Fixed an html5lib tree builder crash which happened when html5lib

moved a tag with a multivalued attribute from one part of the tree to
another. [bug=1019603]

3 files changed, 24 insertions, 1 deletions

diff --git a/NEWS.txt b/NEWS.txt
index 0443968..2ca93ce 100644
--- a/NEWS.txt
+++ b/NEWS.txt
@@ -1,3 +1,9 @@
+= 4.1.1 (Unreleased) =
+
+Fixed an html5lib tree builder crash which happened when html5lib
+moved a tag with a multivalued attribute from one part of the tree to
+another. [bug=1019603]
+
 = 4.1.0 (20120529) =
 
 * Added experimental support for fixing Windows-1252 characters
diff --git a/bs4/builder/__init__.py b/bs4/builder/__init__.py
index 4c22b86..dc7deb9 100644
--- a/bs4/builder/__init__.py
+++ b/bs4/builder/__init__.py
@@ -157,7 +157,16 @@ class TreeBuilder(object):
                     # value is a whitespace-separated list of CSS
                     # classes. Split it into a list.
                     value = attrs[cdata_list_attr]
-                    values = whitespace_re.split(value)
+                    if isinstance(value, basestring):
+                        values = whitespace_re.split(value)
+                    else:
+                        # html5lib sometimes calls setAttributes twice
+                        # for the same tag when rearranging the parse
+                        # tree. On the second call the attribute value
+                        # here is already a list.  If this happens,
+                        # leave the value alone rather than trying to
+                        # split it again.
+                        values = value
                     attrs[cdata_list_attr] = values
         return attrs
 
diff --git a/bs4/testing.py b/bs4/testing.py
index 5a84b0b..51f7e22 100644
--- a/bs4/testing.py
+++ b/bs4/testing.py
@@ -202,6 +202,14 @@ class HTMLTreeBuilderSmokeTest(object):
             "<tbody><tr><td>Bar</td></tr></tbody>"
             "<tfoot><tr><td>Baz</td></tr></tfoot></table>")
 
+    def test_deeply_nested_multivalued_attribute(self):
+        # html5lib can set the attributes of the same tag many times
+        # as it rearranges the tree. This has caused problems with
+        # multivalued attributes.
+        markup = '<table><div><div class="css"></div></div></table>'
+        soup = self.soup(markup)
+        self.assertEqual(["css"], soup.div.div['class'])
+
     def test_angle_brackets_in_attribute_values_are_escaped(self):
         self.assertSoupEquals('<a b="<a>"></a>', '<a b="&lt;a&gt;"></a>')