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import logging
from collections import defaultdict
from django.utils import six
from django.utils.safestring import mark_safe
from .base import (
Node, Template, TemplateSyntaxError, TextNode, Variable, token_kwargs,
from .library import Library
register = Library()
BLOCK_CONTEXT_KEY = 'block_context'
logger = logging.getLogger('django.template')
class ExtendsError(Exception):
class BlockContext(object):
def __init__(self):
# Dictionary of FIFO queues.
self.blocks = defaultdict(list)
def add_blocks(self, blocks):
for name, block in six.iteritems(blocks):
self.blocks[name].insert(0, block)
def pop(self, name):
return self.blocks[name].pop()
except IndexError:
return None
def push(self, name, block):
def get_block(self, name):
return self.blocks[name][-1]
except IndexError:
return None
class BlockNode(Node):
def __init__(self, name, nodelist, parent=None):, self.nodelist, self.parent = name, nodelist, parent
def __repr__(self):
return "<Block Node: %s. Contents: %r>" % (, self.nodelist)
def render(self, context):
block_context = context.render_context.get(BLOCK_CONTEXT_KEY)
with context.push():
if block_context is None:
context['block'] = self
result = self.nodelist.render(context)
push = block = block_context.pop(
if block is None:
block = self
# Create new block so we can store context without thread-safety issues.
block = type(self)(, block.nodelist)
block.context = context
context['block'] = block
result = block.nodelist.render(context)
if push is not None:
block_context.push(, push)
return result
def super(self):
if not hasattr(self, 'context'):
raise TemplateSyntaxError(
"'%s' object has no attribute 'context'. Did you use "
"{{ block.super }} in a base template?" % self.__class__.__name__
render_context = self.context.render_context
if (BLOCK_CONTEXT_KEY in render_context and
render_context[BLOCK_CONTEXT_KEY].get_block( is not None):
return mark_safe(self.render(self.context))
return ''
class ExtendsNode(Node):
must_be_first = True
context_key = 'extends_context'
def __init__(self, nodelist, parent_name, template_dirs=None):
self.nodelist = nodelist
self.parent_name = parent_name
self.template_dirs = template_dirs
self.blocks = { n for n in nodelist.get_nodes_by_type(BlockNode)}
def __repr__(self):
return '<ExtendsNode: extends %s>' % self.parent_name.token
def find_template(self, template_name, context):
This is a wrapper around engine.find_template(). A history is kept in
the render_context attribute between successive extends calls and
passed as the skip argument. This enables extends to work recursively
without extending the same template twice.
# RemovedInDjango20Warning: If any non-recursive loaders are installed
# do a direct template lookup. If the same template name appears twice,
# raise an exception to avoid system recursion.
for loader in context.template.engine.template_loaders:
if not loader.supports_recursion:
history = context.render_context.setdefault(
self.context_key, [context.template.origin.template_name],
if template_name in history:
raise ExtendsError(
"Cannot extend templates recursively when using "
"non-recursive template loaders",
template = context.template.engine.get_template(template_name)
return template
history = context.render_context.setdefault(
self.context_key, [context.template.origin],
template, origin = context.template.engine.find_template(
template_name, skip=history,
return template
def get_parent(self, context):
parent = self.parent_name.resolve(context)
if not parent:
error_msg = "Invalid template name in 'extends' tag: %r." % parent
if self.parent_name.filters or\
isinstance(self.parent_name.var, Variable):
error_msg += " Got this from the '%s' variable." %\
raise TemplateSyntaxError(error_msg)
if isinstance(parent, Template):
# parent is a django.template.Template
return parent
if isinstance(getattr(parent, 'template', None), Template):
# parent is a django.template.backends.django.Template
return parent.template
return self.find_template(parent, context)
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
# 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 = { n for n in
# Call Template._render explicitly so the parser context stays
# the same.
return compiled_parent._render(context)
class IncludeNode(Node):
context_key = '__include_context'
def __init__(self, template, *args, **kwargs):
self.template = template
self.extra_context = kwargs.pop('extra_context', {})
self.isolated_context = kwargs.pop('isolated_context', False)
super(IncludeNode, self).__init__(*args, **kwargs)
def render(self, context):
Render the specified template and context. Cache the template object
in render_context to avoid reparsing and loading when used in a for
template = self.template.resolve(context)
# Does this quack like a Template?
if not callable(getattr(template, 'render', None)):
# If not, we'll try our cache, and get_template()
template_name = template
cache = context.render_context.setdefault(self.context_key, {})
template = cache.get(template_name)
if template is None:
template = context.template.engine.get_template(template_name)
cache[template_name] = template
values = {
name: var.resolve(context)
for name, var in six.iteritems(self.extra_context)
if self.isolated_context:
return template.render(
with context.push(**values):
return template.render(context)
except Exception:
if context.template.engine.debug:
template_name = getattr(context, 'template_name', None) or 'unknown'
"Exception raised while rendering {%% include %%} for "
"template '%s'. Empty string rendered instead.",
return ''
def do_block(parser, token):
Define a block that can be overridden by child templates.
# token.split_contents() isn't useful here because this tag doesn't accept variable as arguments
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.
if block_name in parser.__loaded_blocks:
raise TemplateSyntaxError("'%s' tag with name '%s' appears more than once" % (bits[0], block_name))
except AttributeError: # parser.__loaded_blocks isn't a list yet
parser.__loaded_blocks = [block_name]
nodelist = parser.parse(('endblock',))
# This check is kept for backwards-compatibility. See #3100.
endblock = parser.next_token()
acceptable_endblocks = ('endblock', 'endblock %s' % block_name)
if endblock.contents not in acceptable_endblocks:
parser.invalid_block_tag(endblock, 'endblock', acceptable_endblocks)
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 template itself (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 = 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)
def do_include(parser, token):
Loads a template and renders it with the current context. You can pass
additional context using keyword arguments.
{% include "foo/some_include" %}
{% include "foo/some_include" with bar="BAZZ!" baz="BING!" %}
Use the ``only`` argument to exclude the current context when rendering
the included template::
{% include "foo/some_include" only %}
{% include "foo/some_include" with bar="1" only %}
bits = token.split_contents()
if len(bits) < 2:
raise TemplateSyntaxError(
"%r tag takes at least one argument: the name of the template to "
"be included." % bits[0]
options = {}
remaining_bits = bits[2:]
while remaining_bits:
option = remaining_bits.pop(0)
if option in options:
raise TemplateSyntaxError('The %r option was specified more '
'than once.' % option)
if option == 'with':
value = token_kwargs(remaining_bits, parser, support_legacy=False)
if not value:
raise TemplateSyntaxError('"with" in %r tag needs at least '
'one keyword argument.' % bits[0])
elif option == 'only':
value = True
raise TemplateSyntaxError('Unknown argument for %r tag: %r.' %
(bits[0], option))
options[option] = value
isolated_context = options.get('only', False)
namemap = options.get('with', {})
return IncludeNode(parser.compile_filter(bits[1]), extra_context=namemap,
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