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Source code for django.template.base

"""
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.

Usage:

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)
u'<html><h1>Hello</h1></html>'
>>> c = template.Context({'test':False, 'varvalue': 'Hello'})
>>> t.render(c)
u'<html></html>'
"""

from __future__ import unicode_literals

import inspect
import re
import warnings
from functools import partial
from importlib import import_module

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 RemovedInDjango110Warning
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.inspect import getargspec
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

TOKEN_TEXT = 0
TOKEN_VAR = 1
TOKEN_BLOCK = 2
TOKEN_COMMENT = 3
TOKEN_MAPPING = {
    TOKEN_TEXT: 'Text',
    TOKEN_VAR: 'Var',
    TOKEN_BLOCK: 'Block',
    TOKEN_COMMENT: 'Comment',
}

# template syntax constants
FILTER_SEPARATOR = '|'
FILTER_ARGUMENT_SEPARATOR = ':'
VARIABLE_ATTRIBUTE_SEPARATOR = '.'
BLOCK_TAG_START = '{%'
BLOCK_TAG_END = '%}'
VARIABLE_TAG_START = '{{'
VARIABLE_TAG_END = '}}'
COMMENT_TAG_START = '{#'
COMMENT_TAG_END = '#}'
TRANSLATOR_COMMENT_MARK = 'Translators'
SINGLE_BRACE_START = '{'
SINGLE_BRACE_END = '}'

ALLOWED_VARIABLE_CHARS = ('abcdefghijklmnopqrstuvwxyz'
                         'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_.')

# 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(VARIABLE_TAG_START), re.escape(VARIABLE_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 = []


