[Haml] Fix an odd outer-whitespace-nuking bug.

doc-src/HAML_CHANGELOG.md

@@ -9,6 +9,9 @@
   if passed a non-string value.
   Note that this doesn't affect any HTML escaping when XSS protection is disabled.
 
+* Fixed a bug in outer-whitespace nuking where whitespace-only Ruby strings
+  blocked whitespace nuking beyond them.
+
 ## [2.2.10](http://github.com/nex3/haml/commit/2.2.10)
 
 * Fixed a bug where elements with dynamic attributes and no content

lib/haml/precompiler.rb

@@ -1005,23 +1005,24 @@ END
 
     # Get rid of and whitespace at the end of the buffer
     # or the merged text
-    def rstrip_buffer!
-      if @to_merge.empty?
+    def rstrip_buffer!(index = -1)
+      last = @to_merge[index]
+      if last.nil?
         push_silent("_hamlout.rstrip!", false)
         @dont_tab_up_next_text = true
         return
       end
 
-      last = @to_merge.last
       case last.first
       when :text
         last[1].rstrip!
         if last[1].empty?
-          @to_merge.pop
-          rstrip_buffer!
+          @to_merge.slice! index
+          rstrip_buffer! index
         end
       when :script
         last[1].gsub!(/\(haml_temp, (.*?)\);$/, '(haml_temp.rstrip, \1);')
+        rstrip_buffer! index - 1
       else
         raise SyntaxError.new("[HAML BUG] Undefined entry in Haml::Precompiler@to_merge.")
       end

test/haml/engine_test.rb

@@ -321,6 +321,18 @@ HTML
 HAML
   end
 
+  def test_outer_whitespace_nuke_with_empty_script
+    assert_equal(<<HTML, render(<<HAML))
+<p>
+  foo<a></a></p>
+HTML
+%p
+  foo
+  = "  "
+  %a>
+HAML
+  end
+
   def test_both_case_indentation_work_with_deeply_nested_code
     result = <<RESULT
 <h2>