blob: f9d7a6806caf54996c05f2e108883d380eeec923 [file] [log] [blame]
# -*- coding: utf-8 -*-
Runtime helpers.
:copyright: (c) 2017 by the Jinja Team.
:license: BSD.
import sys
from itertools import chain
from types import MethodType
from jinja2.nodes import EvalContext, _context_function_types
from jinja2.utils import Markup, soft_unicode, escape, missing, concat, \
internalcode, object_type_repr, evalcontextfunction, Namespace
from jinja2.exceptions import UndefinedError, TemplateRuntimeError, \
from jinja2._compat import imap, text_type, iteritems, \
implements_iterator, implements_to_string, string_types, PY2, \
# these variables are exported to the template runtime
__all__ = ['LoopContext', 'TemplateReference', 'Macro', 'Markup',
'TemplateRuntimeError', 'missing', 'concat', 'escape',
'markup_join', 'unicode_join', 'to_string', 'identity',
'TemplateNotFound', 'Namespace']
#: the name of the function that is used to convert something into
#: a string. We can just use the text type here.
to_string = text_type
#: the identity function. Useful for certain things in the environment
identity = lambda x: x
_first_iteration = object()
_last_iteration = object()
def markup_join(seq):
"""Concatenation that escapes if necessary and converts to unicode."""
buf = []
iterator = imap(soft_unicode, seq)
for arg in iterator:
if hasattr(arg, '__html__'):
return Markup(u'').join(chain(buf, iterator))
return concat(buf)
def unicode_join(seq):
"""Simple args to unicode conversion and concatenation."""
return concat(imap(text_type, seq))
def new_context(environment, template_name, blocks, vars=None,
shared=None, globals=None, locals=None):
"""Internal helper to for context creation."""
if vars is None:
vars = {}
if shared:
parent = vars
parent = dict(globals or (), **vars)
if locals:
# if the parent is shared a copy should be created because
# we don't want to modify the dict passed
if shared:
parent = dict(parent)
for key, value in iteritems(locals):
if value is not missing:
parent[key] = value
return environment.context_class(environment, parent, template_name,
class TemplateReference(object):
"""The `self` in templates."""
def __init__(self, context):
self.__context = context
def __getitem__(self, name):
blocks = self.__context.blocks[name]
return BlockReference(name, self.__context, blocks, 0)
def __repr__(self):
return '<%s %r>' % (
def _get_func(x):
return getattr(x, '__func__', x)
class ContextMeta(type):
def __new__(cls, name, bases, d):
rv = type.__new__(cls, name, bases, d)
if bases == ():
return rv
resolve = _get_func(rv.resolve)
default_resolve = _get_func(Context.resolve)
resolve_or_missing = _get_func(rv.resolve_or_missing)
default_resolve_or_missing = _get_func(Context.resolve_or_missing)
# If we have a changed resolve but no changed default or missing
# resolve we invert the call logic.
if resolve is not default_resolve and \
resolve_or_missing is default_resolve_or_missing:
rv._legacy_resolve_mode = True
elif resolve is default_resolve and \
resolve_or_missing is default_resolve_or_missing:
rv._fast_resolve_mode = True
return rv
def resolve_or_missing(context, key, missing=missing):
if key in context.vars:
return context.vars[key]
if key in context.parent:
return context.parent[key]
return missing
class Context(with_metaclass(ContextMeta)):
"""The template context holds the variables of a template. It stores the
values passed to the template and also the names the template exports.
Creating instances is neither supported nor useful as it's created
automatically at various stages of the template evaluation and should not
be created by hand.
The context is immutable. Modifications on :attr:`parent` **must not**
happen and modifications on :attr:`vars` are allowed from generated
template code only. Template filters and global functions marked as
:func:`contextfunction`\\s get the active context passed as first argument
and are allowed to access the context read-only.
The template context supports read only dict operations (`get`,
`keys`, `values`, `items`, `iterkeys`, `itervalues`, `iteritems`,
`__getitem__`, `__contains__`). Additionally there is a :meth:`resolve`
method that doesn't fail with a `KeyError` but returns an
:class:`Undefined` object for missing variables.
