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2403 lines (1874 loc) · 78 KB
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import abc
from abc import abstractmethod, abstractproperty
import collections
import contextlib
import functools
import re as stdlib_re # Avoid confusion with the re we export.
import sys
import types
try:
import collections.abc as collections_abc
except ImportError:
import collections as collections_abc # Fallback for PY3.2.
if sys.version_info[:2] >= (3, 6):
import _collections_abc # Needed for private function _check_methods # noqa
try:
from types import WrapperDescriptorType, MethodWrapperType, MethodDescriptorType
except ImportError:
WrapperDescriptorType = type(object.__init__)
MethodWrapperType = type(object().__str__)
MethodDescriptorType = type(str.join)
# Please keep __all__ alphabetized within each category.
__all__ = [
# Super-special typing primitives.
'Any',
'Callable',
'ClassVar',
'Generic',
'Optional',
'Tuple',
'Type',
'TypeVar',
'Union',
# ABCs (from collections.abc).
'AbstractSet', # collections.abc.Set.
'GenericMeta', # subclass of abc.ABCMeta and a metaclass
# for 'Generic' and ABCs below.
'ByteString',
'Container',
'ContextManager',
'Hashable',
'ItemsView',
'Iterable',
'Iterator',
'KeysView',
'Mapping',
'MappingView',
'MutableMapping',
'MutableSequence',
'MutableSet',
'Sequence',
'Sized',
'ValuesView',
# The following are added depending on presence
# of their non-generic counterparts in stdlib:
# Awaitable,
# AsyncIterator,
# AsyncIterable,
# Coroutine,
# Collection,
# AsyncGenerator,
# AsyncContextManager
# Structural checks, a.k.a. protocols.
'Reversible',
'SupportsAbs',
'SupportsBytes',
'SupportsComplex',
'SupportsFloat',
'SupportsInt',
'SupportsRound',
# Concrete collection types.
'Counter',
'Deque',
'Dict',
'DefaultDict',
'List',
'Set',
'FrozenSet',
'NamedTuple', # Not really a type.
'Generator',
# One-off things.
'AnyStr',
'cast',
'get_type_hints',
'NewType',
'no_type_check',
'no_type_check_decorator',
'overload',
'Text',
'TYPE_CHECKING',
]
# The pseudo-submodules 're' and 'io' are part of the public
# namespace, but excluded from __all__ because they might stomp on
# legitimate imports of those modules.
def _qualname(x):
if sys.version_info[:2] >= (3, 3):
return x.__qualname__
else:
# Fall back to just name.
return x.__name__
def _trim_name(nm):
whitelist = ('_TypeAlias', '_ForwardRef', '_TypingBase', '_FinalTypingBase')
if nm.startswith('_') and nm not in whitelist:
nm = nm[1:]
return nm
class TypingMeta(type):
"""Metaclass for most types defined in typing module
(not a part of public API).
This overrides __new__() to require an extra keyword parameter
'_root', which serves as a guard against naive subclassing of the
typing classes. Any legitimate class defined using a metaclass
derived from TypingMeta must pass _root=True.
This also defines a dummy constructor (all the work for most typing
constructs is done in __new__) and a nicer repr().
"""
_is_protocol = False
def __new__(cls, name, bases, namespace, *, _root=False):
if not _root:
raise TypeError("Cannot subclass %s" %
(', '.join(map(_type_repr, bases)) or '()'))
return super().__new__(cls, name, bases, namespace)
def __init__(self, *args, **kwds):
pass
def _eval_type(self, globalns, localns):
"""Override this in subclasses to interpret forward references.
For example, List['C'] is internally stored as
List[_ForwardRef('C')], which should evaluate to List[C],
where C is an object found in globalns or localns (searching
localns first, of course).
"""
return self
def _get_type_vars(self, tvars):
pass
def __repr__(self):
qname = _trim_name(_qualname(self))
return '%s.%s' % (self.__module__, qname)
class _TypingBase(metaclass=TypingMeta, _root=True):
"""Internal indicator of special typing constructs."""
__slots__ = ('__weakref__',)
def __init__(self, *args, **kwds):
pass
def __new__(cls, *args, **kwds):
"""Constructor.
This only exists to give a better error message in case
someone tries to subclass a special typing object (not a good idea).
