Fix a crash in StringSplitter

Close https://github.com/haml/haml/issues/1096

Applying https://github.com/judofyr/temple/pull/138 to Haml's fork until
it's merged to upstream.

lib/haml/string_splitter.rb

@@ -46,6 +46,7 @@ module Haml
 
             case type
             when :on_tstring_content
+              beg_str, end_str = escape_quotes(beg_str, end_str)
               exps << [:static, eval("#{beg_str}#{str}#{end_str}").to_s]
             when :on_embexpr_beg
               embedded = shift_balanced_embexpr(tokens)
@@ -54,6 +55,16 @@ module Haml
           end
         end
 
+        # Some quotes are split-unsafe. Replace such quotes with null characters.
+        def escape_quotes(beg_str, end_str)
+          case [beg_str[-1], end_str]
+          when ['(', ')'], ['[', ']'], ['{', '}']
+            [beg_str.sub(/.\z/) { "\0" }, "\0"]
+          else
+            [beg_str, end_str]
+          end
+        end
+
         def shift_balanced_embexpr(tokens)
           String.new.tap do |embedded|
             embexpr_open = 1

test/haml/engine/old_attribute_test.rb

@@ -78,6 +78,15 @@ describe Haml::Engine do
       HAML
     end
 
+    it 'renders %() string attributes' do
+      assert_render(<<-'HTML'.unindent, <<-'HAML'.unindent)
+        <p title='foo(a)'></p>
+      HTML
+        - some_local_variable = 'a'
+        %p{ title: %(foo(#{some_local_variable})) }
+      HAML
+    end
+
     describe 'runtime attributes' do
       it 'renders runtime hash attribute' do
         assert_render(<<-HTML.unindent, <<-HAML.unindent)