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__init__.py
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__init__.py
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# encoding: utf-8
#
# Copyright (C) 2010 Alec Thomas <alec@swapoff.org>
# All rights reserved.
#
# This software is licensed as described in the file COPYING, which
# you should have received as part of this distribution.
#
# Author: Alec Thomas <alec@swapoff.org>
"""Injector - Python dependency injection framework, inspired by Guice
:copyright: (c) 2012 by Alec Thomas
:license: BSD
"""
import functools
import inspect
import itertools
import logging
import sys
import threading
import types
from abc import ABCMeta, abstractmethod
from collections import namedtuple
from typing import (
Any,
Callable,
cast,
Dict,
Generic,
Iterable,
List,
Optional,
overload,
Tuple,
Type,
TypeVar,
TYPE_CHECKING,
Union,
)
try:
from typing import NoReturn
except ImportError:
from typing_extensions import NoReturn
HAVE_ANNOTATED = sys.version_info >= (3, 7, 0)
# This is a messy, type-wise, because we not only have two potentially conflicting imports here
# but we also define our own versions in the else block in case we operate on Python 3.6
# which didn't get Annotated support in get_type_hints(). The easiest way to make mypy
# happy here is to tell it the versions from typing_extensions are canonical. Since this
# typing_extensions import is only for mypy it'll work even without typing_extensions actually
# installed so all's good.
if TYPE_CHECKING:
from typing_extensions import _AnnotatedAlias, Annotated, get_type_hints
elif HAVE_ANNOTATED:
# Ignoring errors here as typing_extensions stub doesn't know about those things yet
try:
from typing import _AnnotatedAlias, Annotated, get_type_hints
except ImportError:
from typing_extensions import _AnnotatedAlias, Annotated, get_type_hints
else:
class Annotated:
pass
from typing import get_type_hints as _get_type_hints
def get_type_hints(
obj: Callable[..., Any],
globalns: Optional[Dict[str, Any]] = None,
localns: Optional[Dict[str, Any]] = None,
include_extras: bool = False,
) -> Dict[str, Any]:
return _get_type_hints(obj, globalns, localns)
__author__ = 'Alec Thomas <alec@swapoff.org>'
__version__ = '0.18.4'
__version_tag__ = ''
log = logging.getLogger('injector')
log.addHandler(logging.NullHandler())
if log.level == logging.NOTSET:
log.setLevel(logging.WARN)
T = TypeVar('T')
K = TypeVar('K')
V = TypeVar('V')
def private(something: T) -> T:
something.__private__ = True # type: ignore
return something
CallableT = TypeVar('CallableT', bound=Callable)
def synchronized(lock: threading.RLock) -> Callable[[CallableT], CallableT]:
def outside_wrapper(function: CallableT) -> CallableT:
@functools.wraps(function)
def wrapper(*args: Any, **kwargs: Any) -> Any:
with lock:
return function(*args, **kwargs)
return cast(CallableT, wrapper)
return outside_wrapper
lock = threading.RLock()
_inject_marker = object()
_noinject_marker = object()
if HAVE_ANNOTATED:
InjectT = TypeVar('InjectT')
Inject = Annotated[InjectT, _inject_marker]
"""An experimental way to declare injectable dependencies utilizing a `PEP 593`_ implementation
in Python 3.9 and backported to Python 3.7+ in `typing_extensions`.
Those two declarations are equivalent::
@inject
def fun(t: SomeType) -> None:
pass
def fun(t: Inject[SomeType]) -> None:
pass
The advantage over using :func:`inject` is that if you have some noninjectable parameters
it may be easier to spot what are they. Those two are equivalent::
@inject
@noninjectable('s')
def fun(t: SomeType, s: SomeOtherType) -> None:
pass
def fun(t: Inject[SomeType], s: SomeOtherType) -> None:
pass
.. seealso::
Function :func:`get_bindings`
A way to inspect how various injection declarations interact with each other.
.. versionadded:: 0.18.0
.. note:: Requires Python 3.7+.
.. note::
If you're using mypy you need the version 0.750 or newer to fully type-check code using this
construct.