"""
if (len(args) == 3 and
isinstance(args[0], str) and
isinstance(args[1], tuple)):
# Close enough.
raise TypeError("Cannot subclass %r" % cls)
return super().__new__(cls)
# Things that are not classes also need these.
def _eval_type(self, globalns, localns):
return self
def _get_type_vars(self, tvars):
pass
def __repr__(self):
cls = type(self)
qname = _trim_name(_qualname(cls))
return '%s.%s' % (cls.__module__, qname)
def __call__(self, *args, **kwds):
raise TypeError("Cannot instantiate %r" % type(self))
class _FinalTypingBase(_TypingBase, _root=True):
"""Internal mix-in class to prevent instantiation.
Prevents instantiation unless _root=True is given in class call.
It is used to create pseudo-singleton instances Any, Union, Optional, etc.
"""
__slots__ = ()
def __new__(cls, *args, _root=False, **kwds):
self = super().__new__(cls, *args, **kwds)
if _root is True:
return self
raise TypeError("Cannot instantiate %r" % cls)
def __reduce__(self):
return _trim_name(type(self).__name__)
class _ForwardRef(_TypingBase, _root=True):
"""Internal wrapper to hold a forward reference."""
__slots__ = ('__forward_arg__', '__forward_code__',
'__forward_evaluated__', '__forward_value__')
def __init__(self, arg):
super().__init__(arg)
if not isinstance(arg, str):
raise TypeError('Forward reference must be a string -- got %r' % (arg,))
try:
code = compile(arg, '<string>', 'eval')
except SyntaxError:
raise SyntaxError('Forward reference must be an expression -- got %r' %
(arg,))
self.__forward_arg__ = arg
self.__forward_code__ = code
self.__forward_evaluated__ = False
self.__forward_value__ = None
def _eval_type(self, globalns, localns):
if not self.__forward_evaluated__ or localns is not globalns:
if globalns is None and localns is None:
globalns = localns = {}
elif globalns is None:
globalns = localns
elif localns is None:
localns = globalns
self.__forward_value__ = _type_check(
eval(self.__forward_code__, globalns, localns),
"Forward references must evaluate to types.")
self.__forward_evaluated__ = True
return self.__forward_value__
def __eq__(self, other):
if not isinstance(other, _ForwardRef):
return NotImplemented
return (self.__forward_arg__ == other.__forward_arg__ and
self.__forward_value__ == other.__forward_value__)
def __hash__(self):
return hash((self.__forward_arg__, self.__forward_value__))
def __instancecheck__(self, obj):
raise TypeError("Forward references cannot be used with isinstance().")
def __subclasscheck__(self, cls):
raise TypeError("Forward references cannot be used with issubclass().")
def __repr__(self):
return '_ForwardRef(%r)' % (self.__forward_arg__,)
class _TypeAlias(_TypingBase, _root=True):
"""Internal helper class for defining generic variants of concrete types.
Note that this is not a type; let's call it a pseudo-type. It cannot
be used in instance and subclass checks in parameterized form, i.e.
``isinstance(42, Match[str])`` raises ``TypeError`` instead of returning
``False``.
"""
__slots__ = ('name', 'type_var', 'impl_type', 'type_checker')
def __init__(self, name, type_var, impl_type, type_checker):
"""Initializer.
Args:
name: The name, e.g. 'Pattern'.
type_var: The type parameter, e.g. AnyStr, or the
specific type, e.g. str.
impl_type: The implementation type.
type_checker: Function that takes an impl_type instance.
and returns a value that should be a type_var instance.
"""
assert isinstance(name, str), repr(name)
assert isinstance(impl_type, type), repr(impl_type)
assert not isinstance(impl_type, TypingMeta), repr(impl_type)
assert isinstance(type_var, (type, _TypingBase)), repr(type_var)
self.name = name
self.type_var = type_var
self.impl_type = impl_type
self.type_checker = type_checker
def __repr__(self):
return "%s[%s]" % (self.name, _type_repr(self.type_var))
def __getitem__(self, parameter):
if not isinstance(self.type_var, TypeVar):
raise TypeError("%s cannot be further parameterized." % self)
if self.type_var.__constraints__ and isinstance(parameter, type):
if not issubclass(parameter, self.type_var.__constraints__):
raise TypeError("%s is not a valid substitution for %s." %
(parameter, self.type_var))
if isinstance(parameter, TypeVar) and parameter is not self.type_var:
raise TypeError("%s cannot be re-parameterized." % self)
return self.__class__(self.name, parameter,
self.impl_type, self.type_checker)
def __eq__(self, other):
if not isinstance(other, _TypeAlias):
return NotImplemented
return self.name == other.name and self.type_var == other.type_var
def __hash__(self):
return hash((self.name, self.type_var))
def __instancecheck__(self, obj):
if not isinstance(self.type_var, TypeVar):
raise TypeError("Parameterized type aliases cannot be used "
"with isinstance().")
