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This is the Django template system.
How it works:
The Lexer.tokenize() function converts a template string (i.e., a string containing
markup with custom template tags) to tokens, which can be either plain text
(TOKEN_TEXT), variables (TOKEN_VAR) or block statements (TOKEN_BLOCK).
The Parser() class takes a list of tokens in its constructor, and its parse()
method returns a compiled template -- which is, under the hood, a list of
Node objects.
Each Node is responsible for creating some sort of output -- e.g. simple text
(TextNode), variable values in a given context (VariableNode), results of basic
logic (IfNode), results of looping (ForNode), or anything else. The core Node
types are TextNode, VariableNode, IfNode and ForNode, but plugin modules can
define their own custom node types.
Each Node has a render() method, which takes a Context and returns a string of
the rendered node. For example, the render() method of a Variable Node returns
the variable's value as a string. The render() method of a ForNode returns the
rendered output of whatever was inside the loop, recursively.
The Template class is a convenient wrapper that takes care of template
compilation and rendering.
The only thing you should ever use directly in this file is the Template class.
Create a compiled template object with a template_string, then call render()
with a context. In the compilation stage, the TemplateSyntaxError exception
will be raised if the template doesn't have proper syntax.
Sample code:
>>> from django import template
>>> s = u'<html>{% if test %}<h1>{{ varvalue }}</h1>{% endif %}</html>'
>>> t = template.Template(s)
(t is now a compiled template, and its render() method can be called multiple
times with multiple contexts)
>>> c = template.Context({'test':True, 'varvalue': 'Hello'})
>>> t.render(c)
>>> c = template.Context({'test':False, 'varvalue': 'Hello'})
>>> t.render(c)
from __future__ import unicode_literals
import re
import warnings
from functools import partial
from importlib import import_module
from inspect import getargspec, getcallargs
from django.apps import apps
from django.template.context import ( # NOQA: imported for backwards compatibility
BaseContext, Context, ContextPopException, RequestContext,
from django.utils import lru_cache, six
from django.utils.deprecation import (
RemovedInDjango20Warning, RemovedInDjango21Warning,
from django.utils.encoding import (
force_str, force_text, python_2_unicode_compatible,
from django.utils.formats import localize
from django.utils.html import conditional_escape
from django.utils.itercompat import is_iterable
from django.utils.module_loading import module_has_submodule
from django.utils.safestring import (
EscapeData, SafeData, mark_for_escaping, mark_safe,
from django.utils.text import (
get_text_list, smart_split, unescape_string_literal,
from django.utils.timezone import template_localtime
from django.utils.translation import pgettext_lazy, ugettext_lazy
# template syntax constants
ALLOWED_VARIABLE_CHARS = ('abcdefghijklmnopqrstuvwxyz'
# what to report as the origin for templates that come from non-loader sources
# (e.g. strings)
UNKNOWN_SOURCE = '<unknown source>'
# match a variable or block tag and capture the entire tag, including start/end
# delimiters
tag_re = (re.compile('(%s.*?%s|%s.*?%s|%s.*?%s)' %
(re.escape(BLOCK_TAG_START), re.escape(BLOCK_TAG_END),
re.escape(COMMENT_TAG_START), re.escape(COMMENT_TAG_END))))
# global dictionary of libraries that have been loaded using get_library
libraries = {}
# global list of libraries to load by default for a new parser
builtins = []
class TemplateSyntaxError(Exception):
class TemplateDoesNotExist(Exception):
class TemplateEncodingError(Exception):
class VariableDoesNotExist(Exception):
def __init__(self, msg, params=()):
self.msg = msg
self.params = params
def __str__(self):
return self.msg % tuple(force_text(p, errors='replace') for p in self.params)
class InvalidTemplateLibrary(Exception):
class Origin(object):
def __init__(self, name): = name
def reload(self):
raise NotImplementedError('subclasses of Origin must provide a reload() method')
def __str__(self):
class StringOrigin(Origin):
def __init__(self, source):
super(StringOrigin, self).__init__(UNKNOWN_SOURCE)
self.source = source
def reload(self):
return self.source
class Template(object):
def __init__(self, template_string, origin=None, name=None, engine=None):
template_string = force_text(template_string)
except UnicodeDecodeError:
raise TemplateEncodingError("Templates can only be constructed "
"from unicode or UTF-8 strings.")