.. _PEP 593: https://www.python.org/dev/peps/pep-0593/
.. _typing_extensions: https://pypi.org/project/typing-extensions/
"""
NoInject = Annotated[InjectT, _noinject_marker]
"""An experimental way to declare noninjectable dependencies utilizing a `PEP 593`_ implementation
in Python 3.9 and backported to Python 3.7+ in `typing_extensions`.
Since :func:`inject` declares all function's parameters to be injectable there needs to be a way
to opt out of it. This has been provided by :func:`noninjectable` but `noninjectable` suffers from
two issues:
* You need to repeat the parameter name
* The declaration may be relatively distance in space from the actual parameter declaration, thus
hindering readability
`NoInject` solves both of those concerns, for example (those two declarations are equivalent)::
@inject
@noninjectable('b')
def fun(a: TypeA, b: TypeB) -> None:
pass
@inject
def fun(a: TypeA, b: NoInject[TypeB]) -> None:
pass
.. seealso::
Function :func:`get_bindings`
A way to inspect how various injection declarations interact with each other.
.. versionadded:: 0.18.0
.. note:: Requires Python 3.7+.
.. note::
If you're using mypy you need the version 0.750 or newer to fully type-check code using this
construct.
.. _PEP 593: https://www.python.org/dev/peps/pep-0593/
.. _typing_extensions: https://pypi.org/project/typing-extensions/
"""
def reraise(original: Exception, exception: Exception, maximum_frames: int = 1) -> NoReturn:
prev_cls, prev, tb = sys.exc_info()
frames = inspect.getinnerframes(cast(types.TracebackType, tb))
if len(frames) > maximum_frames:
exception = original
raise exception.with_traceback(tb)
class Error(Exception):
"""Base exception."""
class UnsatisfiedRequirement(Error):
"""Requirement could not be satisfied."""
def __init__(self, owner: Optional[object], interface: type) -> None:
super().__init__(owner, interface)
self.owner = owner
self.interface = interface
def __str__(self) -> str:
on = '%s has an ' % _describe(self.owner) if self.owner else ''
return '%sunsatisfied requirement on %s' % (on, _describe(self.interface))
class CallError(Error):
"""Call to callable object fails."""
def __str__(self) -> str:
if len(self.args) == 1:
return self.args[0]
instance, method, args, kwargs, original_error, stack = self.args
cls = instance.__class__.__name__ if instance is not None else ''
full_method = '.'.join((cls, method.__name__)).strip('.')
parameters = ', '.join(
itertools.chain(
(repr(arg) for arg in args), ('%s=%r' % (key, value) for (key, value) in kwargs.items())
)
)
return 'Call to %s(%s) failed: %s (injection stack: %r)' % (
full_method,
parameters,
original_error,
[level[0] for level in stack],
)
class CircularDependency(Error):
"""Circular dependency detected."""
class UnknownProvider(Error):
"""Tried to bind to a type whose provider couldn't be determined."""
class UnknownArgument(Error):
"""Tried to mark an unknown argument as noninjectable."""
class Provider(Generic[T]):
"""Provides class instances."""
__metaclass__ = ABCMeta
@abstractmethod
def get(self, injector: 'Injector') -> T:
raise NotImplementedError # pragma: no cover
class ClassProvider(Provider):
"""Provides instances from a given class, created using an Injector."""
def __init__(self, cls: Type[T]) -> None:
self._cls = cls
def get(self, injector: 'Injector') -> T:
return injector.create_object(self._cls)
class CallableProvider(Provider):
"""Provides something using a callable.
The callable is called every time new value is requested from the provider.
There's no need to explicitly use :func:`inject` or :data:`Inject` with the callable as it's
assumed that, if the callable has annotated parameters, they're meant to be provided
automatically. It wouldn't make sense any other way, as there's no mechanism to provide
parameters to the callable at a later time, so either they'll be injected or there'll be
a `CallError`.
::
>>> class MyClass:
... def __init__(self, value: int) -> None:
... self.value = value
...
>>> def factory():
... print('providing')
... return MyClass(42)
...