# XXX: we want to eventually make this be a deprecation warning and
# remove it.
_legacy_resolve_mode = False
_fast_resolve_mode = False
def __init__(self, environment, parent, name, blocks):
self.parent = parent
self.vars = {}
self.environment = environment
self.eval_ctx = EvalContext(self.environment, name)
self.exported_vars = set() = name
# create the initial mapping of blocks. Whenever template inheritance
# takes place the runtime will update this mapping with the new blocks
# from the template.
self.blocks = dict((k, [v]) for k, v in iteritems(blocks))
# In case we detect the fast resolve mode we can set up an alias
# here that bypasses the legacy code logic.
if self._fast_resolve_mode:
self.resolve_or_missing = MethodType(resolve_or_missing, self)
def super(self, name, current):
"""Render a parent block."""
blocks = self.blocks[name]
index = blocks.index(current) + 1
except LookupError:
return self.environment.undefined('there is no parent block '
'called %r.' % name,
return BlockReference(name, self, blocks, index)
def get(self, key, default=None):
"""Returns an item from the template context, if it doesn't exist
`default` is returned.
return self[key]
except KeyError:
return default
def resolve(self, key):
"""Looks up a variable like `__getitem__` or `get` but returns an
:class:`Undefined` object with the name of the name looked up.
if self._legacy_resolve_mode:
rv = resolve_or_missing(self, key)
rv = self.resolve_or_missing(key)
if rv is missing:
return self.environment.undefined(name=key)
return rv
def resolve_or_missing(self, key):
"""Resolves a variable like :meth:`resolve` but returns the
special `missing` value if it cannot be found.
if self._legacy_resolve_mode:
rv = self.resolve(key)
if isinstance(rv, Undefined):
rv = missing
return rv
return resolve_or_missing(self, key)
def get_exported(self):
"""Get a new dict with the exported variables."""
return dict((k, self.vars[k]) for k in self.exported_vars)
def get_all(self):
"""Return the complete context as dict including the exported
variables. For optimizations reasons this might not return an
actual copy so be careful with using it.
if not self.vars:
return self.parent
if not self.parent:
return self.vars
return dict(self.parent, **self.vars)
def call(__self, __obj, *args, **kwargs):
"""Call the callable with the arguments and keyword arguments
provided but inject the active context or environment as first
argument if the callable is a :func:`contextfunction` or
if __debug__:
__traceback_hide__ = True # noqa
# Allow callable classes to take a context
if hasattr(__obj, '__call__'):
fn = __obj.__call__
for fn_type in ('contextfunction',
if hasattr(fn, fn_type):
__obj = fn
if isinstance(__obj, _context_function_types):
if getattr(__obj, 'contextfunction', 0):
args = (__self,) + args
elif getattr(__obj, 'evalcontextfunction', 0):
args = (__self.eval_ctx,) + args
elif getattr(__obj, 'environmentfunction', 0):
args = (__self.environment,) + args
return __obj(*args, **kwargs)
except StopIteration:
return __self.environment.undefined('value was undefined because '
'a callable raised a '
'StopIteration exception')
def derived(self, locals=None):
"""Internal helper function to create a derived context. This is
used in situations where the system needs a new context in the same
template that is independent.
context = new_context(self.environment,, {},
self.get_all(), True, None, locals)
context.eval_ctx = self.eval_ctx
context.blocks.update((k, list(v)) for k, v in iteritems(self.blocks))
return context
def _all(meth):
proxy = lambda self: getattr(self.get_all(), meth)()
proxy.__doc__ = getattr(dict, meth).__doc__
proxy.__name__ = meth
return proxy
keys = _all('keys')
values = _all('values')
items = _all('items')
# not available on python 3
if PY2:
iterkeys = _all('iterkeys')
itervalues = _all('itervalues')
iteritems = _all('iteritems')
del _all
def __contains__(self, name):
return name in self.vars or name in self.parent
def __getitem__(self, key):
"""Lookup a variable or raise `KeyError` if the variable is
item = self.resolve_or_missing(key)
if item is missing:
raise KeyError(key)
return item
def __repr__(self):
return '<%s %s of %r>' % (
# register the context as mapping if possible
from collections import Mapping
except ImportError:
class BlockReference(object):
"""One block on a template reference."""
