "capture slim template once and only once" do
+      $number_of_captures = 0
+      visit '/double_capture_slim'
+      assert_equal 1,$number_of_captures
+    end
+
+    should "capture haml template once and only once" do
+      $number_of_captures = 0
+      visit '/double_capture_haml'
+      assert_equal 1,$number_of_captures
+    end
+
+    should "capture erb template once and only once" do
+      $number_of_captures = 0
+      visit '/double_capture_erb'
+      assert_equal 1,$number_of_captures
+    end
   end
 end