>>> def configure(binder):
... binder.bind(MyClass, to=CallableProvider(factory))
...
>>> injector = Injector(configure)
>>> injector.get(MyClass) is injector.get(MyClass)
providing
providing
False
"""
def __init__(self, callable: Callable[..., T]):
self._callable = callable
def get(self, injector: 'Injector') -> T:
return injector.call_with_injection(self._callable)
def __repr__(self) -> str:
return '%s(%r)' % (type(self).__name__, self._callable)
class InstanceProvider(Provider):
"""Provide a specific instance.
::
>>> class MyType:
... def __init__(self):
... self.contents = []
>>> def configure(binder):
... binder.bind(MyType, to=InstanceProvider(MyType()))
...
>>> injector = Injector(configure)
>>> injector.get(MyType) is injector.get(MyType)
True
>>> injector.get(MyType).contents.append('x')
>>> injector.get(MyType).contents
['x']
"""
def __init__(self, instance: T) -> None:
self._instance = instance
def get(self, injector: 'Injector') -> T:
return self._instance
def __repr__(self) -> str:
return '%s(%r)' % (type(self).__name__, self._instance)
@private
class ListOfProviders(Provider, Generic[T]):
"""Provide a list of instances via other Providers."""
_providers: List[Provider[T]]
def __init__(self) -> None:
self._providers = []
def append(self, provider: Provider[T]) -> None:
self._providers.append(provider)
def __repr__(self) -> str:
return '%s(%r)' % (type(self).__name__, self._providers)
class MultiBindProvider(ListOfProviders[List[T]]):
"""Used by :meth:`Binder.multibind` to flatten results of providers that
return sequences."""
def get(self, injector: 'Injector') -> List[T]:
return [i for provider in self._providers for i in provider.get(injector)]
class MapBindProvider(ListOfProviders[Dict[str, T]]):
"""A provider for map bindings."""
def get(self, injector: 'Injector') -> Dict[str, T]:
map: Dict[str, T] = {}
for provider in self._providers:
map.update(provider.get(injector))
return map
_BindingBase = namedtuple('_BindingBase', 'interface provider scope')
@private
class Binding(_BindingBase):
"""A binding from an (interface,) to a provider in a scope."""
def is_multibinding(self) -> bool:
return _get_origin(_punch_through_alias(self.interface)) in {dict, list}
_InstallableModuleType = Union[Callable[['Binder'], None], 'Module', Type['Module']]
class Binder:
"""Bind interfaces to implementations.
.. note:: This class is instantiated internally for you and there's no need
to instantiate it on your own.
"""
_bindings: Dict[type, Binding]
@private
def __init__(self, injector: 'Injector', auto_bind: bool = True, parent: 'Binder' = None) -> None:
"""Create a new Binder.
:param injector: Injector we are binding for.
:param auto_bind: Whether to automatically bind missing types.
:param parent: Parent binder.
"""
self.injector = injector
self._auto_bind = auto_bind
self._bindings = {}
self.parent = parent
def bind(
self,
interface: Type[T],
to: Union[None, T, Callable[..., T], Provider[T]] = None,
scope: Union[None, Type['Scope'], 'ScopeDecorator'] = None,
) -> None:
"""Bind an interface to an implementation.
Binding `T` to an instance of `T` like
::
binder.bind(A, to=A('some', 'thing'))
is, for convenience, a shortcut for
::
binder.bind(A, to=InstanceProvider(A('some', 'thing'))).
Likewise, binding to a callable like
::
binder.bind(A, to=some_callable)
is a shortcut for
::
binder.bind(A, to=CallableProvider(some_callable))
and, as such, if `some_callable` there has any annotated parameters they'll be provided
automatically without having to use :func:`inject` or :data:`Inject` with the callable.
`typing.List` and `typing.Dict` instances are reserved for multibindings and trying to bind them
here will result in an error (use :meth:`multibind` instead)::
binder.bind(List[str], to=['hello', 'there']) # Error
:param interface: Type to bind.
:param to: Instance or class to bind to, or an instance of
:class:`Provider` subclass.
