Make nested layout usage independed of the outer template's :layout v…

…alue. Allows using partials in layouts.

lib/sinatra/base.rb

@@ -467,7 +467,7 @@ def render(engine, data, options={}, locals={}, &block)
 
       # compile and render template
       layout_was      = @default_layout
-      @default_layout = false if layout
+      @default_layout = false
       template        = compile_template(engine, data, options, views)
       output          = template.render(self, locals, &block)
       @default_layout = layout_was

test/templates_test.rb

@@ -101,6 +101,15 @@ def with_default_layout
     assert_equal "<h1>String Layout!</h1>\n<content><h1>Hello From String</h1></content>", body
   end
 
+  it 'is possible to use partials in layouts' do
+    render_app do
+      settings.layout { "<%= erb 'foo' %><%= yield %>" }
+      erb 'bar'
+    end
+    assert ok?
+    assert_equal "foobar", body
+  end
+
   it 'loads templates from source file' do
     mock_app { enable :inline_templates }
     assert_equal "this is foo\n\n", @app.templates[:foo][0]