return isinstance(obj, self.impl_type)
def __subclasscheck__(self, cls):
if not isinstance(self.type_var, TypeVar):
raise TypeError("Parameterized type aliases cannot be used "
"with issubclass().")
return issubclass(cls, self.impl_type)
def _get_type_vars(types, tvars):
for t in types:
if isinstance(t, TypingMeta) or isinstance(t, _TypingBase):
t._get_type_vars(tvars)
def _type_vars(types):
tvars = []
_get_type_vars(types, tvars)
return tuple(tvars)
def _eval_type(t, globalns, localns):
if isinstance(t, TypingMeta) or isinstance(t, _TypingBase):
return t._eval_type(globalns, localns)
return t
def _type_check(arg, msg):
"""Check that the argument is a type, and return it (internal helper).
As a special case, accept None and return type(None) instead.
Also, _TypeAlias instances (e.g. Match, Pattern) are acceptable.
The msg argument is a human-readable error message, e.g.
"Union[arg, ...]: arg should be a type."
We append the repr() of the actual value (truncated to 100 chars).
"""
if arg is None:
return type(None)
if isinstance(arg, str):
arg = _ForwardRef(arg)
if (
isinstance(arg, _TypingBase) and type(arg).__name__ == '_ClassVar' or
not isinstance(arg, (type, _TypingBase)) and not callable(arg)
):
raise TypeError(msg + " Got %.100r." % (arg,))
# Bare Union etc. are not valid as type arguments
if (
type(arg).__name__ in ('_Union', '_Optional') and
not getattr(arg, '__origin__', None) or
isinstance(arg, TypingMeta) and arg._gorg in (Generic, _Protocol)
):
raise TypeError("Plain %s is not valid as type argument" % arg)
return arg
def _type_repr(obj):
"""Return the repr() of an object, special-casing types (internal helper).
If obj is a type, we return a shorter version than the default
type.__repr__, based on the module and qualified name, which is
typically enough to uniquely identify a type. For everything
else, we fall back on repr(obj).
"""
if isinstance(obj, type) and not isinstance(obj, TypingMeta):
if obj.__module__ == 'builtins':
return _qualname(obj)
return '%s.%s' % (obj.__module__, _qualname(obj))
if obj is ...:
return('...')
if isinstance(obj, types.FunctionType):
return obj.__name__
return repr(obj)
class _Any(_FinalTypingBase, _root=True):
"""Special type indicating an unconstrained type.
- Any is compatible with every type.
- Any assumed to have all methods.
- All values assumed to be instances of Any.
Note that all the above statements are true from the point of view of
static type checkers. At runtime, Any should not be used with instance
or class checks.
"""
__slots__ = ()
def __instancecheck__(self, obj):
raise TypeError("Any cannot be used with isinstance().")
def __subclasscheck__(self, cls):
raise TypeError("Any cannot be used with issubclass().")
Any = _Any(_root=True)
class _NoReturn(_FinalTypingBase, _root=True):
"""Special type indicating functions that never return.
Example::
from typing import NoReturn
def stop() -> NoReturn:
raise Exception('no way')
This type is invalid in other positions, e.g., ``List[NoReturn]``
will fail in static type checkers.
"""
__slots__ = ()
def __instancecheck__(self, obj):
raise TypeError("NoReturn cannot be used with isinstance().")
def __subclasscheck__(self, cls):
raise TypeError("NoReturn cannot be used with issubclass().")
NoReturn = _NoReturn(_root=True)
class TypeVar(_TypingBase, _root=True):
"""Type variable.