def __init__(self, name, context, stack, depth): = name
self._context = context
self._stack = stack
self._depth = depth
def super(self):
"""Super the block."""
if self._depth + 1 >= len(self._stack):
return self._context.environment. \
undefined('there is no parent block called %r.' %, name='super')
return BlockReference(, self._context, self._stack,
self._depth + 1)
def __call__(self):
rv = concat(self._stack[self._depth](self._context))
if self._context.eval_ctx.autoescape:
rv = Markup(rv)
return rv
class LoopContextBase(object):
"""A loop context for dynamic iteration."""
_before = _first_iteration
_current = _first_iteration
_after = _last_iteration
_length = None
def __init__(self, undefined, recurse=None, depth0=0):
self._undefined = undefined
self._recurse = recurse
self.index0 = -1
self.depth0 = depth0
self._last_checked_value = missing
def cycle(self, *args):
"""Cycles among the arguments with the current loop index."""
if not args:
raise TypeError('no items for cycling given')
return args[self.index0 % len(args)]
def changed(self, *value):
"""Checks whether the value has changed since the last call."""
if self._last_checked_value != value:
self._last_checked_value = value
return True
return False
first = property(lambda x: x.index0 == 0)
last = property(lambda x: x._after is _last_iteration)
index = property(lambda x: x.index0 + 1)
revindex = property(lambda x: x.length - x.index0)
revindex0 = property(lambda x: x.length - x.index)
depth = property(lambda x: x.depth0 + 1)
def previtem(self):
if self._before is _first_iteration:
return self._undefined('there is no previous item')
return self._before
def nextitem(self):
if self._after is _last_iteration:
return self._undefined('there is no next item')
return self._after
def __len__(self):
return self.length
def loop(self, iterable):
if self._recurse is None:
raise TypeError('Tried to call non recursive loop. Maybe you '
"forgot the 'recursive' modifier.")
return self._recurse(iterable, self._recurse, self.depth0 + 1)
# a nifty trick to enhance the error message if someone tried to call
# the the loop without or with too many arguments.
__call__ = loop
del loop
def __repr__(self):
return '<%s %r/%r>' % (
class LoopContext(LoopContextBase):
def __init__(self, iterable, undefined, recurse=None, depth0=0):
LoopContextBase.__init__(self, undefined, recurse, depth0)
self._iterator = iter(iterable)
# try to get the length of the iterable early. This must be done
# here because there are some broken iterators around where there
# __len__ is the number of iterations left (i'm looking at your
# listreverseiterator!).
self._length = len(iterable)
except (TypeError, AttributeError):
self._length = None
self._after = self._safe_next()
def length(self):
if self._length is None:
# if was not possible to get the length of the iterator when
# the loop context was created (ie: iterating over a generator)
# we have to convert the iterable into a sequence and use the
# length of that + the number of iterations so far.
iterable = tuple(self._iterator)
self._iterator = iter(iterable)
iterations_done = self.index0 + 2
self._length = len(iterable) + iterations_done
return self._length
def __iter__(self):
return LoopContextIterator(self)
def _safe_next(self):
return next(self._iterator)
except StopIteration:
return _last_iteration
class LoopContextIterator(object):
"""The iterator for a loop context."""