[docs]class TemplateSyntaxError(Exception):
pass
[docs]class TemplateDoesNotExist(Exception):
pass class TemplateEncodingError(Exception): pass @python_2_unicode_compatible 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): pass class Origin(object): def __init__(self, name): self.name = name def reload(self): raise NotImplementedError('subclasses of Origin must provide a reload() method') def __str__(self): return self.name
[docs]class StringOrigin(Origin): def __init__(self, source): super(StringOrigin, self).__init__(UNKNOWN_SOURCE) self.source = source def reload(self):
return self.source
[docs]class Template(object): def __init__(self, template_string, origin=None, name=None, engine=None): try: 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) self.name = 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)
[docs] def render(self, context): "Display stage -- can be called many times" context.render_context.push() try: if context.template is None: with context.bind_template(self): return self._render(context) else: return self._render(context) finally:
context.render_context.pop() class Token(object): def __init__(self, token_type, contents): # token_type must be TOKEN_TEXT, TOKEN_VAR, TOKEN_BLOCK or # TOKEN_COMMENT. 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) trans_bit.append(bit) bit = ' '.join(trans_bit) split.append(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) else: 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: self.add_library(lib) 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: self.empty_variable(token) try: filter_expression = self.compile_filter(token.contents) except TemplateSyntaxError as e: if not self.compile_filter_error(token, e): raise var_node = self.create_variable_node(filter_expression) self.extend_nodelist(nodelist, var_node, token) elif token.token_type == 2: # TOKEN_BLOCK try: command = token.contents.split()[0] except IndexError: self.empty_block_tag(token) if command in parse_until: # put token back on token list so calling # code knows why it terminated self.prepend_token(token) return nodelist # execute callback function for this tag and append # resulting node self.enter_command(command, token) try: compile_func = self.tags[command] except KeyError: self.invalid_block_tag(token, command, parse_until) try: compiled_result = compile_func(self, token) except TemplateSyntaxError as e: if not self.compile_function_error(token, e): raise self.extend_nodelist(nodelist, compiled_result, token) self.exit_command() if parse_until: self.unclosed_block_tag(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: return self.unclosed_block_tag([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: try: 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 nodelist.append(node) def enter_command(self, command, token): pass def exit_command(self): pass 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): pass def compile_function_error(self, token, e): pass 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): self.tags.update(lib.tags) self.filters.update(lib.filters) 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] else: 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 parser. 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 " "parsing") 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.backout.append(self.pointer) 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" % subject) 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.backout.append(self.pointer) self.pointer = i return res else: p = i i = next_space_index(subject, i) s = subject[p:i] while i < len(subject) and subject[i] in (' ', '\t'): i += 1 self.backout.append(self.pointer) 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""" (?:%(i18n_open)s%(strdq)s%(i18n_close)s| %(i18n_open)s%(strsq)s%(i18n_close)s| %(strdq)s| %(strsq)s) """ % { '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""" ^(?P<constant>%(constant)s)| ^(?P<var>[%(var_chars)s]+|%(num)s)| (?:\s*%(filter_sep)s\s* (?P<filter_name>\w+) (?:%(arg_sep)s (?: (?P<constant_arg>%(constant)s)| (?P<var_arg>[%(var_chars)s]+|%(num)s) ) )? )""" % { '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. Sample:: >>> token = 'variable|default:"Default value"|date:"Y-m-d"' >>> p = Parser('') >>> fe = FilterExpression(token, p) >>> len(fe.filters) 2 >>> 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], token[start:])) if var_obj is None: var, constant = match.group("var", "constant") if constant: try: 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) else: var_obj = Variable(var) else: filter_name = match.group("filter_name") args = [] constant_arg, var_arg = match.group("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): try: obj = self.var.resolve(context) except VariableDoesNotExist: if ignore_failures: obj = None else: 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 else: return string_if_invalid else: obj = string_if_invalid else: obj = self.var for func, args in self.filters: arg_vals = [] for lookup, arg in args: if not lookup: arg_vals.append(mark_safe(arg)) else: arg_vals.append(arg.resolve(context)) 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) else: 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) else: 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, _, _, 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", RemovedInDjango110Warning, 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 marks):: >>> c = {'article': {'section':u'News'}} >>> Variable('article.section').resolve(c) u'News' >>> 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)) try: # 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. try: 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'" % var) 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) else: # 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) else: 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() instead. """ 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)): raise 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): pass elif getattr(current, 'alters_data', False): current = context.template.engine.string_if_invalid else: try: # method call (assuming no args required) current = current() except TypeError: try: inspect.getcallargs(current) except TypeError: # arguments *were* required current = context.template.engine.string_if_invalid # invalid method call else: raise except Exception as e: if getattr(e, 'silent_variable_failure', False): current = context.template.engine.string_if_invalid else: raise 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. """ pass 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): nodes.append(self) for attr in self.child_nodelists: nodelist = getattr(self, attr, None) if nodelist: nodes.extend(nodelist.get_nodes_by_type(nodetype)) 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) else: bit = node bits.append(force_text(bit)) 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: nodes.extend(node.get_nodes_by_type(nodetype)) 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', errors='replace') 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) else: 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): try: 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 list. 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 match.group(1) 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 match.group(1): return kwargs key, value = match.groups() del bits[:1] else: 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, include_tag and assignment_tag), in particular by detecting syntax errors and by extracting positional and keyword arguments. """ if takes_context: if params[0] == 'context': params = params[1:] else: 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)) else: # 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. unhandled_params.remove(param) else: if kwargs: raise TemplateSyntaxError( "'%s' received some positional argument(s) after some " "keyword argument(s)" % name) else: # Record the positional argument args.append(parser.compile_filter(bit)) try: # Consume from the list of expected positional arguments unhandled_params.pop(0) except IndexError: if varargs is None: raise TemplateSyntaxError( "'%s' received too many positional arguments" % name) 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, InclusionNode and AssignmentNode. Manages the positional and keyword arguments to be passed to the decorated function. """ 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) else: # @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 else: 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) else: # @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 else: 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 render(self, context): resolved_args, resolved_kwargs = self.get_resolved_arguments(context) return func(*resolved_args, **resolved_kwargs) 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=SimpleNode) 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) else: raise TemplateSyntaxError("Invalid arguments provided to simple_tag") def assignment_tag(self, func=None, takes_context=None, name=None): def dec(func): params, varargs, varkw, defaults = getargspec(func) class AssignmentNode(TagHelperNode): def __init__(self, takes_context, args, kwargs, target_var): super(AssignmentNode, self).__init__(takes_context, args, kwargs) self.target_var = target_var def render(self, context): resolved_args, resolved_kwargs = self.get_resolved_arguments(context) context[self.target_var] = func(*resolved_args, **resolved_kwargs) return '' function_name = (name or getattr(func, '_decorated_function', func).__name__) def compile_func(parser, token): bits = token.split_contents()[1:] if len(bits) < 2 or bits[-2] != 'as': raise TemplateSyntaxError( "'%s' tag takes at least 2 arguments and the " "second last argument must be 'as'" % function_name) target_var = bits[-1] bits = bits[:-2] args, kwargs = parse_bits(parser, bits, params, varargs, varkw, defaults, takes_context, function_name) return AssignmentNode(takes_context, args, kwargs, target_var) compile_func.__doc__ = func.__doc__ self.tag(function_name, compile_func) return func if func is None: # @register.assignment_tag(...) return dec elif callable(func): # @register.assignment_tag return dec(func) else: raise TemplateSyntaxError("Invalid arguments provided to assignment_tag") 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): """ Renders the specified template and context. Caches the template object in render_context to avoid reparsing and loading when used in a for loop. """ resolved_args, resolved_kwargs = self.get_resolved_arguments(context) _dict = func(*resolved_args, **resolved_kwargs) t = context.render_context.get(self) if t is None: 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) else: t = context.template.engine.get_template(file_name) context.render_context[self] = t new_context = context.new(_dict) # 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 t.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/module.py. """ # Don't bother to check if '.' is in name since any name will be prefixed # with some template root. path, module = name.rsplit('.', 1) try: 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 """ try: 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 else: raise InvalidTemplateLibrary("ImportError raised loading %s: %s" % (taglib_module, e)) try: return mod.register except AttributeError: raise InvalidTemplateLibrary("Template library %s does not have " "a variable named 'register'" % taglib_module) @lru_cache.lru_cache() def get_templatetags_modules(): """ Return the list of all available template tag modules. Caches the result for faster access. """ templatetags_modules_candidates = ['django.templatetags'] templatetags_modules_candidates.extend( '%s.templatetags' % app_config.name for app_config in apps.get_app_configs()) templatetags_modules = [] for templatetag_module in templatetags_modules_candidates: try: import_module(templatetag_module) except ImportError: continue else: templatetags_modules.append(templatetag_module) 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) tried_modules.append(taglib_module) lib = import_library(taglib_module) if lib: libraries[library_name] = lib break if not lib: raise InvalidTemplateLibrary("Template library %s not found, " "tried %s" % (library_name, ','.join(tried_modules))) return lib def add_to_builtins(module): builtins.append(import_library(module)) add_to_builtins('django.template.defaulttags') add_to_builtins('django.template.defaultfilters') add_to_builtins('django.template.loader_tags')
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