[Haml] Allow - if with no content to be followed by - else with content.

Closes gh-62

doc-src/HAML_CHANGELOG.md

@@ -3,6 +3,15 @@
 * Table of contents
 {:toc}
 
+## 2.2.15 (Unreleased)
+
+* Allow `if` statements with no content followed by `else` clauses.
+  For example:
+
+    - if foo
+    - else
+      bar
+
 ## [2.2.14](http://github.com/nex3/haml/commit/2.2.14)
 
 * Don't print warnings when escaping attributes containing non-ASCII characters

lib/haml/precompiler.rb

@@ -246,7 +246,13 @@ END
         # It's important to preserve tabulation modification for keywords
         # that involve choosing between posible blocks of code.
         if %w[else elsif when].include?(keyword)
-          @dont_indent_next_line, @dont_tab_up_next_text = @to_close_stack.last[1..2]
+          # @to_close_stack may not have a :script on top
+          # when the preceding "- if" has nothing nested
+          if @to_close_stack.last && @to_close_stack.last.first == :script
+            @dont_indent_next_line, @dont_tab_up_next_text = @to_close_stack.last[1..2]
+          else
+            push_and_tabulate([:script, @dont_indent_next_line, @dont_tab_up_next_text])
+          end
 
           # when is unusual in that either it will be indented twice,
           # or the case won't have created its own indentation

test/haml/engine_test.rb

@@ -581,6 +581,16 @@ HTML
 HAML
   end
 
+  def test_if_without_content_and_else
+    assert_equal(<<HTML, render(<<HAML))
+foo
+HTML
+- if false
+- else
+  foo
+HAML
+  end
+
   # HTML escaping tests
 
   def test_ampersand_equals_should_escape