Usage::
T = TypeVar('T') # Can be anything
A = TypeVar('A', str, bytes) # Must be str or bytes
Type variables exist primarily for the benefit of static type
checkers. They serve as the parameters for generic types as well
as for generic function definitions. See class Generic for more
information on generic types. Generic functions work as follows:
def repeat(x: T, n: int) -> List[T]:
'''Return a list containing n references to x.'''
return [x]*n
def longest(x: A, y: A) -> A:
'''Return the longest of two strings.'''
return x if len(x) >= len(y) else y
The latter example's signature is essentially the overloading
of (str, str) -> str and (bytes, bytes) -> bytes. Also note
that if the arguments are instances of some subclass of str,
the return type is still plain str.
At runtime, isinstance(x, T) and issubclass(C, T) will raise TypeError.
Type variables defined with covariant=True or contravariant=True
can be used do declare covariant or contravariant generic types.
See PEP 484 for more details. By default generic types are invariant
in all type variables.
Type variables can be introspected. e.g.:
T.__name__ == 'T'
T.__constraints__ == ()
T.__covariant__ == False
T.__contravariant__ = False
A.__constraints__ == (str, bytes)
"""
__slots__ = ('__name__', '__bound__', '__constraints__',
'__covariant__', '__contravariant__')
def __init__(self, name, *constraints, bound=None,
covariant=False, contravariant=False):
super().__init__(name, *constraints, bound=bound,
covariant=covariant, contravariant=contravariant)
self.__name__ = name
if covariant and contravariant:
raise ValueError("Bivariant types are not supported.")
self.__covariant__ = bool(covariant)
self.__contravariant__ = bool(contravariant)
if constraints and bound is not None:
raise TypeError("Constraints cannot be combined with bound=...")
if constraints and len(constraints) == 1:
raise TypeError("A single constraint is not allowed")
msg = "TypeVar(name, constraint, ...): constraints must be types."
self.__constraints__ = tuple(_type_check(t, msg) for t in constraints)
if bound:
self.__bound__ = _type_check(bound, "Bound must be a type.")
else:
self.__bound__ = None
def _get_type_vars(self, tvars):
if self not in tvars:
tvars.append(self)
def __repr__(self):
if self.__covariant__:
prefix = '+'
elif self.__contravariant__:
prefix = '-'
else:
prefix = '~'
return prefix + self.__name__
def __instancecheck__(self, instance):
raise TypeError("Type variables cannot be used with isinstance().")
def __subclasscheck__(self, cls):
raise TypeError("Type variables cannot be used with issubclass().")
# Some unconstrained type variables. These are used by the container types.
# (These are not for export.)
T = TypeVar('T') # Any type.
KT = TypeVar('KT') # Key type.
VT = TypeVar('VT') # Value type.
T_co = TypeVar('T_co', covariant=True) # Any type covariant containers.
V_co = TypeVar('V_co', covariant=True) # Any type covariant containers.
VT_co = TypeVar('VT_co', covariant=True) # Value type covariant containers.
T_contra = TypeVar('T_contra', contravariant=True) # Ditto contravariant.
# A useful type variable with constraints. This represents string types.
# (This one *is* for export!)
AnyStr = TypeVar('AnyStr', bytes, str)
def _replace_arg(arg, tvars, args):
"""An internal helper function: replace arg if it is a type variable
found in tvars with corresponding substitution from args or
with corresponding substitution sub-tree if arg is a generic type.
"""
if tvars is None:
tvars = []
if hasattr(arg, '_subs_tree') and isinstance(arg, (GenericMeta, _TypingBase)):
return arg._subs_tree(tvars, args)
if isinstance(arg, TypeVar):
for i, tvar in enumerate(tvars):
if arg == tvar:
return args[i]
return arg
# Special typing constructs Union, Optional, Generic, Callable and Tuple
# use three special attributes for internal bookkeeping of generic types:
# * __parameters__ is a tuple of unique free type parameters of a generic
# type, for example, Dict[T, T].__parameters__ == (T,);
# * __origin__ keeps a reference to a type that was subscripted,
# e.g., Union[T, int].__origin__ == Union;
# * __args__ is a tuple of all arguments used in subscripting,
# e.g., Dict[T, int].__args__ == (T, int).
def _subs_tree(cls, tvars=None, args=None):
"""An internal helper function: calculate substitution tree
for generic cls after replacing its type parameters with
substitutions in tvars -> args (if any).
Repeat the same following __origin__'s.
Return a list of arguments with all possible substitutions
performed. Arguments that are generic classes themselves are represented
as tuples (so that no new classes are created by this function).
