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2a17bde930
Along the way, dismantle importlib._bootstrap._SpecMethods as it was no longer relevant and constructing the new function required partially dismantling the class anyway.
296 lines
11 KiB
Python
296 lines
11 KiB
Python
"""Utility code for constructing importers, etc."""
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from . import abc
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from ._bootstrap import MAGIC_NUMBER
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from ._bootstrap import cache_from_source
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from ._bootstrap import decode_source
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from ._bootstrap import module_from_spec
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from ._bootstrap import source_from_cache
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from ._bootstrap import spec_from_loader
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from ._bootstrap import spec_from_file_location
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from ._bootstrap import _resolve_name
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from ._bootstrap import _find_spec
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from contextlib import contextmanager
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import functools
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import sys
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import types
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import warnings
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def resolve_name(name, package):
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"""Resolve a relative module name to an absolute one."""
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if not name.startswith('.'):
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return name
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elif not package:
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raise ValueError('{!r} is not a relative name '
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'(no leading dot)'.format(name))
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level = 0
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for character in name:
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if character != '.':
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break
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level += 1
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return _resolve_name(name[level:], package, level)
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def _find_spec_from_path(name, path=None):
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"""Return the spec for the specified module.
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First, sys.modules is checked to see if the module was already imported. If
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so, then sys.modules[name].__spec__ is returned. If that happens to be
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set to None, then ValueError is raised. If the module is not in
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sys.modules, then sys.meta_path is searched for a suitable spec with the
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value of 'path' given to the finders. None is returned if no spec could
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be found.
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Dotted names do not have their parent packages implicitly imported. You will
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most likely need to explicitly import all parent packages in the proper
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order for a submodule to get the correct spec.
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"""
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if name not in sys.modules:
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return _find_spec(name, path)
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else:
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module = sys.modules[name]
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if module is None:
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return None
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try:
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spec = module.__spec__
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except AttributeError:
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raise ValueError('{}.__spec__ is not set'.format(name))
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else:
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if spec is None:
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raise ValueError('{}.__spec__ is None'.format(name))
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return spec
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def find_spec(name, package=None):
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"""Return the spec for the specified module.
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First, sys.modules is checked to see if the module was already imported. If
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so, then sys.modules[name].__spec__ is returned. If that happens to be
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set to None, then ValueError is raised. If the module is not in
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sys.modules, then sys.meta_path is searched for a suitable spec with the
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value of 'path' given to the finders. None is returned if no spec could
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be found.
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If the name is for submodule (contains a dot), the parent module is
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automatically imported.
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The name and package arguments work the same as importlib.import_module().
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In other words, relative module names (with leading dots) work.
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"""
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fullname = resolve_name(name, package) if name.startswith('.') else name
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if fullname not in sys.modules:
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parent_name = fullname.rpartition('.')[0]
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if parent_name:
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# Use builtins.__import__() in case someone replaced it.
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parent = __import__(parent_name, fromlist=['__path__'])
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return _find_spec(fullname, parent.__path__)
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else:
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return _find_spec(fullname, None)
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else:
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module = sys.modules[fullname]
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if module is None:
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return None
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try:
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spec = module.__spec__
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except AttributeError:
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raise ValueError('{}.__spec__ is not set'.format(name))
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else:
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if spec is None:
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raise ValueError('{}.__spec__ is None'.format(name))
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return spec
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@contextmanager
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def _module_to_load(name):
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is_reload = name in sys.modules
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module = sys.modules.get(name)
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if not is_reload:
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# This must be done before open() is called as the 'io' module
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# implicitly imports 'locale' and would otherwise trigger an
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# infinite loop.
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module = type(sys)(name)
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# This must be done before putting the module in sys.modules
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# (otherwise an optimization shortcut in import.c becomes wrong)
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module.__initializing__ = True
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sys.modules[name] = module
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try:
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yield module
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except Exception:
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if not is_reload:
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try:
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del sys.modules[name]
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except KeyError:
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pass
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finally:
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module.__initializing__ = False
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def set_package(fxn):
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"""Set __package__ on the returned module.
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This function is deprecated.
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"""
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@functools.wraps(fxn)
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def set_package_wrapper(*args, **kwargs):
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warnings.warn('The import system now takes care of this automatically.',
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DeprecationWarning, stacklevel=2)
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module = fxn(*args, **kwargs)
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if getattr(module, '__package__', None) is None:
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module.__package__ = module.__name__
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if not hasattr(module, '__path__'):
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module.__package__ = module.__package__.rpartition('.')[0]
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return module
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return set_package_wrapper
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def set_loader(fxn):
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"""Set __loader__ on the returned module.
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This function is deprecated.