# If Template is instantiated directly rather than from an Engine and
# exactly one Django template engine is configured, use that engine.
# This is required to preserve backwards-compatibility for direct use
# e.g. Template('...').render(Context({...}))
if engine is None:
from .engine import Engine
engine = Engine.get_default()
if engine.debug and origin is None:
origin = StringOrigin(template_string)
self.nodelist = engine.compile_string(template_string, origin) = name
self.origin = origin
self.engine = engine
def __iter__(self):
for node in self.nodelist:
for subnode in node:
yield subnode
def _render(self, context):
return self.nodelist.render(context)
def render(self, context):
"Display stage -- can be called many times"
if context.template is None:
with context.bind_template(self):
return self._render(context)
return self._render(context)
class Token(object):
def __init__(self, token_type, contents):
# token_type must be TOKEN_TEXT, TOKEN_VAR, TOKEN_BLOCK or
self.token_type, self.contents = token_type, contents
self.lineno = None
def __str__(self):
token_name = TOKEN_MAPPING[self.token_type]
return ('<%s token: "%s...">' %
(token_name, self.contents[:20].replace('\n', '')))
def split_contents(self):
split = []
bits = iter(smart_split(self.contents))
for bit in bits:
# Handle translation-marked template pieces
if bit.startswith('_("') or bit.startswith("_('"):
sentinal = bit[2] + ')'
trans_bit = [bit]
while not bit.endswith(sentinal):
bit = next(bits)
bit = ' '.join(trans_bit)
return split
class Lexer(object):
def __init__(self, template_string, origin):
self.template_string = template_string
self.origin = origin
self.lineno = 1
self.verbatim = False
def tokenize(self):
Return a list of tokens from a given template_string.
in_tag = False
result = []
for bit in tag_re.split(self.template_string):
if bit:
result.append(self.create_token(bit, in_tag))
in_tag = not in_tag
return result
def create_token(self, token_string, in_tag):
Convert the given token string into a new Token object and return it.
If in_tag is True, we are processing something that matched a tag,
otherwise it should be treated as a literal string.
if in_tag and token_string.startswith(BLOCK_TAG_START):
# The [2:-2] ranges below strip off *_TAG_START and *_TAG_END.
# We could do len(BLOCK_TAG_START) to be more "correct", but we've
# hard-coded the 2s here for performance. And it's not like
# the TAG_START values are going to change anytime, anyway.
block_content = token_string[2:-2].strip()
if self.verbatim and block_content == self.verbatim:
self.verbatim = False
if in_tag and not self.verbatim:
if token_string.startswith(VARIABLE_TAG_START):
token = Token(TOKEN_VAR, token_string[2:-2].strip())
elif token_string.startswith(BLOCK_TAG_START):
if block_content[:9] in ('verbatim', 'verbatim '):
self.verbatim = 'end%s' % block_content
token = Token(TOKEN_BLOCK, block_content)
elif token_string.startswith(COMMENT_TAG_START):
content = ''
if token_string.find(TRANSLATOR_COMMENT_MARK):
content = token_string[2:-2].strip()
token = Token(TOKEN_COMMENT, content)
token = Token(TOKEN_TEXT, token_string)
token.lineno = self.lineno
self.lineno += token_string.count('\n')
return token
class Parser(object):
def __init__(self, tokens):
self.tokens = tokens
self.tags = {}
self.filters = {}
for lib in builtins:
def parse(self, parse_until=None):
if parse_until is None:
parse_until = []
nodelist = self.create_nodelist()
while self.tokens:
token = self.next_token()