For example: _subs_tree(List[Tuple[int, T]][str]) == [(Tuple, int, str)]
"""
if cls.__origin__ is None:
return cls
# Make of chain of origins (i.e. cls -> cls.__origin__)
current = cls.__origin__
orig_chain = []
while current.__origin__ is not None:
orig_chain.append(current)
current = current.__origin__
# Replace type variables in __args__ if asked ...
tree_args = []
for arg in cls.__args__:
tree_args.append(_replace_arg(arg, tvars, args))
# ... then continue replacing down the origin chain.
for ocls in orig_chain:
new_tree_args = []
for arg in ocls.__args__:
new_tree_args.append(_replace_arg(arg, ocls.__parameters__, tree_args))
tree_args = new_tree_args
return tree_args
def _remove_dups_flatten(parameters):
"""An internal helper for Union creation and substitution: flatten Union's
among parameters, then remove duplicates and strict subclasses.
"""
# Flatten out Union[Union[...], ...].
params = []
for p in parameters:
if isinstance(p, _Union) and p.__origin__ is Union:
params.extend(p.__args__)
elif isinstance(p, tuple) and len(p) > 0 and p[0] is Union:
params.extend(p[1:])
else:
params.append(p)
# Weed out strict duplicates, preserving the first of each occurrence.
all_params = set(params)
if len(all_params) < len(params):
new_params = []
for t in params:
if t in all_params:
new_params.append(t)
all_params.remove(t)
params = new_params
assert not all_params, all_params
# Weed out subclasses.
# E.g. Union[int, Employee, Manager] == Union[int, Employee].
# If object is present it will be sole survivor among proper classes.
# Never discard type variables.
# (In particular, Union[str, AnyStr] != AnyStr.)
all_params = set(params)
for t1 in params:
if not isinstance(t1, type):
continue
if any(isinstance(t2, type) and issubclass(t1, t2)
for t2 in all_params - {t1}
if not (isinstance(t2, GenericMeta) and
t2.__origin__ is not None)):
all_params.remove(t1)
return tuple(t for t in params if t in all_params)
def _check_generic(cls, parameters):
# Check correct count for parameters of a generic cls (internal helper).
if not cls.__parameters__:
raise TypeError("%s is not a generic class" % repr(cls))
alen = len(parameters)
elen = len(cls.__parameters__)
if alen != elen:
raise TypeError("Too %s parameters for %s; actual %s, expected %s" %
("many" if alen > elen else "few", repr(cls), alen, elen))
_cleanups = []
def _tp_cache(func):
"""Internal wrapper caching __getitem__ of generic types with a fallback to
original function for non-hashable arguments.
"""
cached = functools.lru_cache()(func)
_cleanups.append(cached.cache_clear)
@functools.wraps(func)
def inner(*args, **kwds):
try:
return cached(*args, **kwds)
except TypeError:
pass # All real errors (not unhashable args) are raised below.
return func(*args, **kwds)
return inner
class _Union(_FinalTypingBase, _root=True):
"""Union type; Union[X, Y] means either X or Y.
To define a union, use e.g. Union[int, str]. Details:
- The arguments must be types and there must be at least one.
- None as an argument is a special case and is replaced by
type(None).
- Unions of unions are flattened, e.g.::
Union[Union[int, str], float] == Union[int, str, float]
- Unions of a single argument vanish, e.g.::
Union[int] == int # The constructor actually returns int
- Redundant arguments are skipped, e.g.::
Union[int, str, int] == Union[int, str]
- When comparing unions, the argument order is ignored, e.g.::
Union[int, str] == Union[str, int]
- When two arguments have a subclass relationship, the least
derived argument is kept, e.g.::
class Employee: pass
class Manager(Employee): pass
Union[int, Employee, Manager] == Union[int, Employee]
Union[Manager, int, Employee] == Union[int, Employee]
Union[Employee, Manager] == Employee
- Similar for object::
Union[int, object] == object
- You cannot subclass or instantiate a union.
- You can use Optional[X] as a shorthand for Union[X, None].
