[Haml] Fix a bug with elements with dynamic attributes and no content.

Closes gh-47

doc-src/HAML_CHANGELOG.md

@@ -3,6 +3,11 @@
 * Table of contents
 {:toc}
 
+## 2.2.10 (Unreleased)
+
+* Fixed a bug where elements with dynamic attributes and no content
+  would have too much whitespace between the opening and closing tag.
+
 ## [2.2.9](http://github.com/nex3/haml/commit/2.2.9)
 
 * Fixed a bug where Haml's text was concatenated to the wrong buffer

lib/haml/precompiler.rb

@@ -727,6 +727,7 @@ END
       raise SyntaxError.new("Self-closing tags can't have content.", last_line - 1) if self_closing && !value.empty?
 
       self_closing ||= !!( !block_opened? && value.empty? && @options[:autoclose].include?(tag_name) )
+      value = nil if value.empty? && (block_opened? || self_closing)
 
       dont_indent_next_line =
         (nuke_outer_whitespace && !block_opened?) ||
@@ -751,7 +752,7 @@ END
         return if tag_closed
       else
         flush_merged_text
-        content = value.empty? || parse ? 'nil' : value.dump
+        content = parse ? 'nil' : value.inspect
         if attributes_hashes.empty?
           attributes_hashes = ''
         elsif attributes_hashes.size == 1
@@ -769,7 +770,7 @@ END
 
       return if self_closing
 
-      if value.empty?
+      if value.nil?
         push_and_tabulate([:element, [tag_name, nuke_outer_whitespace, nuke_inner_whitespace]])
         @output_tabs += 1 unless nuke_inner_whitespace
         return

test/haml/engine_test.rb

@@ -123,6 +123,17 @@ class EngineTest < Test::Unit::TestCase
     assert_equal("<p class='3'>foo</p>", render("%p{:class => 1+2} foo").chomp)
   end
 
+  def test_dynamic_attributes_with_no_content
+    assert_equal(<<HTML, render(<<HAML))
+<p>
+  <a href='http://haml-lang.com'></a>
+</p>
+HTML
+%p
+  %a{:href => "http://" + "haml-lang.com"}
+HAML
+  end
+
   def test_nil_should_render_empty_tag
     assert_equal("<div class='no_attributes'></div>",
                  render(".no_attributes{:nil => nil}").chomp)