:param scope: Optional :class:`Scope` in which to bind.
"""
if _get_origin(_punch_through_alias(interface)) in {dict, list}:
raise Error(
'Type %s is reserved for multibindings. Use multibind instead of bind.' % (interface,)
)
self._bindings[interface] = self.create_binding(interface, to, scope)
@overload
def multibind(
self,
interface: Type[List[T]],
to: Union[List[T], Callable[..., List[T]], Provider[List[T]]],
scope: Union[Type['Scope'], 'ScopeDecorator'] = None,
) -> None: # pragma: no cover
pass
@overload
def multibind(
self,
interface: Type[Dict[K, V]],
to: Union[Dict[K, V], Callable[..., Dict[K, V]], Provider[Dict[K, V]]],
scope: Union[Type['Scope'], 'ScopeDecorator'] = None,
) -> None: # pragma: no cover
pass
def multibind(
self, interface: type, to: Any, scope: Union['ScopeDecorator', Type['Scope']] = None
) -> None:
"""Creates or extends a multi-binding.
A multi-binding contributes values to a list or to a dictionary. For example::
binder.multibind(List[str], to=['some', 'strings'])
binder.multibind(List[str], to=['other', 'strings'])
injector.get(List[str]) # ['some', 'strings', 'other', 'strings']
binder.multibind(Dict[str, int], to={'key': 11})
binder.multibind(Dict[str, int], to={'other_key': 33})
injector.get(Dict[str, int]) # {'key': 11, 'other_key': 33}
.. versionchanged:: 0.17.0
Added support for using `typing.Dict` and `typing.List` instances as interfaces.
Deprecated support for `MappingKey`, `SequenceKey` and single-item lists and
dictionaries as interfaces.
:param interface: typing.Dict or typing.List instance to bind to.
:param to: Instance, class to bind to, or an explicit :class:`Provider`
subclass. Must provide a list or a dictionary, depending on the interface.
:param scope: Optional Scope in which to bind.
"""
if interface not in self._bindings:
provider: ListOfProviders
if (
isinstance(interface, dict)
or isinstance(interface, type)
and issubclass(interface, dict)
or _get_origin(_punch_through_alias(interface)) is dict
):
provider = MapBindProvider()
else:
provider = MultiBindProvider()
binding = self.create_binding(interface, provider, scope)
self._bindings[interface] = binding
else:
binding = self._bindings[interface]
provider = binding.provider
assert isinstance(provider, ListOfProviders)
provider.append(self.provider_for(interface, to))
def install(self, module: _InstallableModuleType) -> None:
"""Install a module into this binder.
In this context the module is one of the following:
* function taking the :class:`Binder` as it's only parameter
::
def configure(binder):
bind(str, to='s')
binder.install(configure)
* instance of :class:`Module` (instance of it's subclass counts)
::
class MyModule(Module):
def configure(self, binder):
binder.bind(str, to='s')
binder.install(MyModule())
* subclass of :class:`Module` - the subclass needs to be instantiable so if it
expects any parameters they need to be injected
::
binder.install(MyModule)
"""
if type(module) is type and issubclass(cast(type, module), Module):
instance = cast(type, module)()
else:
instance = module
instance(self)
def create_binding(
self, interface: type, to: Any = None, scope: Union['ScopeDecorator', Type['Scope']] = None
) -> Binding:
provider = self.provider_for(interface, to)
scope = scope or getattr(to or interface, '__scope__', NoScope)
if isinstance(scope, ScopeDecorator):
scope = scope.scope
return Binding(interface, provider, scope)
def provider_for(self, interface: Any, to: Any = None) -> Provider:
base_type = _punch_through_alias(interface)
origin = _get_origin(base_type)
if interface is Any:
raise TypeError('Injecting Any is not supported')
elif _is_specialization(interface, ProviderOf):
(target,) = interface.__args__
if to is not None:
raise Exception('ProviderOf cannot be bound to anything')
return InstanceProvider(ProviderOf(self.injector, target))
elif isinstance(to, Provider):
return to
elif isinstance(
to,
(
types.FunctionType,
types.LambdaType,
types.MethodType,
types.BuiltinFunctionType,