"""
__slots__ = ('__parameters__', '__args__', '__origin__', '__tree_hash__')
def __new__(cls, parameters=None, origin=None, *args, _root=False):
self = super().__new__(cls, parameters, origin, *args, _root=_root)
if origin is None:
self.__parameters__ = None
self.__args__ = None
self.__origin__ = None
self.__tree_hash__ = hash(frozenset(('Union',)))
return self
if not isinstance(parameters, tuple):
raise TypeError("Expected parameters=<tuple>")
if origin is Union:
parameters = _remove_dups_flatten(parameters)
# It's not a union if there's only one type left.
if len(parameters) == 1:
return parameters[0]
self.__parameters__ = _type_vars(parameters)
self.__args__ = parameters
self.__origin__ = origin
# Pre-calculate the __hash__ on instantiation.
# This improves speed for complex substitutions.
subs_tree = self._subs_tree()
if isinstance(subs_tree, tuple):
self.__tree_hash__ = hash(frozenset(subs_tree))
else:
self.__tree_hash__ = hash(subs_tree)
return self
def _eval_type(self, globalns, localns):
if self.__args__ is None:
return self
ev_args = tuple(_eval_type(t, globalns, localns) for t in self.__args__)
ev_origin = _eval_type(self.__origin__, globalns, localns)
if ev_args == self.__args__ and ev_origin == self.__origin__:
# Everything is already evaluated.
return self
return self.__class__(ev_args, ev_origin, _root=True)
def _get_type_vars(self, tvars):
if self.__origin__ and self.__parameters__:
_get_type_vars(self.__parameters__, tvars)
def __repr__(self):
if self.__origin__ is None:
return super().__repr__()
tree = self._subs_tree()
if not isinstance(tree, tuple):
return repr(tree)
return tree[0]._tree_repr(tree)
def _tree_repr(self, tree):
arg_list = []
for arg in tree[1:]:
if not isinstance(arg, tuple):
arg_list.append(_type_repr(arg))
else:
arg_list.append(arg[0]._tree_repr(arg))
return super().__repr__() + '[%s]' % ', '.join(arg_list)
@_tp_cache
def __getitem__(self, parameters):
if parameters == ():
raise TypeError("Cannot take a Union of no types.")
if not isinstance(parameters, tuple):
parameters = (parameters,)
if self.__origin__ is None:
msg = "Union[arg, ...]: each arg must be a type."
else:
msg = "Parameters to generic types must be types."
parameters = tuple(_type_check(p, msg) for p in parameters)
if self is not Union:
_check_generic(self, parameters)
return self.__class__(parameters, origin=self, _root=True)
def _subs_tree(self, tvars=None, args=None):
if self is Union:
return Union # Nothing to substitute
tree_args = _subs_tree(self, tvars, args)
tree_args = _remove_dups_flatten(tree_args)
if len(tree_args) == 1:
return tree_args[0] # Union of a single type is that type
return (Union,) + tree_args
def __eq__(self, other):
if isinstance(other, _Union):
return self.__tree_hash__ == other.__tree_hash__
elif self is not Union:
return self._subs_tree() == other
else:
return self is other
def __hash__(self):
return self.__tree_hash__
def __instancecheck__(self, obj):
raise TypeError("Unions cannot be used with isinstance().")
def __subclasscheck__(self, cls):
raise TypeError("Unions cannot be used with issubclass().")
Union = _Union(_root=True)
class _Optional(_FinalTypingBase, _root=True):
"""Optional type.
Optional[X] is equivalent to Union[X, None].
"""
__slots__ = ()
@_tp_cache
def __getitem__(self, arg):
arg = _type_check(arg, "Optional[t] requires a single type.")
return Union[arg, type(None)]
Optional = _Optional(_root=True)
def _next_in_mro(cls):
"""Helper for Generic.__new__.
Returns the class after the last occurrence of Generic or
Generic[...] in cls.__mro__.
"""
next_in_mro = object
# Look for the last occurrence of Generic or Generic[...].
for i, c in enumerate(cls.__mro__[:-1]):
if isinstance(c, GenericMeta) and c._gorg is Generic:
next_in_mro = cls.__mro__[i + 1]
return next_in_mro
def _make_subclasshook(cls):
"""Construct a __subclasshook__ callable that incorporates
the associated __extra__ class in subclass checks performed
against cls.
"""
if isinstance(cls.__extra__, abc.ABCMeta):
# The logic mirrors that of ABCMeta.__subclasscheck__.
# Registered classes need not be checked here because
# cls and its extra share the same _abc_registry.
def __extrahook__(subclass):
res = cls.__extra__.__subclasshook__(subclass)
if res is not NotImplemented:
return res
if cls.__extra__ in subclass.__mro__:
return True
for scls in cls.__extra__.__subclasses__():
if isinstance(scls, GenericMeta):
continue
if issubclass(subclass, scls):
return True
return NotImplemented
else:
# For non-ABC extras we'll just call issubclass().
def __extrahook__(subclass):
if cls.__extra__ and issubclass(subclass, cls.__extra__):
return True
return NotImplemented
return __extrahook__
def _no_slots_copy(dct):
"""Internal helper: copy class __dict__ and clean slots class variables.
(They will be re-created if necessary by normal class machinery.)
"""
dict_copy = dict(dct)
if '__slots__' in dict_copy:
for slot in dict_copy['__slots__']:
dict_copy.pop(slot, None)
return dict_copy
class GenericMeta(TypingMeta, abc.ABCMeta):
"""Metaclass for generic types.
This is a metaclass for typing.Generic and generic ABCs defined in
typing module. User defined subclasses of GenericMeta can override
__new__ and invoke super().__new__. Note that GenericMeta.__new__
has strict rules on what is allowed in its bases argument:
* plain Generic is disallowed in bases;
* Generic[...] should appear in bases at most once;
* if Generic[...] is present, then it should list all type variables
that appear in other bases.
In addition, type of all generic bases is erased, e.g., C[int] is
stripped to plain C.
"""
def __new__(cls, name, bases, namespace,
tvars=None, args=None, origin=None, extra=None, orig_bases=None):
"""Create a new generic class. GenericMeta.__new__ accepts
keyword arguments that are used for internal bookkeeping, therefore
an override should pass unused keyword arguments to super().
"""
if tvars is not None:
# Called from __getitem__() below.
assert origin is not None
assert all(isinstance(t, TypeVar) for t in tvars), tvars
else:
# Called from class statement.
assert tvars is None, tvars
assert args is None, args
assert origin is None, origin
# Get the full set of tvars from the bases.
tvars = _type_vars(bases)
# Look for Generic[T1, ..., Tn].
# If found, tvars must be a subset of it.
# If not found, tvars is it.
# Also check for and reject plain Generic,
# and reject multiple Generic[...].
gvars = None
for base in bases:
if base is Generic:
raise TypeError("Cannot inherit from plain Generic")
if (isinstance(base, GenericMeta) and
base.__origin__ is Generic):
if gvars is not None:
raise TypeError(
"Cannot inherit from Generic[...] multiple types.")
gvars = base.__parameters__
if gvars is None:
gvars = tvars
else:
tvarset = set(tvars)
gvarset = set(gvars)
if not tvarset <= gvarset:
raise TypeError(
"Some type variables (%s) "
"are not listed in Generic[%s]" %
(", ".join(str(t) for t in tvars if t not in gvarset),
", ".join(str(g) for g in gvars)))
tvars = gvars
initial_bases = bases
if extra is not None and type(extra) is abc.ABCMeta and extra not in bases:
bases = (extra,) + bases
bases = tuple(b._gorg if isinstance(b, GenericMeta) else b for b in bases)
# remove bare Generic from bases if there are other generic bases
if any(isinstance(b, GenericMeta) and b is not Generic for b in bases):
bases = tuple(b for b in bases if b is not Generic)
namespace.update({'__origin__': origin, '__extra__': extra,
'_gorg': None if not origin else origin._gorg})
self = super().__new__(cls, name, bases, namespace, _root=True)
super(GenericMeta, self).__setattr__('_gorg',
self if not origin else origin._gorg)
self.__parameters__ = tvars
# Be prepared that GenericMeta will be subclassed by TupleMeta
# and CallableMeta, those two allow ..., (), or [] in __args___.
self.__args__ = tuple(... if a is _TypingEllipsis else
() if a is _TypingEmpty else
a for a in args) if args else None
# Speed hack (https://github.com/python/typing/issues/196).
self.__next_in_mro__ = _next_in_mro(self)
# Preserve base classes on subclassing (__bases__ are type erased now).
if orig_bases is None:
self.__orig_bases__ = initial_bases
# This allows unparameterized generic collections to be used
# with issubclass() and isinstance() in the same way as their
# collections.abc counterparts (e.g., isinstance([], Iterable)).
if (
'__subclasshook__' not in namespace and extra or
# allow overriding
getattr(self.__subclasshook__, '__name__', '') == '__extrahook__'
):