mirror of
https://github.com/django/django.git
synced 2025-11-04 13:39:16 +00:00
427 lines
14 KiB
Python
427 lines
14 KiB
Python
import copy
|
|
import operator
|
|
import warnings
|
|
from functools import total_ordering, wraps
|
|
|
|
from django.utils import six
|
|
from django.utils.deprecation import RemovedInDjango20Warning
|
|
|
|
|
|
# You can't trivially replace this with `functools.partial` because this binds
|
|
# to classes and returns bound instances, whereas functools.partial (on
|
|
# CPython) is a type and its instances don't bind.
|
|
def curry(_curried_func, *args, **kwargs):
|
|
def _curried(*moreargs, **morekwargs):
|
|
return _curried_func(*(args + moreargs), **dict(kwargs, **morekwargs))
|
|
return _curried
|
|
|
|
|
|
class cached_property(object):
|
|
"""
|
|
Decorator that converts a method with a single self argument into a
|
|
property cached on the instance.
|
|
|
|
Optional ``name`` argument allows you to make cached properties of other
|
|
methods. (e.g. url = cached_property(get_absolute_url, name='url') )
|
|
"""
|
|
def __init__(self, func, name=None):
|
|
self.func = func
|
|
self.__doc__ = getattr(func, '__doc__')
|
|
self.name = name or func.__name__
|
|
|
|
def __get__(self, instance, cls=None):
|
|
if instance is None:
|
|
return self
|
|
res = instance.__dict__[self.name] = self.func(instance)
|
|
return res
|
|
|
|
|
|
class Promise(object):
|
|
"""
|
|
This is just a base class for the proxy class created in
|
|
the closure of the lazy function. It can be used to recognize
|
|
promises in code.
|
|
"""
|
|
pass
|
|
|
|
|
|
def lazy(func, *resultclasses):
|
|
"""
|
|
Turns any callable into a lazy evaluated callable. You need to give result
|
|
classes or types -- at least one is needed so that the automatic forcing of
|
|
the lazy evaluation code is triggered. Results are not memoized; the
|
|
function is evaluated on every access.
|
|
"""
|
|
|
|
@total_ordering
|
|
class __proxy__(Promise):
|
|
"""
|
|
Encapsulate a function call and act as a proxy for methods that are
|
|
called on the result of that function. The function is not evaluated
|
|
until one of the methods on the result is called.
|
|
"""
|
|
__prepared = False
|
|
|
|
def __init__(self, args, kw):
|
|
self.__args = args
|
|
self.__kw = kw
|
|
if not self.__prepared:
|
|
self.__prepare_class__()
|
|
self.__prepared = True
|
|
|
|
def __reduce__(self):
|
|
return (
|
|
_lazy_proxy_unpickle,
|
|
(func, self.__args, self.__kw) + resultclasses
|
|
)
|
|
|
|
def __repr__(self):
|
|
return repr(self.__cast())
|
|
|
|
@classmethod
|
|
def __prepare_class__(cls):
|
|
for resultclass in resultclasses:
|
|
for type_ in resultclass.mro():
|
|
for method_name in type_.__dict__.keys():
|
|
# All __promise__ return the same wrapper method, they
|
|
# look up the correct implementation when called.
|
|
if hasattr(cls, method_name):
|
|
continue
|
|
meth = cls.__promise__(method_name)
|
|
setattr(cls, method_name, meth)
|
|
cls._delegate_bytes = bytes in resultclasses
|
|
cls._delegate_text = six.text_type in resultclasses
|
|
assert not (cls._delegate_bytes and cls._delegate_text), (
|
|
"Cannot call lazy() with both bytes and text return types.")
