from django.template import TemplateSyntaxError,TemplateDoesNotExist,Variable
from django.template import Library,Node,TextNode
from django.template.loader import get_template
from django.conf import settings
from django.utils.safestring import mark_safe
register = Library()
BLOCK_CONTEXT_KEY = 'block_context'
class ExtendsError(Exception):
pass
class BlockContext(object):
def __init__(self):
# Dictionary of FIFO queues.
self.blocks = {}
def add_blocks(self, blocks):
for name, block in blocks.iteritems():
if name in self.blocks:
self.blocks[name].insert(0, block)
else:
self.blocks[name] = [block]
def pop(self, name):
try:
return self.blocks[name].pop()
except (IndexError, KeyError):
return None
def push(self, name, block):
self.blocks[name].append(block)
def get_block(self, name):
try:
return self.blocks[name][-1]
except (IndexError, KeyError):
return None
class BlockNode(Node):
def __init__(self, name, nodelist, parent=None):
self.name, self.nodelist, self.parent = name, nodelist, parent
def __repr__(self):
return "<Block Node: %s. Contents: %r>" % (self.name, self.nodelist)
def render(self, context):
block_context = context.render_context.get(BLOCK_CONTEXT_KEY)
context.push()
if block_context is None:
context['block'] = self
result = self.nodelist.render(context)
else:
push = block = block_context.pop(self.name)
if block is None:
block = self
# Create new block so we can store context without thread-safety issues.
block = BlockNode(block.name, block.nodelist)
block.context = context
context['block'] = block
result = block.nodelist.render(context)
if push is not None:
block_context.push(self.name, push)
context.pop()
return result
def super(self):
render_context = self.context.render_context
if (BLOCK_CONTEXT_KEY in render_context and
render_context[BLOCK_CONTEXT_KEY].get_block(self.name) is not None):
return mark_safe(self.render(self.context))
return ''
class ExtendsNode(Node):
must_be_first = True
def __init__(self, nodelist, parent_name, parent_name_expr, template_dirs=None):
self.nodelist = nodelist
self.parent_name, self.parent_name_expr = parent_name, parent_name_expr
self.template_dirs = template_dirs
self.blocks = dict([(n.name, n) for n in nodelist.get_nodes_by_type(BlockNode)])
def __repr__(self):
if self.parent_name_expr:
return "<ExtendsNode: extends %s>" % self.parent_name_expr.token
return '<ExtendsNode: extends "%s">' % self.parent_name
def get_parent(self, context):
if self.parent_name_expr:
self.parent_name = self.parent_name_expr.resolve(context)
parent = self.parent_name
if not parent:
error_msg = "Invalid template name in 'extends' tag: %r." % parent
if self.parent_name_expr:
error_msg += " Got this from the '%s' variable." % self.parent_name_expr.token
raise TemplateSyntaxError(error_msg)
if hasattr(parent, 'render'):
return parent # parent is a Template object
return get_template(parent)
def render(self, context):
compiled_parent = self.get_parent(context)
if BLOCK_CONTEXT_KEY not in context.render_context:
context.render_context[BLOCK_CONTEXT_KEY] = BlockContext()
block_context = context.render_context[BLOCK_CONTEXT_KEY]
# Add the block nodes from this node to the block context
block_context.add_blocks(self.blocks)
# If this block's parent doesn't have an extends node it is the root,
# and its block nodes also need to be added to the block context.
for node in compiled_parent.nodelist:
# The ExtendsNode has to be the first non-text node.
if not isinstance(node, TextNode):
if not isinstance(node, ExtendsNode):
blocks = dict([(n.name, n) for n in
compiled_parent.nodelist.get_nodes_by_type(BlockNode)])
block_context.add_blocks(blocks)
break
# Call Template._render explicitly so the parser context stays
# the same.
return compiled_parent._render(context)
class ConstantIncludeNode(Node):
def __init__(self, template_path):
try:
t = get_template(template_path)
self.template = t
except:
if settings.TEMPLATE_DEBUG:
raise
self.template = None
def render(self, context):
if self.template:
return self.template.render(context)
else:
return ''
class IncludeNode(Node):
def __init__(self, template_name):
self.template_name = Variable(template_name)
def render(self, context):
try:
template_name = self.template_name.resolve(context)
t = get_template(template_name)
return t.render(context)
except TemplateSyntaxError, e:
if settings.TEMPLATE_DEBUG:
raise
return ''
except:
return '' # Fail silently for invalid included templates.
def do_block(parser, token):
"""
Define a block that can be overridden by child templates.
"""
bits = token.contents.split()
if len(bits) != 2:
raise TemplateSyntaxError("'%s' tag takes only one argument" % bits[0])
block_name = bits[1]
# Keep track of the names of BlockNodes found in this template, so we can
# check for duplication.
try:
if block_name in parser.__loaded_blocks:
raise TemplateSyntaxError("'%s' tag with name '%s' appears more than once" % (bits[0], block_name))
parser.__loaded_blocks.append(block_name)
except AttributeError: # parser.__loaded_blocks isn't a list yet
parser.__loaded_blocks = [block_name]
nodelist = parser.parse(('endblock', 'endblock %s' % block_name))
parser.delete_first_token()
return BlockNode(block_name, nodelist)
def do_extends(parser, token):
"""
Signal that this template extends a parent template.
This tag may be used in two ways: ``{% extends "base" %}`` (with quotes)
uses the literal value "base" as the name of the parent template to extend,
or ``{% extends variable %}`` uses the value of ``variable`` as either the
name of the parent template to extend (if it evaluates to a string) or as
the parent tempate itelf (if it evaluates to a Template object).
"""
bits = token.split_contents()
if len(bits) != 2:
raise TemplateSyntaxError("'%s' takes one argument" % bits[0])
parent_name, parent_name_expr = None, None
if bits[1][0] in ('"', "'") and bits[1][-1] == bits[1][0]:
parent_name = bits[1][1:-1]
else:
parent_name_expr = parser.compile_filter(bits[1])
nodelist = parser.parse()
if nodelist.get_nodes_by_type(ExtendsNode):
raise TemplateSyntaxError("'%s' cannot appear more than once in the same template" % bits[0])
return ExtendsNode(nodelist, parent_name, parent_name_expr)
def do_include(parser, token):
"""
Loads a template and renders it with the current context.
Example::
{% include "foo/some_include" %}
"""
bits = token.split_contents()
if len(bits) != 2:
raise TemplateSyntaxError("%r tag takes one argument: the name of the template to be included" % bits[0])
path = bits[1]
if path[0] in ('"', "'") and path[-1] == path[0]:
return ConstantIncludeNode(path[1:-1])
return IncludeNode(bits[1])
register.tag('block', do_block)
register.tag('extends', do_extends)
register.tag('include', do_include)
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