types.BuiltinMethodType,
),
):
return CallableProvider(to)
elif issubclass(type(to), type):
return ClassProvider(cast(type, to))
elif isinstance(interface, BoundKey):
def proxy(injector: Injector) -> Any:
binder = injector.binder
kwarg_providers = {
name: binder.provider_for(None, provider) for (name, provider) in interface.kwargs.items()
}
kwargs = {name: provider.get(injector) for (name, provider) in kwarg_providers.items()}
return interface.interface(**kwargs)
return CallableProvider(inject(proxy))
elif _is_specialization(interface, AssistedBuilder):
(target,) = interface.__args__
builder = interface(self.injector, target)
return InstanceProvider(builder)
elif (
origin is None
and isinstance(base_type, (tuple, type))
and interface is not Any
and isinstance(to, base_type)
or origin in {dict, list}
and isinstance(to, origin)
):
return InstanceProvider(to)
elif issubclass(type(base_type), type) or isinstance(base_type, (tuple, list)):
if to is not None:
return InstanceProvider(to)
return ClassProvider(base_type)
else:
raise UnknownProvider('couldn\'t determine provider for %r to %r' % (interface, to))
def _get_binding(self, key: type, *, only_this_binder: bool = False) -> Tuple[Binding, 'Binder']:
binding = self._bindings.get(key)
if binding:
return binding, self
if self.parent and not only_this_binder:
return self.parent._get_binding(key)
raise KeyError
def get_binding(self, interface: type) -> Tuple[Binding, 'Binder']:
is_scope = isinstance(interface, type) and issubclass(interface, Scope)
try:
return self._get_binding(interface, only_this_binder=is_scope)
except (KeyError, UnsatisfiedRequirement):
if is_scope:
scope = interface
self.bind(scope, to=scope(self.injector))
return self._get_binding(interface)
# The special interface is added here so that requesting a special
# interface with auto_bind disabled works
if self._auto_bind or self._is_special_interface(interface):
binding = self.create_binding(interface)
self._bindings[interface] = binding
return binding, self
raise UnsatisfiedRequirement(None, interface)
def _is_special_interface(self, interface: type) -> bool:
# "Special" interfaces are ones that you cannot bind yourself but
# you can request them (for example you cannot bind ProviderOf(SomeClass)
# to anything but you can inject ProviderOf(SomeClass) just fine
return any(_is_specialization(interface, cls) for cls in [AssistedBuilder, ProviderOf])
def _is_specialization(cls: type, generic_class: Any) -> bool:
# Starting with typing 3.5.3/Python 3.6 it is no longer necessarily true that
# issubclass(SomeGeneric[X], SomeGeneric) so we need some other way to
# determine whether a particular object is a generic class with type parameters
# provided. Fortunately there seems to be __origin__ attribute that's useful here.
# We need to special-case Annotated as its __origin__ behaves differently than
# other typing generic classes. See https://github.com/python/typing/pull/635
# for some details.
if HAVE_ANNOTATED and generic_class is Annotated and isinstance(cls, _AnnotatedAlias):
return True
if not hasattr(cls, '__origin__'):
return False
origin = cast(Any, cls).__origin__
if not inspect.isclass(generic_class):
generic_class = type(generic_class)
if not inspect.isclass(origin):
origin = type(origin)
# __origin__ is generic_class is a special case to handle Union as
# Union cannot be used in issubclass() check (it raises an exception
# by design).
return origin is generic_class or issubclass(origin, generic_class)
def _punch_through_alias(type_: Any) -> type:
if getattr(type_, '__qualname__', '') == 'NewType.<locals>.new_type':
return type_.__supertype__
else:
return type_
def _get_origin(type_: type) -> type:
origin = getattr(type_, '__origin__', None)
# Older typing behaves differently there and stores Dict and List as origin, we need to be flexible.
if origin is List:
return list
elif origin is Dict:
return dict
return origin
class Scope:
"""A Scope looks up the Provider for a binding.