|
|
if cls._delegate_text:
|
|
if six.PY3:
|
|
cls.__str__ = cls.__text_cast
|
|
else:
|
|
cls.__unicode__ = cls.__text_cast
|
|
cls.__str__ = cls.__bytes_cast_encoded
|
|
elif cls._delegate_bytes:
|
|
if six.PY3:
|
|
cls.__bytes__ = cls.__bytes_cast
|
|
else:
|
|
cls.__str__ = cls.__bytes_cast
|
|
|
|
@classmethod
|
|
def __promise__(cls, method_name):
|
|
# Builds a wrapper around some magic method
|
|
def __wrapper__(self, *args, **kw):
|
|
# Automatically triggers the evaluation of a lazy value and
|
|
# applies the given magic method of the result type.
|
|
res = func(*self.__args, **self.__kw)
|
|
return getattr(res, method_name)(*args, **kw)
|
|
return __wrapper__
|
|
|
|
def __text_cast(self):
|
|
return func(*self.__args, **self.__kw)
|
|
|
|
def __bytes_cast(self):
|
|
return bytes(func(*self.__args, **self.__kw))
|
|
|
|
def __bytes_cast_encoded(self):
|
|
return func(*self.__args, **self.__kw).encode('utf-8')
|
|
|
|
def __cast(self):
|
|
if self._delegate_bytes:
|
|
return self.__bytes_cast()
|
|
elif self._delegate_text:
|
|
return self.__text_cast()
|
|
else:
|
|
return func(*self.__args, **self.__kw)
|
|
|
|
def __str__(self):
|
|
# object defines __str__(), so __prepare_class__() won't overload
|
|
# a __str__() method from the proxied class.
|
|
return str(self.__cast())
|
|
|
|
def __ne__(self, other):
|
|
if isinstance(other, Promise):
|
|
other = other.__cast()
|
|
return self.__cast() != other
|
|
|
|
def __eq__(self, other):
|
|
if isinstance(other, Promise):
|
|
other = other.__cast()
|
|
return self.__cast() == other
|
|
|
|
def __lt__(self, other):
|
|
if isinstance(other, Promise):
|
|
other = other.__cast()
|
|
return self.__cast() < other
|
|
|
|
def __hash__(self):
|
|
return hash(self.__cast())
|
|
|
|
def __mod__(self, rhs):
|
|
if self._delegate_bytes and six.PY2:
|
|
return bytes(self) % rhs
|
|
elif self._delegate_text:
|
|
return six.text_type(self) % rhs
|
|
return self.__cast() % rhs
|
|
|
|
def __deepcopy__(self, memo):
|
|
# Instances of this class are effectively immutable. It's just a
|
|
# collection of functions. So we don't need to do anything
|
|
# complicated for copying.
|
|
memo[id(self)] = self
|
|
return self
|
|
|
|
@wraps(func)
|
|
def __wrapper__(*args, **kw):
|
|
# Creates the proxy object, instead of the actual value.
|
|
return __proxy__(args, kw)
|
|
|
|
return __wrapper__
|
|
|
|
|
|
def _lazy_proxy_unpickle(func, args, kwargs, *resultclasses):
|
|
return lazy(func, *resultclasses)(*args, **kwargs)
|
|
|
|
|
|
def lazystr(text):
|
|
"""
|
|
Shortcut for the common case of a lazy callable that returns str.
|
|
"""
|
|
from django.utils.encoding import force_text # Avoid circular import
|
|
return lazy(force_text, six.text_type)(text)
|
|
|
|
|
|
def allow_lazy(func, *resultclasses):
|
|
warnings.warn(
|
|
"django.utils.functional.allow_lazy() is deprecated in favor of "
|
|
"django.utils.functional.keep_lazy()",
|
|
RemovedInDjango20Warning, 2)
|
|
return keep_lazy(*resultclasses)(func)
|
|
|
|
|
|
def keep_lazy(*resultclasses):
|
|
"""
|
|
A decorator that allows a function to be called with one or more lazy
|
|
arguments. If none of the args are lazy, the function is evaluated
|
|
immediately, otherwise a __proxy__ is returned that will evaluate the
|
|
function when needed.
|
|
"""
|
|
if not resultclasses:
|
|
raise TypeError("You must pass at least one argument to keep_lazy().")
|
|
|
|
def decorator(func):
|
|
lazy_func = lazy(func, *resultclasses)
|
|
|
|
@wraps(func)
|
|
def wrapper(*args, **kwargs):
|
|
for arg in list(args) + list(six.itervalues(kwargs)):
|
|
if isinstance(arg, Promise):
|
|
break
|
|
else:
|
|
return func(*args, **kwargs)
|
|
return lazy_func(*args, **kwargs)
|
|
return wrapper
|
|
return decorator
|
|
|
|
|
|
def keep_lazy_text(func):
|
|
"""
|
|
A decorator for functions that accept lazy arguments and return text.