__slots__ = ('context',)
def __init__(self, context):
self.context = context
def __iter__(self):
return self
def __next__(self):
ctx = self.context
ctx.index0 += 1
if ctx._after is _last_iteration:
raise StopIteration()
ctx._before = ctx._current
ctx._current = ctx._after
ctx._after = ctx._safe_next()
return ctx._current, ctx
class Macro(object):
"""Wraps a macro function."""
def __init__(self, environment, func, name, arguments,
catch_kwargs, catch_varargs, caller,
self._environment = environment
self._func = func
self._argument_count = len(arguments) = name
self.arguments = arguments
self.catch_kwargs = catch_kwargs
self.catch_varargs = catch_varargs
self.caller = caller
self.explicit_caller = 'caller' in arguments
if default_autoescape is None:
default_autoescape = environment.autoescape
self._default_autoescape = default_autoescape
def __call__(self, *args, **kwargs):
# This requires a bit of explanation, In the past we used to
# decide largely based on compile-time information if a macro is
# safe or unsafe. While there was a volatile mode it was largely
# unused for deciding on escaping. This turns out to be
# problemtic for macros because if a macro is safe or not not so
# much depends on the escape mode when it was defined but when it
# was used.
# Because however we export macros from the module system and
# there are historic callers that do not pass an eval context (and
# will continue to not pass one), we need to perform an instance
# check here.
# This is considered safe because an eval context is not a valid
# argument to callables otherwise anwyays. Worst case here is
# that if no eval context is passed we fall back to the compile
# time autoescape flag.
if args and isinstance(args[0], EvalContext):
autoescape = args[0].autoescape
args = args[1:]
autoescape = self._default_autoescape
# try to consume the positional arguments
arguments = list(args[:self._argument_count])
off = len(arguments)
# For information why this is necessary refer to the handling
# of caller in the `macro_body` handler in the compiler.
found_caller = False
# if the number of arguments consumed is not the number of
# arguments expected we start filling in keyword arguments
# and defaults.
if off != self._argument_count:
for idx, name in enumerate(self.arguments[len(arguments):]):
value = kwargs.pop(name)
except KeyError:
value = missing
if name == 'caller':
found_caller = True
found_caller = self.explicit_caller
# it's important that the order of these arguments does not change
# if not also changed in the compiler's `function_scoping` method.
# the order is caller, keyword arguments, positional arguments!
if self.caller and not found_caller:
caller = kwargs.pop('caller', None)
if caller is None:
caller = self._environment.undefined('No caller defined',
if self.catch_kwargs:
elif kwargs:
if 'caller' in kwargs:
raise TypeError('macro %r was invoked with two values for '
'the special caller argument. This is '
'most likely a bug.' %
raise TypeError('macro %r takes no keyword argument %r' %
(, next(iter(kwargs))))
if self.catch_varargs:
elif len(args) > self._argument_count:
raise TypeError('macro %r takes not more than %d argument(s)' %
(, len(self.arguments)))
return self._invoke(arguments, autoescape)
def _invoke(self, arguments, autoescape):
"""This method is being swapped out by the async implementation."""
rv = self._func(*arguments)
if autoescape:
rv = Markup(rv)
return rv
def __repr__(self):
return '<%s %s>' % (
self.__class__.__name__, is None and 'anonymous' or repr(
class Undefined(object):
"""The default undefined type. This undefined type can be printed and
iterated over, but every other access will raise an :exc:`jinja2.exceptions.UndefinedError`:
>>> foo = Undefined(name='foo')
>>> str(foo)
>>> not foo
>>> foo + 42
Traceback (most recent call last):
jinja2.exceptions.UndefinedError: 'foo' is undefined
__slots__ = ('_undefined_hint', '_undefined_obj', '_undefined_name',
def __init__(self, hint=None, obj=missing, name=None, exc=UndefinedError):
self._undefined_hint = hint
self._undefined_obj = obj
self._undefined_name = name
self._undefined_exception = exc
def _fail_with_undefined_error(self, *args, **kwargs):
"""Regular callback function for undefined objects that raises an
`jinja2.exceptions.UndefinedError` on call.
