Run :erb filter in the template context

Close #1113

lib/haml/filters/erb.rb

@@ -3,7 +3,7 @@ module Haml
   class Filters
     class Erb < TiltBase
       def compile(node)
-        compile_with_tilt(node, 'erb')
+        precompiled_with_tilt(node, 'erb')
       end
     end
   end

lib/haml/filters/tilt_base.rb

@@ -21,6 +21,12 @@ def explicit_require?(needed_registration)
 
       private
 
+      # TODO: support interpolation
+      def precompiled_with_tilt(node, name)
+        src = ::Tilt["t.#{name}"].new { node.value[:text] }.send(:precompiled, {}).first
+        [:dynamic, src]
+      end
+
       def compile_with_tilt(node, name, indent_width: 0)
         if ::Haml::Util.contains_interpolation?(node.value[:text])
           dynamic_compile(node, name, indent_width: indent_width)

test/haml/filters_test.rb

@@ -126,11 +126,10 @@ class ErbFilterTest < Haml::TestCase
     assert_haml_ugly(%Q{:erb\n  <%= "foo" +\n      "bar" +\n      "baz" %>})
   end
 
-  test "should evaluate in the same context as Haml" do; skip
-    haml  = ":erb\n  <%= foo %>"
-    html  = "bar\n"
-    scope = Object.new.instance_eval {foo = "bar"; nil if foo; binding}
-    assert_equal(html, render(haml, :scope => scope))
+  test "should evaluate in the same context as Haml" do
+    haml  = "- foo = 'bar'\n:erb\n  <%= foo %>"
+    html  = "bar\n\n"
+    assert_equal(html, render(haml))
   end
 
   test "should use Rails's XSS safety features" do; skip