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# Wrapper for loading templates from storage of some sort (e.g. filesystem, database).
#
# This uses the TEMPLATE_LOADERS setting, which is a list of loaders to use.
# Each loader is expected to have this interface:
#
# callable(name, dirs=[])
#
# name is the template name.
# dirs is an optional list of directories to search instead of TEMPLATE_DIRS.
#
# Each loader should have an "is_usable" attribute set. This is a boolean that
# specifies whether the loader can be used in this Python installation. Each
# loader is responsible for setting this when it's initialized.
#
# For example, the eggs loader (which is capable of loading templates from
# Python eggs) sets is_usable to False if the "pkg_resources" module isn't
# installed, because pkg_resources is necessary to read eggs.
from django.core.exceptions import ImproperlyConfigured
from django.core.template import Template, Context, Node, TemplateDoesNotExist, TemplateSyntaxError, resolve_variable_with_filters, register_tag
from django.conf.settings import TEMPLATE_LOADERS
template_source_loaders = []
for path in TEMPLATE_LOADERS:
i = path.rfind('.')
module, attr = path[:i], path[i+1:]
try:
mod = __import__(module, globals(), locals(), [attr])
except ImportError, e:
raise ImproperlyConfigured, 'Error importing template source loader %s: "%s"' % (module, e)
try:
func = getattr(mod, attr)
except AttributeError:
raise ImproperlyConfigured, 'Module "%s" does not define a "%s" callable template source loader' % (module, attr)
if not func.is_usable:
import warnings
warnings.warn("Your TEMPLATE_LOADERS setting includes %r, but your Python installation doesn't support that type of template loading. Consider removing that line from TEMPLATE_LOADERS." % path)
else:
template_source_loaders.append(func)
def load_template_source(name, dirs=None):
for loader in template_source_loaders:
try:
return loader(name, dirs)
except TemplateDoesNotExist:
pass
raise TemplateDoesNotExist, name
class ExtendsError(Exception):
pass
def get_template(template_name):
"""
Returns a compiled Template object for the given template name,
handling template inheritance recursively.
"""
return get_template_from_string(load_template_source(template_name))
def get_template_from_string(source):
"""
Returns a compiled Template object for the given template code,
handling template inheritance recursively.
"""
return Template(source)
def render_to_string(template_name, dictionary=None, context_instance=None):
"""
Loads the given template_name and renders it with the given dictionary as
context. The template_name may be a string to load a single template using
get_template, or it may be a tuple to use select_template to find one of
the templates in the list. Returns a string.
"""
dictionary = dictionary or {}
if isinstance(template_name, (list, tuple)):
t = select_template(template_name)
else:
t = get_template(template_name)
if context_instance:
context_instance.update(dictionary)
else:
context_instance = Context(dictionary)
return t.render(context_instance)
def select_template(template_name_list):
"Given a list of template names, returns the first that can be loaded."
for template_name in template_name_list:
try:
return get_template(template_name)
except TemplateDoesNotExist:
continue
# If we get here, none of the templates could be loaded
raise TemplateDoesNotExist, ', '.join(template_name_list)
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):
context.push()
# Save context in case of block.super().
self.context = context
context['block'] = self
result = self.nodelist.render(context)
context.pop()
return result
def super(self):
if self.parent:
return self.parent.render(self.context)
return ''
def add_parent(self, nodelist):
if self.parent:
self.parent.add_parent(nodelist)
else:
self.parent = BlockNode(self.name, nodelist)
class ExtendsNode(Node):
def __init__(self, nodelist, parent_name, parent_name_var, template_dirs=None):
self.nodelist = nodelist
self.parent_name, self.parent_name_var = parent_name, parent_name_var
self.template_dirs = template_dirs
def get_parent(self, context):
if self.parent_name_var:
self.parent_name = resolve_variable_with_filters(self.parent_name_var, context)
parent = self.parent_name
if not parent:
error_msg = "Invalid template name in 'extends' tag: %r." % parent
if self.parent_name_var:
error_msg += " Got this from the %r variable." % self.parent_name_var
raise TemplateSyntaxError, error_msg
try:
return get_template_from_string(load_template_source(parent, self.template_dirs))
except TemplateDoesNotExist:
raise TemplateSyntaxError, "Template %r cannot be extended, because it doesn't exist" % parent
def render(self, context):
compiled_parent = self.get_parent(context)
parent_is_child = isinstance(compiled_parent.nodelist[0], ExtendsNode)
parent_blocks = dict([(n.name, n) for n in compiled_parent.nodelist.get_nodes_by_type(BlockNode)])
for block_node in self.nodelist.get_nodes_by_type(BlockNode):
# Check for a BlockNode with this node's name, and replace it if found.
try:
parent_block = parent_blocks[block_node.name]
except KeyError:
# This BlockNode wasn't found in the parent template, but the
# parent block might be defined in the parent's *parent*, so we
# add this BlockNode to the parent's ExtendsNode nodelist, so
# it'll be checked when the parent node's render() is called.
if parent_is_child:
compiled_parent.nodelist[0].nodelist.append(block_node)
else:
# Keep any existing parents and add a new one. Used by BlockNode.
parent_block.parent = block_node.parent
parent_block.add_parent(parent_block.nodelist)
parent_block.nodelist = block_node.nodelist
return compiled_parent.render(context)
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',))
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 ``{% entends variable %}`` uses the value of ``variable`` as the name
of the parent template to extend.
"""
bits = token.contents.split()
if len(bits) != 2:
raise TemplateSyntaxError, "'%s' takes one argument" % bits[0]
parent_name, parent_name_var = None, None
if (bits[1].startswith('"') and bits[1].endswith('"')) or (bits[1].startswith("'") and bits[1].endswith("'")):
parent_name = bits[1][1:-1]
else:
parent_name_var = 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_var)
register_tag('block', do_block)
register_tag('extends', do_extends)
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