By default (ie. :class:`NoScope` ) this simply returns the default
:class:`Provider` .
"""
__metaclass__ = ABCMeta
def __init__(self, injector: 'Injector') -> None:
self.injector = injector
self.configure()
def configure(self) -> None:
"""Configure the scope."""
@abstractmethod
def get(self, key: Type[T], provider: Provider[T]) -> Provider[T]:
"""Get a :class:`Provider` for a key.
:param key: The key to return a provider for.
:param provider: The default Provider associated with the key.
:returns: A Provider instance that can provide an instance of key.
"""
raise NotImplementedError # pragma: no cover
class ScopeDecorator:
def __init__(self, scope: Type[Scope]) -> None:
self.scope = scope
def __call__(self, cls: T) -> T:
cast(Any, cls).__scope__ = self.scope
binding = getattr(cls, '__binding__', None)
if binding:
new_binding = Binding(interface=binding.interface, provider=binding.provider, scope=self.scope)
setattr(cls, '__binding__', new_binding)
return cls
def __repr__(self) -> str:
return 'ScopeDecorator(%s)' % self.scope.__name__
class NoScope(Scope):
"""An unscoped provider."""
def get(self, unused_key: Type[T], provider: Provider[T]) -> Provider[T]:
return provider
noscope = ScopeDecorator(NoScope)
class SingletonScope(Scope):
"""A :class:`Scope` that returns a per-Injector instance for a key.
:data:`singleton` can be used as a convenience class decorator.
>>> class A: pass
>>> injector = Injector()
>>> provider = ClassProvider(A)
>>> singleton = SingletonScope(injector)
>>> a = singleton.get(A, provider)
>>> b = singleton.get(A, provider)
>>> a is b
True
"""
_context: Dict[type, Provider]
def configure(self) -> None:
self._context = {}
@synchronized(lock)
def get(self, key: Type[T], provider: Provider[T]) -> Provider[T]:
try:
return self._context[key]
except KeyError:
provider = InstanceProvider(provider.get(self.injector))
self._context[key] = provider
return provider
singleton = ScopeDecorator(SingletonScope)
class ThreadLocalScope(Scope):
"""A :class:`Scope` that returns a per-thread instance for a key."""
def configure(self) -> None:
self._locals = threading.local()
def get(self, key: Type[T], provider: Provider[T]) -> Provider[T]:
try:
return getattr(self._locals, repr(key))
except AttributeError:
provider = InstanceProvider(provider.get(self.injector))
setattr(self._locals, repr(key), provider)
return provider
threadlocal = ScopeDecorator(ThreadLocalScope)
class Module:
"""Configures injector and providers."""
def __call__(self, binder: Binder) -> None:
"""Configure the binder."""
self.__injector__ = binder.injector
for unused_name, function in inspect.getmembers(self, inspect.ismethod):
binding = None
if hasattr(function, '__binding__'):
binding = function.__binding__
if binding.interface == '__deferred__':
# We could not evaluate a forward reference at @provider-decoration time, we need to
# try again now.
try:
annotations = get_type_hints(function)
except NameError as e:
raise NameError(
'Cannot avaluate forward reference annotation(s) in method %r belonging to %r: %s'
% (function.__name__, type(self), e)
) from e
return_type = annotations['return']
binding = function.__func__.__binding__ = Binding(
interface=return_type, provider=binding.provider, scope=binding.scope
)
bind_method = binder.multibind if binding.is_multibinding() else binder.bind
bind_method( # type: ignore
binding.interface, to=types.MethodType(binding.provider, self), scope=binding.scope
)
self.configure(binder)
def configure(self, binder: Binder) -> None:
"""Override to configure bindings."""
class Injector:
"""
:param modules: Optional - a configuration module or iterable of configuration modules.
Each module will be installed in current :class:`Binder` using :meth:`Binder.install`.
Consult :meth:`Binder.install` documentation for the details.
:param auto_bind: Whether to automatically bind missing types.
:param parent: Parent injector.
