from collections import deque

from antimarkdown import nodes


def render(*domtrees):
    if not domtrees:
        return u''

    root = nodes.Root()
    for dom in domtrees:
        build_render_tree(root, dom)
    lines = unicode(root).rstrip().splitlines()

    # Strip leading empty lines
    while not lines[0].strip():
        lines.pop(0)

    return nodes.normalize(u'\n'.join(lines))


def build_render_tree(root, domtree):
    """Process an ElementTree domtree and build a render tree.
    """
    opened = set()
    stack = deque([domtree])
    blackboard = {}
    render_tree = root
    current_node = render_tree

    while stack:
        domtree = stack.pop()

        if domtree not in opened:
            # Open the domtree

            # Build the render node.
            node_class = getattr(nodes, domtree.tag.upper(), nodes.Node)
            current_node = node_class(current_node, domtree, blackboard)

            stack.append(domtree)

            # Queue children
            for el in reversed(domtree):
                stack.append(el)

            opened.add(domtree)
        else:
            # Close the domtree
            current_node = current_node.parent

    return root

from collections import deque

from antimarkdown import nodes


def render(*domtrees):
    if not domtrees:
        return u''

    root = nodes.Root()
    for dom in domtrees:
        build_render_tree(root, dom)
    lines = unicode(root).rstrip().splitlines()

    # Strip leading empty lines
    while lines and not lines[0].strip():
        lines.pop(0)

    return nodes.normalize(u'\n'.join(lines))


def build_render_tree(root, domtree):
    """Process an ElementTree domtree and build a render tree.
    """
    opened = set()
    stack = deque([domtree])
    blackboard = {}
    render_tree = root
    current_node = render_tree

    while stack:
        domtree = stack.pop()

        if domtree not in opened:
            # Open the domtree

            # Build the render node.
            node_class = getattr(nodes, domtree.tag.upper(), nodes.Node)
            current_node = node_class(current_node, domtree, blackboard)

            stack.append(domtree)

            # Queue children
            for el in reversed(domtree):
                stack.append(el)

            opened.add(domtree)
        else:
            # Close the domtree
            current_node = current_node.parent

    return root

Handle case with empty block
Handle case with empty block

  from collections import deque
  
  from antimarkdown import nodes
  
  
  def render(*domtrees):
      if not domtrees:
          return u''
  
      root = nodes.Root()
      for dom in domtrees:
          build_render_tree(root, dom)
      lines = unicode(root).rstrip().splitlines()
  
      # Strip leading empty lines
-     while not lines[0].strip():
+     while lines and not lines[0].strip():
          lines.pop(0)
  
      return nodes.normalize(u'\n'.join(lines))
  
  
  def build_render_tree(root, domtree):
      """Process an ElementTree domtree and build a render tree.
      """
      opened = set()
      stack = deque([domtree])
      blackboard = {}
      render_tree = root
      current_node = render_tree
  
      while stack:
          domtree = stack.pop()
  
          if domtree not in opened:
              # Open the domtree
  
              # Build the render node.
              node_class = getattr(nodes, domtree.tag.upper(), nodes.Node)
              current_node = node_class(current_node, domtree, blackboard)
  
              stack.append(domtree)
  
              # Queue children
              for el in reversed(domtree):
                  stack.append(el)
  
              opened.add(domtree)
          else:
              # Close the domtree
              current_node = current_node.parent
  
      return root
  
Handle case with empty block
## Code Before:
from collections import deque

from antimarkdown import nodes


def render(*domtrees):
    if not domtrees:
        return u''

    root = nodes.Root()
    for dom in domtrees:
        build_render_tree(root, dom)
    lines = unicode(root).rstrip().splitlines()

    # Strip leading empty lines
    while not lines[0].strip():
        lines.pop(0)

    return nodes.normalize(u'\n'.join(lines))


def build_render_tree(root, domtree):
    """Process an ElementTree domtree and build a render tree.
    """
    opened = set()
    stack = deque([domtree])
    blackboard = {}
    render_tree = root
    current_node = render_tree

    while stack:
        domtree = stack.pop()

        if domtree not in opened:
            # Open the domtree

            # Build the render node.
            node_class = getattr(nodes, domtree.tag.upper(), nodes.Node)
            current_node = node_class(current_node, domtree, blackboard)

            stack.append(domtree)

            # Queue children
            for el in reversed(domtree):
                stack.append(el)

            opened.add(domtree)
        else:
            # Close the domtree
            current_node = current_node.parent

    return root

## Instruction:
Handle case with empty block
## Code After:
from collections import deque

from antimarkdown import nodes


def render(*domtrees):
    if not domtrees:
        return u''

    root = nodes.Root()
    for dom in domtrees:
        build_render_tree(root, dom)
    lines = unicode(root).rstrip().splitlines()

    # Strip leading empty lines
    while lines and not lines[0].strip():
        lines.pop(0)

    return nodes.normalize(u'\n'.join(lines))


def build_render_tree(root, domtree):
    """Process an ElementTree domtree and build a render tree.
    """
    opened = set()
    stack = deque([domtree])
    blackboard = {}
    render_tree = root
    current_node = render_tree

    while stack:
        domtree = stack.pop()

        if domtree not in opened:
            # Open the domtree

            # Build the render node.
            node_class = getattr(nodes, domtree.tag.upper(), nodes.Node)
            current_node = node_class(current_node, domtree, blackboard)

            stack.append(domtree)

            # Queue children
            for el in reversed(domtree):
                stack.append(el)

            opened.add(domtree)
        else:
            # Close the domtree
            current_node = current_node.parent

    return root