|
|
"""
|
|
return keep_lazy(six.text_type)(func)
|
|
|
|
|
|
empty = object()
|
|
|
|
|
|
def new_method_proxy(func):
|
|
def inner(self, *args):
|
|
if self._wrapped is empty:
|
|
self._setup()
|
|
return func(self._wrapped, *args)
|
|
return inner
|
|
|
|
|
|
class LazyObject(object):
|
|
"""
|
|
A wrapper for another class that can be used to delay instantiation of the
|
|
wrapped class.
|
|
|
|
By subclassing, you have the opportunity to intercept and alter the
|
|
instantiation. If you don't need to do that, use SimpleLazyObject.
|
|
"""
|
|
|
|
# Avoid infinite recursion when tracing __init__ (#19456).
|
|
_wrapped = None
|
|
|
|
def __init__(self):
|
|
# Note: if a subclass overrides __init__(), it will likely need to
|
|
# override __copy__() and __deepcopy__() as well.
|
|
self._wrapped = empty
|
|
|
|
__getattr__ = new_method_proxy(getattr)
|
|
|
|
def __setattr__(self, name, value):
|
|
if name == "_wrapped":
|
|
# Assign to __dict__ to avoid infinite __setattr__ loops.
|
|
self.__dict__["_wrapped"] = value
|
|
else:
|
|
if self._wrapped is empty:
|
|
self._setup()
|
|
setattr(self._wrapped, name, value)
|
|
|
|
def __delattr__(self, name):
|
|
if name == "_wrapped":
|
|
raise TypeError("can't delete _wrapped.")
|
|
if self._wrapped is empty:
|
|
self._setup()
|
|
delattr(self._wrapped, name)
|
|
|
|
def _setup(self):
|
|
"""
|
|
Must be implemented by subclasses to initialize the wrapped object.
|
|
"""
|
|
raise NotImplementedError('subclasses of LazyObject must provide a _setup() method')
|
|
|
|
# Because we have messed with __class__ below, we confuse pickle as to what
|
|
# class we are pickling. We're going to have to initialize the wrapped
|
|
# object to successfully pickle it, so we might as well just pickle the
|
|
# wrapped object since they're supposed to act the same way.
|
|
#
|
|
# Unfortunately, if we try to simply act like the wrapped object, the ruse
|
|
# will break down when pickle gets our id(). Thus we end up with pickle
|
|
# thinking, in effect, that we are a distinct object from the wrapped
|
|
# object, but with the same __dict__. This can cause problems (see #25389).
|
|
#
|
|
# So instead, we define our own __reduce__ method and custom unpickler. We
|
|
# pickle the wrapped object as the unpickler's argument, so that pickle
|
|
# will pickle it normally, and then the unpickler simply returns its
|
|
# argument.
|
|
def __reduce__(self):
|
|
if self._wrapped is empty:
|
|
self._setup()
|
|
return (unpickle_lazyobject, (self._wrapped,))
|
|
|
|
# Overriding __class__ stops __reduce__ from being called on Python 2.
|
|
# So, define __getstate__ in a way that cooperates with the way that
|
|
# pickle interprets this class. This fails when the wrapped class is a
|
|
# builtin, but it's better than nothing.
|
|
def __getstate__(self):
|
|
if self._wrapped is empty:
|
|
self._setup()
|
|
return self._wrapped.__dict__
|
|
|
|
def __copy__(self):
|
|
if self._wrapped is empty:
|
|
# If uninitialized, copy the wrapper. Use type(self), not
|
|
# self.__class__, because the latter is proxied.
|
|
return type(self)()
|
|
else:
|
|
# If initialized, return a copy of the wrapped object.
|
|
return copy.copy(self._wrapped)
|
|
|
|
def __deepcopy__(self, memo):
|
|
if self._wrapped is empty:
|
|
# We have to use type(self), not self.__class__, because the
|
|
# latter is proxied.
|
|
result = type(self)()
|
|
memo[id(self)] = result
|
|
return result
|
|
return copy.deepcopy(self._wrapped, memo)
|
|
|
|
if six.PY3:
|
|
__bytes__ = new_method_proxy(bytes)
|
|
__str__ = new_method_proxy(str)
|
|
__bool__ = new_method_proxy(bool)
|
|
else:
|
|
__str__ = new_method_proxy(str)
|
|
__unicode__ = new_method_proxy(unicode) # NOQA: unicode undefined on PY3
|
|
__nonzero__ = new_method_proxy(bool)
|
|
|
|
# Introspection support
|
|
__dir__ = new_method_proxy(dir)
|
|
|
|
# Need to pretend to be the wrapped class, for the sake of objects that
|
|
# care about this (especially in equality tests)
|
|
__class__ = property(new_method_proxy(operator.attrgetter("__class__")))
|
|
__eq__ = new_method_proxy(operator.eq)
|
|
__ne__ = new_method_proxy(operator.ne)
|
|
__hash__ = new_method_proxy(hash)
|
|
|
|
# List/Tuple/Dictionary methods support
|
|
__getitem__ = new_method_proxy(operator.getitem)
|
|
__setitem__ = new_method_proxy(operator.setitem)
|
|
__delitem__ = new_method_proxy(operator.delitem)
|
|
__iter__ = new_method_proxy(iter)
|
|
__len__ = new_method_proxy(len)
|
|
__contains__ = new_method_proxy(operator.contains)
|
|
|
|
|
|
def unpickle_lazyobject(wrapped):
|
|
"""
|
|
Used to unpickle lazy objects. Just return its argument, which will be the
|
|
wrapped object.
|
|
"""
|
|
return wrapped
|
|
|
|
|
|
class SimpleLazyObject(LazyObject):
|
|
"""
|
|
A lazy object initialized from any function.
|
|
|
|
Designed for compound objects of unknown type. For builtins or objects of
|
|
known type, use django.utils.functional.lazy.
|
|
"""
|
|
def __init__(self, func):
|
|
"""
|
|
Pass in a callable that returns the object to be wrapped.
|
|
|
|
If copies are made of the resulting SimpleLazyObject, which can happen
|
|
in various circumstances within Django, then you must ensure that the
|
|
callable can be safely run more than once and will return the same
|
|
value.
|
|
"""
|
|
self.__dict__['_setupfunc'] = func
|
|
super(SimpleLazyObject, self).__init__()
|
|
|
|
def _setup(self):
|
|
self._wrapped = self._setupfunc()
|
|
|
|
# Return a meaningful representation of the lazy object for debugging
|
|
# without evaluating the wrapped object.
|
|
def __repr__(self):
|
|
if self._wrapped is empty:
|
|
repr_attr = self._setupfunc
|
|
else:
|
|
repr_attr = self._wrapped
|
|
return '<%s: %r>' % (type(self).__name__, repr_attr)
|
|
|
|
def __copy__(self):
|
|
if self._wrapped is empty:
|
|
# If uninitialized, copy the wrapper. Use SimpleLazyObject, not
|
|
# self.__class__, because the latter is proxied.
|
|
return SimpleLazyObject(self._setupfunc)
|
|
else:
|
|
# If initialized, return a copy of the wrapped object.
|
|
return copy.copy(self._wrapped)
|
|
|
|
def __deepcopy__(self, memo):
|
|
if self._wrapped is empty:
|
|
# We have to use SimpleLazyObject, not self.__class__, because the
|
|
# latter is proxied.
|
|
result = SimpleLazyObject(self._setupfunc)
|
|
memo[id(self)] = result
|
|
return result
|
|
return copy.deepcopy(self._wrapped, memo)
|
|
|
|
|
|
def partition(predicate, values):
|
|
"""
|
|
Splits the values into two sets, based on the return value of the function
|
|
(True/False). e.g.:
|
|
|
|
>>> partition(lambda x: x > 3, range(5))
|
|
[0, 1, 2, 3], [4]
|
|
"""
|
|
results = ([], [])
|
|
for item in values:
|
|
results[predicate(item)].append(item)
|
|
return results
|