150 lines
4.4 KiB
Python
150 lines
4.4 KiB
Python
"""Injections module."""
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import sys
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import itertools
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import six
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from .utils import is_provider
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from .utils import is_injection
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from .utils import is_arg_injection
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from .utils import is_kwarg_injection
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from .errors import Error
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IS_PYPY = '__pypy__' in sys.builtin_module_names
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if IS_PYPY or six.PY3: # pragma: no cover
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OBJECT_INIT = six.get_unbound_function(object.__init__)
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else: # pragma: no cover
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OBJECT_INIT = None
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class Injection(object):
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"""Base injection class."""
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__IS_INJECTION__ = True
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__slots__ = ('injectable', 'is_provider')
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def __init__(self, injectable):
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"""Initializer."""
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self.injectable = injectable
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self.is_provider = is_provider(injectable)
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@property
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def value(self):
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"""Return injectable value."""
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if self.is_provider:
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return self.injectable()
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return self.injectable
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class _NamedInjection(Injection):
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"""Base class of named injections."""
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__slots__ = ('name',)
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def __init__(self, name, injectable):
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"""Initializer."""
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self.name = name
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super(_NamedInjection, self).__init__(injectable)
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class Arg(Injection):
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"""Positional argument injection."""
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__IS_ARG_INJECTION__ = True
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class KwArg(_NamedInjection):
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"""Keyword argument injection."""
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__IS_KWARG_INJECTION__ = True
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class Attribute(_NamedInjection):
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"""Attribute injection."""
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__IS_ATTRIBUTE_INJECTION__ = True
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class Method(_NamedInjection):
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"""Method injection."""
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__IS_METHOD_INJECTION__ = True
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def inject(*args, **kwargs):
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"""Dependency injection decorator.
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:return: (callable) -> (callable)
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"""
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arg_injections = _parse_args_injections(args)
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kwarg_injections = _parse_kwargs_injections(args, kwargs)
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def decorator(callback_or_cls):
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"""Dependency injection decorator."""
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if isinstance(callback_or_cls, six.class_types):
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cls = callback_or_cls
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try:
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cls_init = six.get_unbound_function(cls.__init__)
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assert cls_init is not OBJECT_INIT
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except (AttributeError, AssertionError):
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raise Error(
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'Class {0}.{1} has no __init__() '.format(cls.__module__,
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cls.__name__) +
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'method and could not be decorated with @inject decorator')
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cls.__init__ = decorator(cls_init)
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return cls
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callback = callback_or_cls
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if hasattr(callback, 'injections'):
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callback.args += arg_injections
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callback.kwargs += kwarg_injections
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callback.injections += arg_injections + kwarg_injections
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return callback
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@six.wraps(callback)
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def decorated(*args, **kwargs):
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"""Decorated with dependency injection callback."""
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return callback(*_get_injectable_args(args, decorated.args),
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**_get_injectable_kwargs(kwargs, decorated.kwargs))
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decorated.args = arg_injections
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decorated.kwargs = kwarg_injections
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decorated.injections = arg_injections + kwarg_injections
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return decorated
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return decorator
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def _parse_args_injections(args):
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"""Parse positional argument injections according to current syntax."""
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return tuple(Arg(arg) if not is_injection(arg) else arg
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for arg in args
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if not is_injection(arg) or is_arg_injection(arg))
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def _parse_kwargs_injections(args, kwargs):
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"""Parse keyword argument injections according to current syntax."""
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kwarg_injections = tuple(injection
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for injection in args
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if is_kwarg_injection(injection))
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if kwargs:
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kwarg_injections += tuple(KwArg(name, value)
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for name, value in six.iteritems(kwargs))
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return kwarg_injections
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def _get_injectable_args(context_args, arg_injections):
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"""Return tuple of positional arguments, patched with injections."""
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return itertools.chain((arg.value for arg in arg_injections), context_args)
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def _get_injectable_kwargs(context_kwargs, kwarg_injections):
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"""Return dictionary of keyword arguments, patched with injections."""
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injectable_kwargs = dict((kwarg.name, kwarg.value)
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for kwarg in kwarg_injections)
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injectable_kwargs.update(context_kwargs)
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return injectable_kwargs
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