# Use the raw values here for TOKEN_* for a tiny performance boost.
if token.token_type == 0: # TOKEN_TEXT
self.extend_nodelist(nodelist, TextNode(token.contents), token)
elif token.token_type == 1: # TOKEN_VAR
if not token.contents:
filter_expression = self.compile_filter(token.contents)
except TemplateSyntaxError as e:
if not self.compile_filter_error(token, e):
var_node = self.create_variable_node(filter_expression)
self.extend_nodelist(nodelist, var_node, token)
elif token.token_type == 2: # TOKEN_BLOCK
command = token.contents.split()[0]
except IndexError:
if command in parse_until:
# put token back on token list so calling
# code knows why it terminated
return nodelist
# execute callback function for this tag and append
# resulting node
self.enter_command(command, token)
compile_func = self.tags[command]
except KeyError:
self.invalid_block_tag(token, command, parse_until)
compiled_result = compile_func(self, token)
except TemplateSyntaxError as e:
if not self.compile_function_error(token, e):
self.extend_nodelist(nodelist, compiled_result, token)
if parse_until:
return nodelist
def skip_past(self, endtag):
while self.tokens:
token = self.next_token()
if token.token_type == TOKEN_BLOCK and token.contents == endtag:
def create_variable_node(self, filter_expression):
return VariableNode(filter_expression)
def create_nodelist(self):
return NodeList()
def extend_nodelist(self, nodelist, node, token):
if node.must_be_first and nodelist:
if nodelist.contains_nontext:
raise AttributeError
except AttributeError:
raise TemplateSyntaxError("%r must be the first tag "
"in the template." % node)
if isinstance(nodelist, NodeList) and not isinstance(node, TextNode):
nodelist.contains_nontext = True
def enter_command(self, command, token):
def exit_command(self):
def error(self, token, msg):
return TemplateSyntaxError(msg)
def empty_variable(self, token):
raise self.error(token, "Empty variable tag")
def empty_block_tag(self, token):
raise self.error(token, "Empty block tag")
def invalid_block_tag(self, token, command, parse_until=None):
if parse_until:
raise self.error(token, "Invalid block tag: '%s', expected %s" %
(command, get_text_list(["'%s'" % p for p in parse_until])))
raise self.error(token, "Invalid block tag: '%s'" % command)
def unclosed_block_tag(self, parse_until):
raise self.error(None, "Unclosed tags: %s " % ', '.join(parse_until))
def compile_filter_error(self, token, e):
def compile_function_error(self, token, e):
def next_token(self):
return self.tokens.pop(0)
def prepend_token(self, token):
self.tokens.insert(0, token)
def delete_first_token(self):
del self.tokens[0]
def add_library(self, lib):
def compile_filter(self, token):
Convenient wrapper for FilterExpression
return FilterExpression(token, self)
def find_filter(self, filter_name):
if filter_name in self.filters:
return self.filters[filter_name]
raise TemplateSyntaxError("Invalid filter: '%s'" % filter_name)
class TokenParser(object):
Subclass this and implement the top() method to parse a template line.
When instantiating the parser, pass in the line from the Django template
The parser's "tagname" instance-variable stores the name of the tag that
the filter was called with.
def __init__(self, subject):
self.subject = subject
self.pointer = 0
self.backout = []
self.tagname = self.tag()
def top(self):
Overload this method to do the actual parsing and return the result.
raise NotImplementedError('subclasses of Tokenparser must provide a top() method')
def more(self):
Returns True if there is more stuff in the tag.
return self.pointer < len(self.subject)
def back(self):
Undoes the last microparser. Use this for lookahead and backtracking.
if not len(self.backout):
raise TemplateSyntaxError("back called without some previous "
self.pointer = self.backout.pop()
def tag(self):
A microparser that just returns the next tag from the line.
subject = self.subject
i = self.pointer
if i >= len(subject):
raise TemplateSyntaxError("expected another tag, found "
"end of string: %s" % subject)
p = i
while i < len(subject) and subject[i] not in (' ', '\t'):
i += 1
s = subject[p:i]
while i < len(subject) and subject[i] in (' ', '\t'):
i += 1
self.pointer = i
return s
def value(self):
A microparser that parses for a value: some string constant or
variable name.
subject = self.subject
i = self.pointer
def next_space_index(subject, i):
Increment pointer until a real space (i.e. a space not within
quotes) is encountered
while i < len(subject) and subject[i] not in (' ', '\t'):
if subject[i] in ('"', "'"):
c = subject[i]
i += 1
while i < len(subject) and subject[i] != c:
i += 1
if i >= len(subject):
raise TemplateSyntaxError("Searching for value. "
"Unexpected end of string in column %d: %s" %
(i, subject))
i += 1
return i
if i >= len(subject):
raise TemplateSyntaxError("Searching for value. Expected another "
"value but found end of string: %s" %
if subject[i] in ('"', "'"):
p = i
i += 1
while i < len(subject) and subject[i] != subject[p]:
i += 1
if i >= len(subject):
raise TemplateSyntaxError("Searching for value. Unexpected "
"end of string in column %d: %s" %
(i, subject))
i += 1
# Continue parsing until next "real" space,
# so that filters are also included
i = next_space_index(subject, i)
res = subject[p:i]
while i < len(subject) and subject[i] in (' ', '\t'):
i += 1
self.pointer = i
return res
p = i
i = next_space_index(subject, i)
s = subject[p:i]
while i < len(subject) and subject[i] in (' ', '\t'):
i += 1
self.pointer = i
return s
# This only matches constant *strings* (things in quotes or marked for
# translation). Numbers are treated as variables for implementation reasons
# (so that they retain their type when passed to filters).
constant_string = r"""
""" % {
'strdq': r'"[^"\\]*(?:\\.[^"\\]*)*"', # double-quoted string
'strsq': r"'[^'\\]*(?:\\.[^'\\]*)*'", # single-quoted string
'i18n_open': re.escape("_("),
'i18n_close': re.escape(")"),
constant_string = constant_string.replace("\n", "")
filter_raw_string = r"""
)""" % {
'constant': constant_string,
'num': r'[-+\.]?\d[\d\.e]*',
'var_chars': "\w\.",
'filter_sep': re.escape(FILTER_SEPARATOR),
'arg_sep': re.escape(FILTER_ARGUMENT_SEPARATOR),
filter_re = re.compile(filter_raw_string, re.UNICODE | re.VERBOSE)
class FilterExpression(object):
Parses a variable token and its optional filters (all as a single string),
and return a list of tuples of the filter name and arguments.
>>> token = 'variable|default:"Default value"|date:"Y-m-d"'
>>> p = Parser('')
>>> fe = FilterExpression(token, p)
>>> len(fe.filters)
>>> fe.var
<Variable: 'variable'>
def __init__(self, token, parser):
self.token = token
matches = filter_re.finditer(token)
var_obj = None
filters = []
upto = 0
for match in matches:
start = match.start()
if upto != start:
raise TemplateSyntaxError("Could not parse some characters: "
"%s|%s|%s" %
(token[:upto], token[upto:start],
if var_obj is None:
var, constant ="var", "constant")
if constant:
var_obj = Variable(constant).resolve({})
except VariableDoesNotExist:
var_obj = None
elif var is None:
raise TemplateSyntaxError("Could not find variable at "
"start of %s." % token)
var_obj = Variable(var)
filter_name ="filter_name")
args = []
constant_arg, var_arg ="constant_arg", "var_arg")
if constant_arg:
args.append((False, Variable(constant_arg).resolve({})))
elif var_arg:
args.append((True, Variable(var_arg)))
filter_func = parser.find_filter(filter_name)
self.args_check(filter_name, filter_func, args)
filters.append((filter_func, args))
upto = match.end()
if upto != len(token):
raise TemplateSyntaxError("Could not parse the remainder: '%s' "
"from '%s'" % (token[upto:], token))
self.filters = filters
self.var = var_obj
def resolve(self, context, ignore_failures=False):
if isinstance(self.var, Variable):
obj = self.var.resolve(context)
except VariableDoesNotExist:
if ignore_failures:
obj = None
string_if_invalid = context.template.engine.string_if_invalid
if string_if_invalid:
if '%s' in string_if_invalid:
return string_if_invalid % self.var
return string_if_invalid
obj = string_if_invalid
obj = self.var
for func, args in self.filters:
arg_vals = []
for lookup, arg in args:
if not lookup:
if getattr(func, 'expects_localtime', False):
obj = template_localtime(obj, context.use_tz)
if getattr(func, 'needs_autoescape', False):
new_obj = func(obj, autoescape=context.autoescape, *arg_vals)
new_obj = func(obj, *arg_vals)
if getattr(func, 'is_safe', False) and isinstance(obj, SafeData):
obj = mark_safe(new_obj)
elif isinstance(obj, EscapeData):
obj = mark_for_escaping(new_obj)
obj = new_obj
return obj
def args_check(name, func, provided):
provided = list(provided)
# First argument, filter input, is implied.
plen = len(provided) + 1
# Check to see if a decorator is providing the real function.
func = getattr(func, '_decorated_function', func)
args, varargs, varkw, defaults = getargspec(func)
alen = len(args)
dlen = len(defaults or [])
# Not enough OR Too many
if plen < (alen - dlen) or plen > alen:
raise TemplateSyntaxError("%s requires %d arguments, %d provided" %
(name, alen - dlen, plen))
return True
args_check = staticmethod(args_check)
def __str__(self):
return self.token
def resolve_variable(path, context):
Returns the resolved variable, which may contain attribute syntax, within
the given context.
Deprecated; use the Variable class instead.
warnings.warn("resolve_variable() is deprecated. Use django.template."
"Variable(path).resolve(context) instead",
RemovedInDjango20Warning, stacklevel=2)
return Variable(path).resolve(context)
class Variable(object):
A template variable, resolvable against a given context. The variable may
be a hard-coded string (if it begins and ends with single or double quote
>>> c = {'article': {'section':u'News'}}
>>> Variable('article.section').resolve(c)
>>> Variable('article').resolve(c)
{'section': u'News'}
>>> class AClass: pass
>>> c = AClass()
>>> c.article = AClass()
>>> c.article.section = u'News'
(The example assumes VARIABLE_ATTRIBUTE_SEPARATOR is '.')
def __init__(self, var):
self.var = var
self.literal = None
self.lookups = None
self.translate = False
self.message_context = None
if not isinstance(var, six.string_types):
raise TypeError(
"Variable must be a string or number, got %s" % type(var))
# First try to treat this variable as a number.
# Note that this could cause an OverflowError here that we're not
# catching. Since this should only happen at compile time, that's
# probably OK.
self.literal = float(var)
# So it's a float... is it an int? If the original value contained a
# dot or an "e" then it was a float, not an int.
if '.' not in var and 'e' not in var.lower():
self.literal = int(self.literal)
# "2." is invalid
if var.endswith('.'):
raise ValueError
except ValueError:
# A ValueError means that the variable isn't a number.
if var.startswith('_(') and var.endswith(')'):
# The result of the lookup should be translated at rendering
# time.
self.translate = True
var = var[2:-1]
# If it's wrapped with quotes (single or double), then
# we're also dealing with a literal.
self.literal = mark_safe(unescape_string_literal(var))
except ValueError:
# Otherwise we'll set self.lookups so that resolve() knows we're
# dealing with a bonafide variable
if var.find(VARIABLE_ATTRIBUTE_SEPARATOR + '_') > -1 or var[0] == '_':
raise TemplateSyntaxError("Variables and attributes may "
"not begin with underscores: '%s'" %
self.lookups = tuple(var.split(VARIABLE_ATTRIBUTE_SEPARATOR))
def resolve(self, context):
"""Resolve this variable against a given context."""
if self.lookups is not None:
# We're dealing with a variable that needs to be resolved
value = self._resolve_lookup(context)
# We're dealing with a literal, so it's already been "resolved"
value = self.literal
if self.translate:
if self.message_context:
return pgettext_lazy(self.message_context, value)
return ugettext_lazy(value)
return value
def __repr__(self):
return "<%s: %r>" % (self.__class__.__name__, self.var)
def __str__(self):
return self.var
def _resolve_lookup(self, context):
Performs resolution of a real variable (i.e. not a literal) against the
given context.
As indicated by the method's name, this method is an implementation
detail and shouldn't be called by external code. Use Variable.resolve()
current = context
try: # catch-all for silent variable failures
for bit in self.lookups:
try: # dictionary lookup
current = current[bit]
# ValueError/IndexError are for numpy.array lookup on
# numpy < 1.9 and 1.9+ respectively
except (TypeError, AttributeError, KeyError, ValueError, IndexError):
try: # attribute lookup
# Don't return class attributes if the class is the context:
if isinstance(current, BaseContext) and getattr(type(current), bit):
raise AttributeError
current = getattr(current, bit)
except (TypeError, AttributeError) as e:
# Reraise an AttributeError raised by a @property
if (isinstance(e, AttributeError) and
not isinstance(current, BaseContext) and bit in dir(current)):
try: # list-index lookup
current = current[int(bit)]
except (IndexError, # list index out of range
ValueError, # invalid literal for int()
KeyError, # current is a dict without `int(bit)` key
TypeError): # unsubscriptable object
raise VariableDoesNotExist("Failed lookup for key "
"[%s] in %r",
(bit, current)) # missing attribute
if callable(current):
if getattr(current, 'do_not_call_in_templates', False):
elif getattr(current, 'alters_data', False):
current = context.template.engine.string_if_invalid
try: # method call (assuming no args required)
current = current()
except TypeError:
except TypeError: # arguments *were* required
current = context.template.engine.string_if_invalid # invalid method call
except Exception as e:
if getattr(e, 'silent_variable_failure', False):
current = context.template.engine.string_if_invalid
return current
class Node(object):
# Set this to True for nodes that must be first in the template (although
# they can be preceded by text nodes.
must_be_first = False
child_nodelists = ('nodelist',)
def render(self, context):
Return the node rendered as a string.
def __iter__(self):
yield self
def get_nodes_by_type(self, nodetype):
Return a list of all nodes (within this node and its nodelist)
of the given type
nodes = []
if isinstance(self, nodetype):
for attr in self.child_nodelists:
nodelist = getattr(self, attr, None)
if nodelist:
return nodes
class NodeList(list):
# Set to True the first time a non-TextNode is inserted by
# extend_nodelist().
contains_nontext = False
def render(self, context):
bits = []
for node in self:
if isinstance(node, Node):
bit = self.render_node(node, context)
bit = node
return mark_safe(''.join(bits))
def get_nodes_by_type(self, nodetype):
"Return a list of all nodes of the given type"
nodes = []
for node in self:
return nodes
def render_node(self, node, context):
return node.render(context)
class TextNode(Node):
def __init__(self, s):
self.s = s
def __repr__(self):
return force_str("<Text Node: '%s'>" % self.s[:25], 'ascii',
def render(self, context):
return self.s
def render_value_in_context(value, context):
Converts any value to a string to become part of a rendered template. This
means escaping, if required, and conversion to a unicode object. If value
is a string, it is expected to have already been translated.
value = template_localtime(value, use_tz=context.use_tz)
value = localize(value, use_l10n=context.use_l10n)
value = force_text(value)
if ((context.autoescape and not isinstance(value, SafeData)) or
isinstance(value, EscapeData)):
return conditional_escape(value)
return value
class VariableNode(Node):
def __init__(self, filter_expression):
self.filter_expression = filter_expression
def __repr__(self):
return "<Variable Node: %s>" % self.filter_expression
def render(self, context):
output = self.filter_expression.resolve(context)
except UnicodeDecodeError:
# Unicode conversion can fail sometimes for reasons out of our
# control (e.g. exception rendering). In that case, we fail
# quietly.
return ''
return render_value_in_context(output, context)
# Regex for token keyword arguments
kwarg_re = re.compile(r"(?:(\w+)=)?(.+)")
def token_kwargs(bits, parser, support_legacy=False):
A utility method for parsing token keyword arguments.
:param bits: A list containing remainder of the token (split by spaces)
that is to be checked for arguments. Valid arguments will be removed
from this list.
:param support_legacy: If set to true ``True``, the legacy format
``1 as foo`` will be accepted. Otherwise, only the standard ``foo=1``
format is allowed.
:returns: A dictionary of the arguments retrieved from the ``bits`` token
There is no requirement for all remaining token ``bits`` to be keyword
arguments, so the dictionary will be returned as soon as an invalid
argument format is reached.
if not bits:
return {}
match = kwarg_re.match(bits[0])
kwarg_format = match and
if not kwarg_format:
if not support_legacy:
return {}
if len(bits) < 3 or bits[1] != 'as':
return {}
kwargs = {}
while bits:
if kwarg_format:
match = kwarg_re.match(bits[0])
if not match or not
return kwargs
key, value = match.groups()
del bits[:1]
if len(bits) < 3 or bits[1] != 'as':
return kwargs
key, value = bits[2], bits[0]
del bits[:3]
kwargs[key] = parser.compile_filter(value)
if bits and not kwarg_format:
if bits[0] != 'and':
return kwargs
del bits[:1]
return kwargs
def parse_bits(parser, bits, params, varargs, varkw, defaults,
takes_context, name):
Parses bits for template tag helpers simple_tag and inclusion_tag, in
particular by detecting syntax errors and by extracting positional and
keyword arguments.
if takes_context:
if params[0] == 'context':
params = params[1:]
raise TemplateSyntaxError(
"'%s' is decorated with takes_context=True so it must "
"have a first argument of 'context'" % name)
args = []
kwargs = {}
unhandled_params = list(params)
for bit in bits:
# First we try to extract a potential kwarg from the bit
kwarg = token_kwargs([bit], parser)
if kwarg:
# The kwarg was successfully extracted
param, value = list(six.iteritems(kwarg))[0]
if param not in params and varkw is None:
# An unexpected keyword argument was supplied
raise TemplateSyntaxError(
"'%s' received unexpected keyword argument '%s'" %
(name, param))
elif param in kwargs:
# The keyword argument has already been supplied once
raise TemplateSyntaxError(
"'%s' received multiple values for keyword argument '%s'" %
(name, param))
# All good, record the keyword argument
kwargs[str(param)] = value
if param in unhandled_params:
# If using the keyword syntax for a positional arg, then
# consume it.
if kwargs:
raise TemplateSyntaxError(
"'%s' received some positional argument(s) after some "
"keyword argument(s)" % name)
# Record the positional argument
# Consume from the list of expected positional arguments
except IndexError:
if varargs is None:
raise TemplateSyntaxError(
"'%s' received too many positional arguments" %
if defaults is not None:
# Consider the last n params handled, where n is the
# number of defaults.
unhandled_params = unhandled_params[:-len(defaults)]
if unhandled_params:
# Some positional arguments were not supplied
raise TemplateSyntaxError(
"'%s' did not receive value(s) for the argument(s): %s" %
(name, ", ".join("'%s'" % p for p in unhandled_params)))
return args, kwargs
def generic_tag_compiler(parser, token, params, varargs, varkw, defaults,
name, takes_context, node_class):
Returns a template.Node subclass.
bits = token.split_contents()[1:]
args, kwargs = parse_bits(parser, bits, params, varargs, varkw,
defaults, takes_context, name)
return node_class(takes_context, args, kwargs)
class TagHelperNode(Node):
Base class for tag helper nodes such as SimpleNode and InclusionNode.
Manages the positional and keyword arguments to be passed to the decorated
def __init__(self, takes_context, args, kwargs):
self.takes_context = takes_context
self.args = args
self.kwargs = kwargs
def get_resolved_arguments(self, context):
resolved_args = [var.resolve(context) for var in self.args]
if self.takes_context:
resolved_args = [context] + resolved_args
resolved_kwargs = {k: v.resolve(context) for k, v in self.kwargs.items()}
return resolved_args, resolved_kwargs
class Library(object):
def __init__(self):
self.filters = {}
self.tags = {}
def tag(self, name=None, compile_function=None):
if name is None and compile_function is None:
# @register.tag()
return self.tag_function
elif name is not None and compile_function is None:
if callable(name):
# @register.tag
return self.tag_function(name)
# @register.tag('somename') or @register.tag(name='somename')
def dec(func):
return self.tag(name, func)
return dec
elif name is not None and compile_function is not None:
# register.tag('somename', somefunc)
self.tags[name] = compile_function
return compile_function
raise InvalidTemplateLibrary("Unsupported arguments to "
"Library.tag: (%r, %r)", (name, compile_function))
def tag_function(self, func):
self.tags[getattr(func, "_decorated_function", func).__name__] = func
return func
def filter(self, name=None, filter_func=None, **flags):
if name is None and filter_func is None:
# @register.filter()
def dec(func):
return self.filter_function(func, **flags)
return dec
elif name is not None and filter_func is None:
if callable(name):
# @register.filter
return self.filter_function(name, **flags)
# @register.filter('somename') or @register.filter(name='somename')
def dec(func):
return self.filter(name, func, **flags)
return dec
elif name is not None and filter_func is not None:
# register.filter('somename', somefunc)
self.filters[name] = filter_func
for attr in ('expects_localtime', 'is_safe', 'needs_autoescape'):
if attr in flags:
value = flags[attr]
# set the flag on the filter for FilterExpression.resolve
setattr(filter_func, attr, value)
# set the flag on the innermost decorated function
# for decorators that need it e.g. stringfilter
if hasattr(filter_func, "_decorated_function"):
setattr(filter_func._decorated_function, attr, value)
filter_func._filter_name = name
return filter_func
raise InvalidTemplateLibrary("Unsupported arguments to "
"Library.filter: (%r, %r)", (name, filter_func))
def filter_function(self, func, **flags):
name = getattr(func, "_decorated_function", func).__name__
return self.filter(name, func, **flags)
def simple_tag(self, func=None, takes_context=None, name=None):
def dec(func):
params, varargs, varkw, defaults = getargspec(func)
class SimpleNode(TagHelperNode):
def __init__(self, takes_context, args, kwargs, target_var):
super(SimpleNode, self).__init__(takes_context, args, kwargs)
self.target_var = target_var
def render(self, context):
resolved_args, resolved_kwargs = self.get_resolved_arguments(context)
output = func(*resolved_args, **resolved_kwargs)
if self.target_var is not None:
context[self.target_var] = output
return ''
return output
function_name = (name or
getattr(func, '_decorated_function', func).__name__)
def compile_func(parser, token):
bits = token.split_contents()[1:]
target_var = None
if len(bits) >= 2 and bits[-2] == 'as':
target_var = bits[-1]
bits = bits[:-2]
args, kwargs = parse_bits(parser, bits, params,
varargs, varkw, defaults, takes_context, function_name)
return SimpleNode(takes_context, args, kwargs, target_var)
compile_func.__doc__ = func.__doc__
self.tag(function_name, compile_func)
return func
if func is None:
# @register.simple_tag(...)
return dec
elif callable(func):
# @register.simple_tag
return dec(func)
raise TemplateSyntaxError("Invalid arguments provided to simple_tag")
def assignment_tag(self, func=None, takes_context=None, name=None):
"assignment_tag() is deprecated. Use simple_tag() instead",
return self.simple_tag(func, takes_context, name)
def inclusion_tag(self, file_name, takes_context=False, name=None):
def dec(func):
params, varargs, varkw, defaults = getargspec(func)
class InclusionNode(TagHelperNode):
def render(self, context):
resolved_args, resolved_kwargs = self.get_resolved_arguments(context)
_dict = func(*resolved_args, **resolved_kwargs)
if not getattr(self, 'nodelist', False):
if isinstance(file_name, Template):
t = file_name
elif isinstance(getattr(file_name, 'template', None), Template):
t = file_name.template
elif not isinstance(file_name, six.string_types) and is_iterable(file_name):
t = context.template.engine.select_template(file_name)
t = context.template.engine.get_template(file_name)
self.nodelist = t.nodelist
new_context =
# Copy across the CSRF token, if present, because
# inclusion tags are often used for forms, and we need
# instructions for using CSRF protection to be as simple
# as possible.
csrf_token = context.get('csrf_token', None)
if csrf_token is not None:
new_context['csrf_token'] = csrf_token
return self.nodelist.render(new_context)
function_name = (name or
getattr(func, '_decorated_function', func).__name__)
compile_func = partial(generic_tag_compiler,
params=params, varargs=varargs, varkw=varkw,
defaults=defaults, name=function_name,
takes_context=takes_context, node_class=InclusionNode)
compile_func.__doc__ = func.__doc__
self.tag(function_name, compile_func)
return func
return dec
def is_library_missing(name):
"""Check if library that failed to load cannot be found under any
templatetags directory or does exist but fails to import.
Non-existing condition is checked recursively for each subpackage in cases
like <appdir>/templatetags/subpackage/package/
# Don't bother to check if '.' is in name since any name will be prefixed
# with some template root.
path, module = name.rsplit('.', 1)
package = import_module(path)
return not module_has_submodule(package, module)
except ImportError:
return is_library_missing(path)
def import_library(taglib_module):
Load a template tag library module.
Verifies that the library contains a 'register' attribute, and
returns that attribute as the representation of the library
mod = import_module(taglib_module)
except ImportError as e:
# If the ImportError is because the taglib submodule does not exist,
# that's not an error that should be raised. If the submodule exists
# and raised an ImportError on the attempt to load it, that we want
# to raise.
if is_library_missing(taglib_module):
return None
raise InvalidTemplateLibrary("ImportError raised loading %s: %s" %
(taglib_module, e))
return mod.register
except AttributeError:
raise InvalidTemplateLibrary("Template library %s does not have "
"a variable named 'register'" %
def get_templatetags_modules():
Return the list of all available template tag modules.
Caches the result for faster access.
templatetags_modules_candidates = ['django.templatetags']
'%s.templatetags' %
for app_config in apps.get_app_configs())
templatetags_modules = []
for templatetag_module in templatetags_modules_candidates:
except ImportError:
return templatetags_modules
def get_library(library_name):
Load the template library module with the given name.
If library is not already loaded loop over all templatetags modules
to locate it.
{% load somelib %} and {% load someotherlib %} loops twice.
Subsequent loads eg. {% load somelib %} in the same process will grab
the cached module from libraries.
lib = libraries.get(library_name, None)
if not lib:
templatetags_modules = get_templatetags_modules()
tried_modules = []
for module in templatetags_modules:
taglib_module = '%s.%s' % (module, library_name)
lib = import_library(taglib_module)
if lib:
libraries[library_name] = lib
if not lib:
raise InvalidTemplateLibrary("Template library %s not found, "
"tried %s" %
return lib
def add_to_builtins(module):
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