Ticket #6544: django-allow-comments-before-extends.diff

django/template/__init__.py

@@ -303 +303 @@
         return NodeList()
 
     def extend_nodelist(self, nodelist, node, token):
-        if node.must_be_first and nodelist:
-            try:
-                if nodelist.contains_nontext:
-                    raise AttributeError
-            except AttributeError:
-                raise TemplateSyntaxError("%r must be the first tag in the template." % node)
+        if node.must_be_first and nodelist_extends_filter(nodelist):
+            raise TemplateSyntaxError("%r must be the first tag in the template (preceding nodes: %s)" % (node, nodelist))
         if isinstance(nodelist, NodeList) and not isinstance(node, TextNode):
             nodelist.contains_nontext = True
         nodelist.append(node)
@@ -360 +356 @@
         else:
             raise TemplateSyntaxError("Invalid filter: '%s'" % filter_name)
 
+
+is_whitespace = re.compile(r"^\s+$").search
+def nodelist_extends_filter (nodelist):
+    """Filter ignorable nodes preceding a "extends" tag."""
+    return filter(lambda x: not node_extends_ignore(x), nodelist)
+
+
+def node_extends_ignore (node):
+    """Determine if the contents of the node can be ignored preceding
+    a "extends" tag."""
+    from defaulttags import CommentNode
+    return (isinstance(node, TextNode) and is_whitespace(node.s)) or \
+           isinstance(node, CommentNode)
+
+
 class TokenParser(object):
     """
     Subclass this and implement the top() method to parse a template line. When