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"""
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@functools.wraps(fxn)
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def set_loader_wrapper(self, *args, **kwargs):
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warnings.warn('The import system now takes care of this automatically.',
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DeprecationWarning, stacklevel=2)
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module = fxn(self, *args, **kwargs)
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if getattr(module, '__loader__', None) is None:
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module.__loader__ = self
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return module
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return set_loader_wrapper
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def module_for_loader(fxn):
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"""Decorator to handle selecting the proper module for loaders.
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The decorated function is passed the module to use instead of the module
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name. The module passed in to the function is either from sys.modules if
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it already exists or is a new module. If the module is new, then __name__
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is set the first argument to the method, __loader__ is set to self, and
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__package__ is set accordingly (if self.is_package() is defined) will be set
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before it is passed to the decorated function (if self.is_package() does
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not work for the module it will be set post-load).
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If an exception is raised and the decorator created the module it is
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subsequently removed from sys.modules.
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The decorator assumes that the decorated function takes the module name as
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the second argument.
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"""
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warnings.warn('The import system now takes care of this automatically.',
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DeprecationWarning, stacklevel=2)
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@functools.wraps(fxn)
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def module_for_loader_wrapper(self, fullname, *args, **kwargs):
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with _module_to_load(fullname) as module:
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module.__loader__ = self
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try:
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is_package = self.is_package(fullname)
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except (ImportError, AttributeError):
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pass
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else:
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if is_package:
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module.__package__ = fullname
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else:
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module.__package__ = fullname.rpartition('.')[0]
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# If __package__ was not set above, __import__() will do it later.
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return fxn(self, module, *args, **kwargs)
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return module_for_loader_wrapper
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class _Module(types.ModuleType):
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"""A subclass of the module type to allow __class__ manipulation."""
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class _LazyModule(types.ModuleType):
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"""A subclass of the module type which triggers loading upon attribute access."""
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def __getattribute__(self, attr):
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"""Trigger the load of the module and return the attribute."""
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# All module metadata must be garnered from __spec__ in order to avoid
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# using mutated values.
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# Stop triggering this method.
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self.__class__ = _Module
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# Get the original name to make sure no object substitution occurred
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# in sys.modules.
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original_name = self.__spec__.name
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# Figure out exactly what attributes were mutated between the creation
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# of the module and now.
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attrs_then = self.__spec__.loader_state
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attrs_now = self.__dict__
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attrs_updated = {}
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for key, value in attrs_now.items():
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# Code that set the attribute may have kept a reference to the
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# assigned object, making identity more important than equality.
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if key not in attrs_then:
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attrs_updated[key] = value
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elif id(attrs_now[key]) != id(attrs_then[key]):
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attrs_updated[key] = value
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self.__spec__.loader.exec_module(self)
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# If exec_module() was used directly there is no guarantee the module
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# object was put into sys.modules.
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if original_name in sys.modules:
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if id(self) != id(sys.modules[original_name]):
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msg = ('module object for {!r} substituted in sys.modules '
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'during a lazy load')
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raise ValueError(msg.format(original_name))
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# Update after loading since that's what would happen in an eager
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# loading situation.
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self.__dict__.update(attrs_updated)
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return getattr(self, attr)
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def __delattr__(self, attr):
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"""Trigger the load and then perform the deletion."""
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# To trigger the load and raise an exception if the attribute
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# doesn't exist.
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self.__getattribute__(attr)
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delattr(self, attr)
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class LazyLoader(abc.Loader):
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"""A loader that creates a module which defers loading until attribute access."""
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@staticmethod
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def __check_eager_loader(loader):
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if not hasattr(loader, 'exec_module'):
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raise TypeError('loader must define exec_module()')
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elif hasattr(loader.__class__, 'create_module'):
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if abc.Loader.create_module != loader.__class__.create_module:
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# Only care if create_module() is overridden in a subclass of
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# importlib.abc.Loader.
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raise TypeError('loader cannot define create_module()')
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@classmethod
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def factory(cls, loader):
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"""Construct a callable which returns the eager loader made lazy."""
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cls.__check_eager_loader(loader)
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return lambda *args, **kwargs: cls(loader(*args, **kwargs))
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def __init__(self, loader):
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self.__check_eager_loader(loader)
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self.loader = loader
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def create_module(self, spec):
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"""Create a module which can have its __class__ manipulated."""
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return _Module(spec.name)
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def exec_module(self, module):
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"""Make the module load lazily."""
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module.__spec__.loader = self.loader
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module.__loader__ = self.loader
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# Don't need to worry about deep-copying as trying to set an attribute
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# on an object would have triggered the load,
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# e.g. ``module.__spec__.loader = None`` would trigger a load from
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# trying to access module.__spec__.
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module.__spec__.loader_state = module.__dict__.copy()
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module.__class__ = _LazyModule
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