# --------------------------------------------------------------------------------------
# Copyright (c) 2013-2021, Nucleic Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file LICENSE, distributed with this software.
# --------------------------------------------------------------------------------------
from .catom import DefaultValue, Member, Validate
from .typing_utils import extract_types, is_optional
class Typed(Member):
"""A value which allows objects of a given type or types.
Values will be tested using the `PyObject_TypeCheck` C API call.
This call is equivalent to `type(obj) in cls.mro()`. It is less
flexible but can be faster than Instance. Use Instance when allowing
you need a tuple of types or (abstract) types relying on custom
__isinstancecheck__ and Typed when the value type is explicit.
If optional is True, the value of a Typed may be set to None,
otherwise None is not considered as a valid value.
"""
__slots__ = ()
def __init__(self, kind, args=None, kwargs=None, *, factory=None, optional=None):
"""Initialize an Typed.
Parameters
----------
kind : type
The allowed type for the value.
args : tuple, optional
If 'factory' is None, then 'kind' is a callable type and
these arguments will be passed to the constructor to create
the default value.
kwargs : dict, optional
If 'factory' is None, then 'kind' is a callable type and
these keywords will be passed to the constructor to create
the default value.
factory : callable, optional
An optional factory to use for creating the default value.
If this is not provided and 'args' and 'kwargs' is None,
then the default value will be None, which will raised if
accessed when optional is False.
optional : bool | None, optional
Boolean indicating if None is a valid value for the member.
By default, the value is inferred to be True if no args or factory
is provided.
"""
opt, (kind,) = is_optional(extract_types(kind))
if opt and optional is False:
raise ValueError(
"The type passed to Typed is declared optional but optional was "
"explicitly set to False"
)
# If opt is False we preserve optional as None for backward compatibility.
optional = optional if optional is not None else (opt or None)
if factory is not None:
self.set_default_value_mode(DefaultValue.CallObject, factory)
elif args is not None or kwargs is not None:
args = args or ()
kwargs = kwargs or {}
factory = lambda: kind(*args, **kwargs)
self.set_default_value_mode(DefaultValue.CallObject, factory)
elif optional is False:
self.set_default_value_mode(DefaultValue.NonOptional, None)
optional = (
optional
if optional is not None
else factory is None and args is None and kwargs is None
)
if optional:
self.set_validate_mode(Validate.OptionalTyped, kind)
else:
self.set_validate_mode(Validate.Typed, kind)
class ForwardTyped(Typed):
"""A Typed which delays resolving the type definition.
The first time the value is accessed or modified, the type will
be resolved and the forward typed will behave identically to a
normal typed.
"""
__slots__ = ("resolve", "args", "kwargs", "optional")
def __init__(self, resolve, args=None, kwargs=None, *, factory=None, optional=None):
"""Initialize a ForwardTyped.
resolve : callable
A callable which takes no arguments and returns the type to
use for validating the values. This type can be a generic but
must resolve to a single type. list[int] is valid but Optional[int]
is not.
args : tuple, optional
If 'factory' is None, then 'resolve' will return a callable
type and these arguments will be passed to the constructor
to create the default value.
kwargs : dict, optional
If 'factory' is None, then 'resolve' will return a callable
type and these keywords will be passed to the constructor to
create the default value.
factory : callable, optional
An optional factory to use for creating the default value.
If this is not provided and 'args' and 'kwargs' is None,
then the default value will be None, which will raised if
accessed when optional is False.
optional : bool | None, optional
Boolean indicating if None is a valid value for the member.
By default, the value is inferred to be True if no args or factory
is provided.
"""
self.resolve = resolve
self.args = args
self.kwargs = kwargs
if factory is not None:
self.set_default_value_mode(DefaultValue.CallObject, factory)
elif args is not None or kwargs is not None:
mode = DefaultValue.MemberMethod_Object
self.set_default_value_mode(mode, "default")
elif optional is False:
self.set_default_value_mode(DefaultValue.NonOptional, None)
self.optional = (
optional
if optional is not None
else factory is None and args is None and kwargs is None
)
self.set_validate_mode(Validate.MemberMethod_ObjectOldNew, "validate")
def default(self, owner):
"""Called to retrieve the default value.
This is called the first time the default value is retrieved
for the member. It resolves the type and updates the internal
default handler to behave like a normal Typed member.
"""
(kind,) = extract_types(self.resolve())
args = self.args or ()
kwargs = self.kwargs or {}
factory = lambda: kind(*args, **kwargs)
self.set_default_value_mode(DefaultValue.CallObject, factory)
return kind(*args, **kwargs)
def validate(self, owner, old, new):
"""Called to validate the value.
This is called the first time a value is validated for the
member. It resolves the type and updates the internal validate
handler to behave like a normal Typed member.
"""
(kind,) = extract_types(self.resolve())
if self.optional:
self.set_validate_mode(Validate.OptionalTyped, kind)
else:
self.set_validate_mode(Validate.Typed, kind)
return self.do_validate(owner, old, new)
def clone(self):
"""Create a clone of the ForwardTyped instance."""
clone = super(ForwardTyped, self).clone()
clone.resolve = self.resolve
clone.args = self.args
clone.kwargs = self.kwargs
clone.optional = self.optional
return clone