if self._undefined_hint is None:
if self._undefined_obj is missing:
hint = '%r is undefined' % self._undefined_name
elif not isinstance(self._undefined_name, string_types):
hint = '%s has no element %r' % (
hint = '%r has no attribute %r' % (
hint = self._undefined_hint
raise self._undefined_exception(hint)
def __getattr__(self, name):
if name[:2] == '__':
raise AttributeError(name)
return self._fail_with_undefined_error()
__add__ = __radd__ = __mul__ = __rmul__ = __div__ = __rdiv__ = \
__truediv__ = __rtruediv__ = __floordiv__ = __rfloordiv__ = \
__mod__ = __rmod__ = __pos__ = __neg__ = __call__ = \
__getitem__ = __lt__ = __le__ = __gt__ = __ge__ = __int__ = \
__float__ = __complex__ = __pow__ = __rpow__ = __sub__ = \
__rsub__ = _fail_with_undefined_error
def __eq__(self, other):
return type(self) is type(other)
def __ne__(self, other):
return not self.__eq__(other)
def __hash__(self):
return id(type(self))
def __str__(self):
return u''
def __len__(self):
return 0
def __iter__(self):
if 0:
yield None
def __nonzero__(self):
return False
__bool__ = __nonzero__
def __repr__(self):
return 'Undefined'
def make_logging_undefined(logger=None, base=None):
"""Given a logger object this returns a new undefined class that will
log certain failures. It will log iterations and printing. If no
logger is given a default logger is created.
logger = logging.getLogger(__name__)
LoggingUndefined = make_logging_undefined(
.. versionadded:: 2.8
:param logger: the logger to use. If not provided, a default logger
is created.
:param base: the base class to add logging functionality to. This
defaults to :class:`Undefined`.
if logger is None:
import logging
logger = logging.getLogger(__name__)
if base is None:
base = Undefined
def _log_message(undef):
if undef._undefined_hint is None:
if undef._undefined_obj is missing:
hint = '%s is undefined' % undef._undefined_name
elif not isinstance(undef._undefined_name, string_types):
hint = '%s has no element %s' % (
hint = '%s has no attribute %s' % (
hint = undef._undefined_hint
logger.warning('Template variable warning: %s', hint)
class LoggingUndefined(base):
def _fail_with_undefined_error(self, *args, **kwargs):
return base._fail_with_undefined_error(self, *args, **kwargs)
except self._undefined_exception as e:
logger.error('Template variable error: %s', str(e))
raise e
def __str__(self):
rv = base.__str__(self)
return rv
def __iter__(self):
rv = base.__iter__(self)
return rv
if PY2:
def __nonzero__(self):
rv = base.__nonzero__(self)
return rv
def __unicode__(self):
rv = base.__unicode__(self)
return rv
def __bool__(self):
rv = base.__bool__(self)
return rv
return LoggingUndefined
class DebugUndefined(Undefined):
"""An undefined that returns the debug info when printed.
>>> foo = DebugUndefined(name='foo')
>>> str(foo)
'{{ foo }}'
>>> not foo
>>> foo + 42
Traceback (most recent call last):
jinja2.exceptions.UndefinedError: 'foo' is undefined
__slots__ = ()
def __str__(self):
if self._undefined_hint is None:
if self._undefined_obj is missing:
return u'{{ %s }}' % self._undefined_name
return '{{ no such element: %s[%r] }}' % (
return u'{{ undefined value printed: %s }}' % self._undefined_hint
class StrictUndefined(Undefined):
"""An undefined that barks on print and iteration as well as boolean
tests and all kinds of comparisons. In other words: you can do nothing
with it except checking if it's defined using the `defined` test.
>>> foo = StrictUndefined(name='foo')
>>> str(foo)
Traceback (most recent call last):
jinja2.exceptions.UndefinedError: 'foo' is undefined
>>> not foo
Traceback (most recent call last):
jinja2.exceptions.UndefinedError: 'foo' is undefined
>>> foo + 42
Traceback (most recent call last):
jinja2.exceptions.UndefinedError: 'foo' is undefined
__slots__ = ()
__iter__ = __str__ = __len__ = __nonzero__ = __eq__ = \
__ne__ = __bool__ = __hash__ = \
# remove remaining slots attributes, after the metaclass did the magic they
# are unneeded and irritating as they contain wrong data for the subclasses.
del Undefined.__slots__, DebugUndefined.__slots__, StrictUndefined.__slots__