.. versionadded:: 0.7.5
``use_annotations`` parameter
.. versionchanged:: 0.13.0
``use_annotations`` parameter is removed
"""
_stack: Tuple[Tuple[object, Callable, Tuple[Tuple[str, type], ...]], ...]
binder: Binder
def __init__(
self,
modules: Union[_InstallableModuleType, Iterable[_InstallableModuleType]] = None,
auto_bind: bool = True,
parent: 'Injector' = None,
) -> None:
# Stack of keys currently being injected. Used to detect circular
# dependencies.
self._stack = ()
self.parent = parent
# Binder
self.binder = Binder(self, auto_bind=auto_bind, parent=parent.binder if parent is not None else None)
if not modules:
modules = []
elif not hasattr(modules, '__iter__'):
modules = [cast(_InstallableModuleType, modules)]
# This line is needed to pelase mypy. We know we have Iteable of modules here.
modules = cast(Iterable[_InstallableModuleType], modules)
# Bind some useful types
self.binder.bind(Injector, to=self)
self.binder.bind(Binder, to=self.binder)
# Initialise modules
for module in modules:
self.binder.install(module)
@property
def _log_prefix(self) -> str:
return '>' * (len(self._stack) + 1) + ' '
def get(self, interface: Type[T], scope: Union[ScopeDecorator, Type[Scope]] = None) -> T:
"""Get an instance of the given interface.
.. note::
Although this method is part of :class:`Injector`'s public interface
it's meant to be used in limited set of circumstances.
For example, to create some kind of root object (application object)
of your application (note that only one `get` call is needed,
inside the `Application` class and any of its dependencies
:func:`inject` can and should be used):
.. code-block:: python
class Application:
@inject
def __init__(self, dep1: Dep1, dep2: Dep2):
self.dep1 = dep1
self.dep2 = dep2
def run(self):
self.dep1.something()
injector = Injector(configuration)
application = injector.get(Application)
application.run()
:param interface: Interface whose implementation we want.
:param scope: Class of the Scope in which to resolve.
:returns: An implementation of interface.
"""
binding, binder = self.binder.get_binding(interface)
scope = scope or binding.scope
if isinstance(scope, ScopeDecorator):
scope = scope.scope
# Fetch the corresponding Scope instance from the Binder.
scope_binding, _ = binder.get_binding(scope)
scope_instance = scope_binding.provider.get(self)
log.debug(
'%sInjector.get(%r, scope=%r) using %r', self._log_prefix, interface, scope, binding.provider
)
result = scope_instance.get(interface, binding.provider).get(self)
log.debug('%s -> %r', self._log_prefix, result)
return result
def create_child_injector(self, *args: Any, **kwargs: Any) -> 'Injector':
kwargs['parent'] = self
return Injector(*args, **kwargs)
def create_object(self, cls: Type[T], additional_kwargs: Any = None) -> T:
"""Create a new instance, satisfying any dependencies on cls."""
additional_kwargs = additional_kwargs or {}
log.debug('%sCreating %r object with %r', self._log_prefix, cls, additional_kwargs)
try:
instance = cls.__new__(cls)
except TypeError as e:
reraise(
e,
CallError(cls, getattr(cls.__new__, '__func__', cls.__new__), (), {}, e, self._stack),
maximum_frames=2,
)
init = cls.__init__
try:
self.call_with_injection(init, self_=instance, kwargs=additional_kwargs)
except TypeError as e:
reraise(e, CallError(instance, instance.__init__.__func__, (), additional_kwargs, e, self._stack))
return instance
def call_with_injection(
self, callable: Callable[..., T], self_: Any = None, args: Any = (), kwargs: Any = {}
) -> T:
"""Call a callable and provide it's dependencies if needed.
:param self_: Instance of a class callable belongs to if it's a method,
None otherwise.
:param args: Arguments to pass to callable.
:param kwargs: Keyword arguments to pass to callable.
:type callable: callable
:type args: tuple of objects
:type kwargs: dict of string -> object
:return: Value returned by callable.
"""
bindings = get_bindings(callable)
signature = inspect.signature(callable)
full_args = args
if self_ is not None: