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_bootstrap.py
"""Core implementation of import. This module is NOT meant to be directly imported! It has been designed such that it can be bootstrapped into Python as the implementation of import. As such it requires the injection of specific modules and attributes in order to work. One should use importlib as the public-facing version of this module. """ # # IMPORTANT: Whenever making changes to this module, be sure to run a top-level # `make regen-importlib` followed by `make` in order to get the frozen version # of the module updated. Not doing so will result in the Makefile to fail for # all others who don't have a ./python around to freeze the module # in the early stages of compilation. # # See importlib._setup() for what is injected into the global namespace. # When editing this code be aware that code executed at import time CANNOT # reference any injected objects! This includes not only global code but also # anything specified at the class level. def _object_name(obj): try: return obj.__qualname__ except AttributeError: return type(obj).__qualname__ # Bootstrap-related code ###################################################### # Modules injected manually by _setup() _thread = None _warnings = None _weakref = None # Import done by _install_external_importers() _bootstrap_external = None def _wrap(new, old): """Simple substitute for functools.update_wrapper.""" for replace in ['__module__', '__name__', '__qualname__', '__doc__']: if hasattr(old, replace): setattr(new, replace, getattr(old, replace)) new.__dict__.update(old.__dict__) def _new_module(name): return type(sys)(name) # Module-level locking ######################################################## # A dict mapping module names to weakrefs of _ModuleLock instances # Dictionary protected by the global import lock _module_locks = {} # A dict mapping thread ids to _ModuleLock instances _blocking_on = {} class _DeadlockError(RuntimeError): pass class _ModuleLock: """A recursive lock implementation which is able to detect deadlocks (e.g. thread 1 trying to take locks A then B, and thread 2 trying to take locks B then A). """ def __init__(self, name): self.lock = _thread.allocate_lock() self.wakeup = _thread.allocate_lock() self.name = name self.owner = None self.count = 0 self.waiters = 0 def has_deadlock(self): # Deadlock avoidance for concurrent circular imports. me = _thread.get_ident() tid = self.owner seen = set() while True: lock = _blocking_on.get(tid) if lock is None: return False tid = lock.owner if tid == me: return True if tid in seen: # bpo 38091: the chain of tid's we encounter here # eventually leads to a fixpoint or a cycle, but # does not reach 'me'. This means we would not # actually deadlock. This can happen if other # threads are at the beginning of acquire() below. return False seen.add(tid) def acquire(self): """ Acquire the module lock. If a potential deadlock is detected, a _DeadlockError is raised. Otherwise, the lock is always acquired and True is returned. """ tid = _thread.get_ident() _blocking_on[tid] = self try: while True: with self.lock: if self.count == 0 or self.owner == tid: self.owner = tid self.count += 1 return True if self.has_deadlock(): raise _DeadlockError('deadlock detected by %r' % self) if self.wakeup.acquire(False): self.waiters += 1 # Wait for a release() call self.wakeup.acquire() self.wakeup.release() finally: del _blocking_on[tid] def release(self): tid = _thread.get_ident() with self.lock: if self.owner != tid: raise RuntimeError('cannot release un-acquired lock') assert self.count > 0 self.count -= 1 if self.count == 0: self.owner = None if self.waiters: self.waiters -= 1 self.wakeup.release() def __repr__(self): return '_ModuleLock({!r}) at {}'.format(self.name, id(self)) class _DummyModuleLock: """A simple _ModuleLock equivalent for Python builds without multi-threading support.""" def __init__(self, name): self.name = name self.count = 0 def acquire(self): self.count += 1 return True def release(self): if self.count == 0: raise RuntimeError('cannot release un-acquired lock') self.count -= 1 def __repr__(self): return '_DummyModuleLock({!r}) at {}'.format(self.name, id(self)) class _ModuleLockManager: def __init__(self, name): self._name = name self._lock = None def __enter__(self): self._lock = _get_module_lock(self._name) self._lock.acquire() def __exit__(self, *args, **kwargs): self._lock.release() # The following two functions are for consumption by Python/import.c. def _get_module_lock(name): """Get or create the module lock for a given module name. Acquire/release internally the global import lock to protect _module_locks.""" _imp.acquire_lock() try: try: lock = _module_locks[name]() except KeyError: lock = None if lock is None: if _thread is None: lock = _DummyModuleLock(name) else: lock = _ModuleLock(name) def cb(ref, name=name): _imp.acquire_lock() try: # bpo-31070: Check if another thread created a new lock # after the previous lock was destroyed # but before the weakref callback was called. if _module_locks.get(name) is ref: del _module_locks[name] finally: _imp.release_lock() _module_locks[name] = _weakref.ref(lock, cb) finally: _imp.release_lock() return lock def _lock_unlock_module(name): """Acquires then releases the module lock for a given module name. This is used to ensure a module is completely initialized, in the event it is being imported by another thread. """ lock = _get_module_lock(name) try: lock.acquire() except _DeadlockError: # Concurrent circular import, we'll accept a partially initialized # module object. pass else: lock.release() # Frame stripping magic ############################################### def _call_with_frames_removed(f, *args, **kwds): """remove_importlib_frames in import.c will always remove sequences of importlib frames that end with a call to this function Use it instead of a normal call in places where including the importlib frames introduces unwanted noise into the traceback (e.g. when executing module code) """ return f(*args, **kwds) def _verbose_message(message, *args, verbosity=1): """Print the message to stderr if -v/PYTHONVERBOSE is turned on.""" if sys.flags.verbose >= verbosity: if not message.startswith(('#', 'import ')): message = '# ' + message print(message.format(*args), file=sys.stderr) def _requires_builtin(fxn): """Decorator to verify the named module is built-in.""" def _requires_builtin_wrapper(self, fullname): if fullname not in sys.builtin_module_names: raise ImportError('{!r} is not a built-in module'.format(fullname), name=fullname) return fxn(self, fullname) _wrap(_requires_builtin_wrapper, fxn) return _requires_builtin_wrapper def _requires_frozen(fxn): """Decorator to verify the named module is frozen.""" def _requires_frozen_wrapper(self, fullname): if not _imp.is_frozen(fullname): raise ImportError('{!r} is not a frozen module'.format(fullname), name=fullname) return fxn(self, fullname) _wrap(_requires_frozen_wrapper, fxn) return _requires_frozen_wrapper # Typically used by loader classes as a method replacement. def _load_module_shim(self, fullname): """Load the specified module into sys.modules and return it. This method is deprecated. Use loader.exec_module() instead. """ msg = ("the load_module() method is deprecated and slated for removal in " "Python 3.12; use exec_module() instead") _warnings.warn(msg, DeprecationWarning) spec = spec_from_loader(fullname, self) if fullname in sys.modules: module = sys.modules[fullname] _exec(spec, module) return sys.modules[fullname] else: return _load(spec) # Module specifications ####################################################### def _module_repr(module): """The implementation of ModuleType.__repr__().""" loader = getattr(module, '__loader__', None) if spec := getattr(module, "__spec__", None): return _module_repr_from_spec(spec) elif hasattr(loader, 'module_repr'): try: return loader.module_repr(module) except Exception: pass # Fall through to a catch-all which always succeeds. try: name = module.__name__ except AttributeError: name = '?' try: filename = module.__file__ except AttributeError: if loader is None: return '<module {!r}>'.format(name) else: return '<module {!r} ({!r})>'.format(name, loader) else: return '<module {!r} from {!r}>'.format(name, filename) class ModuleSpec: """The specification for a module, used for loading. A module's spec is the source for information about the module. For data associated with the module, including source, use the spec's loader. `name` is the absolute name of the module. `loader` is the loader to use when loading the module. `parent` is the name of the package the module is in. The parent is derived from the name. `is_package` determines if the module is considered a package or not. On modules this is reflected by the `__path__` attribute. `origin` is the specific location used by the loader from which to load the module, if that information is available. When filename is set, origin will match. `has_location` indicates that a spec's "origin" reflects a location. When this is True, `__file__` attribute of the module is set. `cached` is the location of the cached bytecode file, if any. It corresponds to the `__cached__` attribute. `submodule_search_locations` is the sequence of path entries to search when importing submodules. If set, is_package should be True--and False otherwise. Packages are simply modules that (may) have submodules. If a spec has a non-None value in `submodule_search_locations`, the import system will consider modules loaded from the spec as packages. Only finders (see importlib.abc.MetaPathFinder and importlib.abc.PathEntryFinder) should modify ModuleSpec instances. """ def __init__(self, name, loader, *, origin=None, loader_state=None, is_package=None): self.name = name self.loader = loader self.origin = origin self.loader_state = loader_state self.submodule_search_locations = [] if is_package else None self._uninitialized_submodules = [] # file-location attributes self._set_fileattr = False self._cached = None def __repr__(self): args = ['name={!r}'.format(self.name), 'loader={!r}'.format(self.loader)] if self.origin is not None: args.append('origin={!r}'.format(self.origin)) if self.submodule_search_locations is not None: args.append('submodule_search_locations={}' .format(self.submodule_search_locations)) return '{}({})'.format(self.__class__.__name__, ', '.join(args)) def __eq__(self, other): smsl = self.submodule_search_locations try: return (self.name == other.name and self.loader == other.loader and self.origin == other.origin and smsl == other.submodule_search_locations and self.cached == other.cached and self.has_location == other.has_location) except AttributeError: return NotImplemented @property def cached(self): if self._cached is None: if self.origin is not None and self._set_fileattr: if _bootstrap_external is None: raise NotImplementedError self._cached = _bootstrap_external._get_cached(self.origin) return self._cached @cached.setter def cached(self, cached): self._cached = cached @property def parent(self): """The name of the module's parent.""" if self.submodule_search_locations is None: return self.name.rpartition('.')[0] else: return self.name @property def has_location(self): return self._set_fileattr @has_location.setter def has_location(self, value): self._set_fileattr = bool(value) def spec_from_loader(name, loader, *, origin=None, is_package=None): """Return a module spec based on various loader methods.""" if origin is None: origin = getattr(loader, '_ORIGIN', None) if not origin and hasattr(loader, 'get_filename'): if _bootstrap_external is None: raise NotImplementedError spec_from_file_location = _bootstrap_external.spec_from_file_location if is_package is None: return spec_from_file_location(name, loader=loader) search = [] if is_package else None return spec_from_file_location(name, loader=loader, submodule_search_locations=search) if is_package is None: if hasattr(loader, 'is_package'): try: is_package = loader.is_package(name) except ImportError: is_package = None # aka, undefined else: # the default is_package = False return ModuleSpec(name, loader, origin=origin, is_package=is_package) def _spec_from_module(module, loader=None, origin=None): # This function is meant for use in _setup(). try: spec = module.__spec__ except AttributeError: pass else: if spec is not None: return spec name = module.__name__ if loader is None: try: loader = module.__loader__ except AttributeError: # loader will stay None. pass try: location = module.__file__ except AttributeError: location = None if origin is None: if loader is not None: origin = getattr(loader, '_ORIGIN', None) if not origin and location is not None: origin = location try: cached = module.__cached__ except AttributeError: cached = None try: submodule_search_locations = list(module.__path__) except AttributeError: submodule_search_locations = None spec = ModuleSpec(name, loader, origin=origin) spec._set_fileattr = False if location is None else (origin == location) spec.cached = cached spec.submodule_search_locations = submodule_search_locations return spec def _init_module_attrs(spec, module, *, override=False): # The passed-in module may be not support attribute assignment, # in which case we simply don't set the attributes. # __name__ if (override or getattr(module, '__name__', None) is None): try: module.__name__ = spec.name except AttributeError: pass # __loader__ if override or getattr(module, '__loader__', None) is None: loader = spec.loader if loader is None: # A backward compatibility hack. if spec.submodule_search_locations is not None: if _bootstrap_external is None: raise NotImplementedError NamespaceLoader = _bootstrap_external.NamespaceLoader loader = NamespaceLoader.__new__(NamespaceLoader) loader._path = spec.submodule_search_locations spec.loader = loader # While the docs say that module.__file__ is not set for # built-in modules, and the code below will avoid setting it if # spec.has_location is false, this is incorrect for namespace # packages. Namespace packages have no location, but their # __spec__.origin is None, and thus their module.__file__ # should also be None for consistency. While a bit of a hack, # this is the best place to ensure this consistency. # # See # https://docs.python.org/3/library/importlib.html#importlib.abc.Loader.load_module # and bpo-32305 module.__file__ = None try: module.__loader__ = loader except AttributeError: pass # __package__ if override or getattr(module, '__package__', None) is None: try: module.__package__ = spec.parent except AttributeError: pass # __spec__ try: module.__spec__ = spec except AttributeError: pass # __path__ if override or getattr(module, '__path__', None) is None: if spec.submodule_search_locations is not None: # XXX We should extend __path__ if it's already a list. try: module.__path__ = spec.submodule_search_locations except AttributeError: pass # __file__/__cached__ if spec.has_location: if override or getattr(module, '__file__', None) is None: try: module.__file__ = spec.origin except AttributeError: pass if override or getattr(module, '__cached__', None) is None: if spec.cached is not None: try: module.__cached__ = spec.cached except AttributeError: pass return module def module_from_spec(spec): """Create a module based on the provided spec.""" # Typically loaders will not implement create_module(). module = None if hasattr(spec.loader, 'create_module'): # If create_module() returns `None` then it means default # module creation should be used. module = spec.loader.create_module(spec) elif hasattr(spec.loader, 'exec_module'): raise ImportError('loaders that define exec_module() ' 'must also define create_module()') if module is None: module = _new_module(spec.name) _init_module_attrs(spec, module) return module def _module_repr_from_spec(spec): """Return the repr to use for the module.""" # We mostly replicate _module_repr() using the spec attributes. name = '?' if spec.name is None else spec.name if spec.origin is None: if spec.loader is None: return '<module {!r}>'.format(name) else: return '<module {!r} ({!r})>'.format(name, spec.loader) else: if spec.has_location: return '<module {!r} from {!r}>'.format(name, spec.origin) else: return '<module {!r} ({})>'.format(spec.name, spec.origin) # Used by importlib.reload() and _load_module_shim(). def _exec(spec, module): """Execute the spec's specified module in an existing module's namespace.""" name = spec.name with _ModuleLockManager(name): if sys.modules.get(name) is not module: msg = 'module {!r} not in sys.modules'.format(name) raise ImportError(msg, name=name) try: if spec.loader is None: if spec.submodule_search_locations is None: raise ImportError('missing loader', name=spec.name) # Namespace package. _init_module_attrs(spec, module, override=True) else: _init_module_attrs(spec, module, override=True) if not hasattr(spec.loader, 'exec_module'): msg = (f"{_object_name(spec.loader)}.exec_module() not found; " "falling back to load_module()") _warnings.warn(msg, ImportWarning) spec.loader.load_module(name) else: spec.loader.exec_module(module) finally: # Update the order of insertion into sys.modules for module # clean-up at shutdown. module = sys.modules.pop(spec.name) sys.modules[spec.name] = module return module def _load_backward_compatible(spec): # It is assumed that all callers have been warned about using load_module() # appropriately before calling this function. try: spec.loader.load_module(spec.name) except: if spec.name in sys.modules: module = sys.modules.pop(spec.name) sys.modules[spec.name] = module raise # The module must be in sys.modules at this point! # Move it to the end of sys.modules. module = sys.modules.pop(spec.name) sys.modules[spec.name] = module if getattr(module, '__loader__', None) is None: try: module.__loader__ = spec.loader except AttributeError: pass if getattr(module, '__package__', None) is None: try: # Since module.__path__ may not line up with # spec.submodule_search_paths, we can't necessarily rely # on spec.parent here. module.__package__ = module.__name__ if not hasattr(module, '__path__'): module.__package__ = spec.name.rpartition('.')[0] except AttributeError: pass if getattr(module, '__spec__', None) is None: try: module.__spec__ = spec except AttributeError: pass return module def _load_unlocked(spec): # A helper for direct use by the import system. if spec.loader is not None: # Not a namespace package. if not hasattr(spec.loader, 'exec_module'): msg = (f"{_object_name(spec.loader)}.exec_module() not found; " "falling back to load_module()") _warnings.warn(msg, ImportWarning) return _load_backward_compatible(spec) module = module_from_spec(spec) # This must be done before putting the module in sys.modules # (otherwise an optimization shortcut in import.c becomes # wrong). spec._initializing = True try: sys.modules[spec.name] = module try: if spec.loader is None: if spec.submodule_search_locations is None: raise ImportError('missing loader', name=spec.name) # A namespace package so do nothing. else: spec.loader.exec_module(module) except: try: del sys.modules[spec.name] except KeyError: pass raise # Move the module to the end of sys.modules. # We don't ensure that the import-related module attributes get # set in the sys.modules replacement case. Such modules are on # their own. module = sys.modules.pop(spec.name) sys.modules[spec.name] = module _verbose_message('import {!r} # {!r}', spec.name, spec.loader) finally: spec._initializing = False return module # A method used during testing of _load_unlocked() and by # _load_module_shim(). def _load(spec): """Return a new module object, loaded by the spec's loader. The module is not added to its parent. If a module is already in sys.modules, that existing module gets clobbered. """ with _ModuleLockManager(spec.name): return _load_unlocked(spec) # Loaders ##################################################################### class BuiltinImporter: """Meta path import for built-in modules. All methods are either class or static methods to avoid the need to instantiate the class. """ _ORIGIN = "built-in" @staticmethod def module_repr(module): """Return repr for the module. The method is deprecated. The import machinery does the job itself. """ _warnings.warn("BuiltinImporter.module_repr() is deprecated and " "slated for removal in Python 3.12", DeprecationWarning) return f'<module {module.__name__!r} ({BuiltinImporter._ORIGIN})>' @classmethod def find_spec(cls, fullname, path=None, target=None): if _imp.is_builtin(fullname): return spec_from_loader(fullname, cls, origin=cls._ORIGIN) else: return None @classmethod def find_module(cls, fullname, path=None): """Find the built-in module. If 'path' is ever specified then the search is considered a failure. This method is deprecated. Use find_spec() instead. """ _warnings.warn("BuiltinImporter.find_module() is deprecated and " "slated for removal in Python 3.12; use find_spec() instead", DeprecationWarning) spec = cls.find_spec(fullname, path) return spec.loader if spec is not None else None @staticmethod def create_module(spec): """Create a built-in module""" if spec.name not in sys.builtin_module_names: raise ImportError('{!r} is not a built-in module'.format(spec.name), name=spec.name) return _call_with_frames_removed(_imp.create_builtin, spec) @staticmethod def exec_module(module): """Exec a built-in module""" _call_with_frames_removed(_imp.exec_builtin, module) @classmethod @_requires_builtin def get_code(cls, fullname): """Return None as built-in modules do not have code objects.""" return None @classmethod @_requires_builtin def get_source(cls, fullname): """Return None as built-in modules do not have source code.""" return None @classmethod @_requires_builtin def is_package(cls, fullname): """Return False as built-in modules are never packages.""" return False load_module = classmethod(_load_module_shim) class FrozenImporter: """Meta path import for frozen modules. All methods are either class or static methods to avoid the need to instantiate the class. """ _ORIGIN = "frozen" @staticmethod def module_repr(m): """Return repr for the module. The method is deprecated. The import machinery does the job itself. """ _warnings.warn("FrozenImporter.module_repr() is deprecated and " "slated for removal in Python 3.12", DeprecationWarning) return '<module {!r} ({})>'.format(m.__name__, FrozenImporter._ORIGIN) @classmethod def _fix_up_module(cls, module): spec = module.__spec__ state = spec.loader_state if state is None: # The module is missing FrozenImporter-specific values. # Fix up the spec attrs. origname = vars(module).pop('__origname__', None) assert origname, 'see PyImport_ImportFrozenModuleObject()' ispkg = hasattr(module, '__path__') assert _imp.is_frozen_package(module.__name__) == ispkg, ispkg filename, pkgdir = cls._resolve_filename(origname, spec.name, ispkg) spec.loader_state = type(sys.implementation)( filename=filename, origname=origname, ) __path__ = spec.submodule_search_locations if ispkg: assert __path__ == [], __path__ if pkgdir: spec.submodule_search_locations.insert(0, pkgdir) else: assert __path__ is None, __path__ # Fix up the module attrs (the bare minimum). assert not hasattr(module, '__file__'), module.__file__ if filename: try: module.__file__ = filename except AttributeError: pass if ispkg: if module.__path__ != __path__: assert module.__path__ == [], module.__path__ module.__path__.extend(__path__) else: # These checks ensure that _fix_up_module() is only called # in the right places. __path__ = spec.submodule_search_locations ispkg = __path__ is not None # Check the loader state. assert sorted(vars(state)) == ['filename', 'origname'], state if state.origname: # The only frozen modules with "origname" set are stdlib modules. (__file__, pkgdir, ) = cls._resolve_filename(state.origname, spec.name, ispkg) assert state.filename == __file__, (state.filename, __file__) if pkgdir: assert __path__ == [pkgdir], (__path__, pkgdir) else: assert __path__ == ([] if ispkg else None), __path__ else: __file__ = None assert state.filename is None, state.filename assert __path__ == ([] if ispkg else None), __path__ # Check the file attrs. if __file__: assert hasattr(module, '__file__') assert module.__file__ == __file__, (module.__file__, __file__) else: assert not hasattr(module, '__file__'), module.__file__ if ispkg: assert hasattr(module, '__path__') assert module.__path__ == __path__, (module.__path__, __path__) else: assert not hasattr(module, '__path__'), module.__path__ assert not spec.has_location @classmethod def _resolve_filename(cls, fullname, alias=None, ispkg=False): if not fullname or not getattr(sys, '_stdlib_dir', None): return None, None try: sep = cls._SEP except AttributeError: sep = cls._SEP = '\\' if sys.platform == 'win32' else '/' if fullname != alias: if fullname.startswith('<'): fullname = fullname[1:] if not ispkg: fullname = f'{fullname}.__init__' else: ispkg = False relfile = fullname.replace('.', sep) if ispkg: pkgdir = f'{sys._stdlib_dir}{sep}{relfile}' filename = f'{pkgdir}{sep}__init__.py' else: pkgdir = None filename = f'{sys._stdlib_dir}{sep}{relfile}.py' return filename, pkgdir @classmethod def find_spec(cls, fullname, path=None, target=None): info = _call_with_frames_removed(_imp.find_frozen, fullname) if info is None: return None # We get the marshaled data in exec_module() (the loader # part of the importer), instead of here (the finder part). # The loader is the usual place to get the data that will # be loaded into the module. (For example, see _LoaderBasics # in _bootstra_external.py.) Most importantly, this importer # is simpler if we wait to get the data. # However, getting as much data in the finder as possible # to later load the module is okay, and sometimes important. # (That's why ModuleSpec.loader_state exists.) This is # especially true if it avoids throwing away expensive data # the loader would otherwise duplicate later and can be done # efficiently. In this case it isn't worth it. _, ispkg, origname = info spec = spec_from_loader(fullname, cls, origin=cls._ORIGIN, is_package=ispkg) filename, pkgdir = cls._resolve_filename(origname, fullname, ispkg) spec.loader_state = type(sys.implementation)( filename=filename, origname=origname, ) if pkgdir: spec.submodule_search_locations.insert(0, pkgdir) return spec @classmethod def find_module(cls, fullname, path=None): """Find a frozen module. This method is deprecated. Use find_spec() instead. """ _warnings.warn("FrozenImporter.find_module() is deprecated and " "slated for removal in Python 3.12; use find_spec() instead", DeprecationWarning) return cls if _imp.is_frozen(fullname) else None @staticmethod def create_module(spec): """Set __file__, if able.""" module = _new_module(spec.name) try: filename = spec.loader_state.filename except AttributeError: pass else: if filename: module.__file__ = filename return module @staticmethod def exec_module(module): spec = module.__spec__ name = spec.name code = _call_with_frames_removed(_imp.get_frozen_object, name) exec(code, module.__dict__) @classmethod def load_module(cls, fullname): """Load a frozen module. This method is deprecated. Use exec_module() instead. """ # Warning about deprecation implemented in _load_module_shim(). module = _load_module_shim(cls, fullname) info = _imp.find_frozen(fullname) assert info is not None _, ispkg, origname = info module.__origname__ = origname vars(module).pop('__file__', None) if ispkg: module.__path__ = [] cls._fix_up_module(module) return module @classmethod @_requires_frozen def get_code(cls, fullname): """Return the code object for the frozen module.""" return _imp.get_frozen_object(fullname) @classmethod @_requires_frozen def get_source(cls, fullname): """Return None as frozen modules do not have source code.""" return None @classmethod @_requires_frozen def is_package(cls, fullname): """Return True if the frozen module is a package.""" return _imp.is_frozen_package(fullname) # Import itself ############################################################### class _ImportLockContext: """Context manager for the import lock.""" def __enter__(self): """Acquire the import lock.""" _imp.acquire_lock() def __exit__(self, exc_type, exc_value, exc_traceback): """Release the import lock regardless of any raised exceptions.""" _imp.release_lock() def _resolve_name(name, package, level): """Resolve a relative module name to an absolute one.""" bits = package.rsplit('.', level - 1) if len(bits) < level: raise ImportError('attempted relative import beyond top-level package') base = bits[0] return '{}.{}'.format(base, name) if name else base def _find_spec_legacy(finder, name, path): msg = (f"{_object_name(finder)}.find_spec() not found; " "falling back to find_module()") _warnings.warn(msg, ImportWarning) loader = finder.find_module(name, path) if loader is None: return None return spec_from_loader(name, loader) def _find_spec(name, path, target=None): """Find a module's spec.""" meta_path = sys.meta_path if meta_path is None: # PyImport_Cleanup() is running or has been called. raise ImportError("sys.meta_path is None, Python is likely " "shutting down") if not meta_path: _warnings.warn('sys.meta_path is empty', ImportWarning) # We check sys.modules here for the reload case. While a passed-in # target will usually indicate a reload there is no guarantee, whereas # sys.modules provides one. is_reload = name in sys.modules for finder in meta_path: with _ImportLockContext(): try: find_spec = finder.find_spec except AttributeError: spec = _find_spec_legacy(finder, name, path) if spec is None: continue else: spec = find_spec(name, path, target) if spec is not None: # The parent import may have already imported this module. if not is_reload and name in sys.modules: module = sys.modules[name] try: __spec__ = module.__spec__ except AttributeError: # We use the found spec since that is the one that # we would have used if the parent module hadn't # beaten us to the punch. return spec else: if __spec__ is None: return spec else: return __spec__ else: return spec else: return None def _sanity_check(name, package, level): """Verify arguments are "sane".""" if not isinstance(name, str): raise TypeError('module name must be str, not {}'.format(type(name))) if level < 0: raise ValueError('level must be >= 0') if level > 0: if not isinstance(package, str): raise TypeError('__package__ not set to a string') elif not package: raise ImportError('attempted relative import with no known parent ' 'package') if not name and level == 0: raise ValueError('Empty module name') _ERR_MSG_PREFIX = 'No module named ' _ERR_MSG = _ERR_MSG_PREFIX + '{!r}' def _find_and_load_unlocked(name, import_): path = None parent = name.rpartition('.')[0] parent_spec = None if parent: if parent not in sys.modules: _call_with_frames_removed(import_, parent) # Crazy side-effects! if name in sys.modules: return sys.modules[name] parent_module = sys.modules[parent] try: path = parent_module.__path__ except AttributeError: msg = (_ERR_MSG + '; {!r} is not a package').format(name, parent) raise ModuleNotFoundError(msg, name=name) from None parent_spec = parent_module.__spec__ child = name.rpartition('.')[2] spec = _find_spec(name, path) if spec is None: raise ModuleNotFoundError(_ERR_MSG.format(name), name=name) else: if parent_spec: # Temporarily add child we are currently importing to parent's # _uninitialized_submodules for circular import tracking. parent_spec._uninitialized_submodules.append(child) try: module = _load_unlocked(spec) finally: if parent_spec: parent_spec._uninitialized_submodules.pop() if parent: # Set the module as an attribute on its parent. parent_module = sys.modules[parent] try: setattr(parent_module, child, module) except AttributeError: msg = f"Cannot set an attribute on {parent!r} for child module {child!r}" _warnings.warn(msg, ImportWarning) return module _NEEDS_LOADING = object() def _find_and_load(name, import_): """Find and load the module.""" # Optimization: we avoid unneeded module locking if the module # already exists in sys.modules and is fully initialized. module = sys.modules.get(name, _NEEDS_LOADING) if (module is _NEEDS_LOADING or getattr(getattr(module, "__spec__", None), "_initializing", False)): with _ModuleLockManager(name): module = sys.modules.get(name, _NEEDS_LOADING) if module is _NEEDS_LOADING: return _find_and_load_unlocked(name, import_) # Optimization: only call _bootstrap._lock_unlock_module() if # module.__spec__._initializing is True. # NOTE: because of this, initializing must be set *before* # putting the new module in sys.modules. _lock_unlock_module(name) if module is None: message = ('import of {} halted; ' 'None in sys.modules'.format(name)) raise ModuleNotFoundError(message, name=name) return module def _gcd_import(name, package=None, level=0): """Import and return the module based on its name, the package the call is being made from, and the level adjustment. This function represents the greatest common denominator of functionality between import_module and __import__. This includes setting __package__ if the loader did not. """ _sanity_check(name, package, level) if level > 0: name = _resolve_name(name, package, level) return _find_and_load(name, _gcd_import) def _handle_fromlist(module, fromlist, import_, *, recursive=False): """Figure out what __import__ should return. The import_ parameter is a callable which takes the name of module to import. It is required to decouple the function from assuming importlib's import implementation is desired. """ # The hell that is fromlist ... # If a package was imported, try to import stuff from fromlist. for x in fromlist: if not isinstance(x, str): if recursive: where = module.__name__ + '.__all__' else: where = "``from list''" raise TypeError(f"Item in {where} must be str, " f"not {type(x).__name__}") elif x == '*': if not recursive and hasattr(module, '__all__'): _handle_fromlist(module, module.__all__, import_, recursive=True) elif not hasattr(module, x): from_name = '{}.{}'.format(module.__name__, x) try: _call_with_frames_removed(import_, from_name) except ModuleNotFoundError as exc: # Backwards-compatibility dictates we ignore failed # imports triggered by fromlist for modules that don't # exist. if (exc.name == from_name and sys.modules.get(from_name, _NEEDS_LOADING) is not None): continue raise return module def _calc___package__(globals): """Calculate what __package__ should be. __package__ is not guaranteed to be defined or could be set to None to represent that its proper value is unknown. """ package = globals.get('__package__') spec = globals.get('__spec__') if package is not None: if spec is not None and package != spec.parent: _warnings.warn("__package__ != __spec__.parent " f"({package!r} != {spec.parent!r})", ImportWarning, stacklevel=3) return package elif spec is not None: return spec.parent else: _warnings.warn("can't resolve package from __spec__ or __package__, " "falling back on __name__ and __path__", ImportWarning, stacklevel=3) package = globals['__name__'] if '__path__' not in globals: package = package.rpartition('.')[0] return package def __import__(name, globals=None, locals=None, fromlist=(), level=0): """Import a module. The 'globals' argument is used to infer where the import is occurring from to handle relative imports. The 'locals' argument is ignored. The 'fromlist' argument specifies what should exist as attributes on the module being imported (e.g. ``from module import <fromlist>``). The 'level' argument represents the package location to import from in a relative import (e.g. ``from ..pkg import mod`` would have a 'level' of 2). """ if level == 0: module = _gcd_import(name) else: globals_ = globals if globals is not None else {} package = _calc___package__(globals_) module = _gcd_import(name, package, level) if not fromlist: # Return up to the first dot in 'name'. This is complicated by the fact # that 'name' may be relative. if level == 0: return _gcd_import(name.partition('.')[0]) elif not name: return module else: # Figure out where to slice the module's name up to the first dot # in 'name'. cut_off = len(name) - len(name.partition('.')[0]) # Slice end needs to be positive to alleviate need to special-case # when ``'.' not in name``. return sys.modules[module.__name__[:len(module.__name__)-cut_off]] elif hasattr(module, '__path__'): return _handle_fromlist(module, fromlist, _gcd_import) else: return module def _builtin_from_name(name): spec = BuiltinImporter.find_spec(name) if spec is None: raise ImportError('no built-in module named ' + name) return _load_unlocked(spec) def _setup(sys_module, _imp_module): """Setup importlib by importing needed built-in modules and injecting them into the global namespace. As sys is needed for sys.modules access and _imp is needed to load built-in modules, those two modules must be explicitly passed in. """ global _imp, sys _imp = _imp_module sys = sys_module # Set up the spec for existing builtin/frozen modules. module_type = type(sys) for name, module in sys.modules.items(): if isinstance(module, module_type): if name in sys.builtin_module_names: loader = BuiltinImporter elif _imp.is_frozen(name): loader = FrozenImporter else: continue spec = _spec_from_module(module, loader) _init_module_attrs(spec, module) if loader is FrozenImporter: loader._fix_up_module(module) # Directly load built-in modules needed during bootstrap. self_module = sys.modules[__name__] for builtin_name in ('_thread', '_warnings', '_weakref'): if builtin_name not in sys.modules: builtin_module = _builtin_from_name(builtin_name) else: builtin_module = sys.modules[builtin_name] setattr(self_module, builtin_name, builtin_module) def _install(sys_module, _imp_module): """Install importers for builtin and frozen modules""" _setup(sys_module, _imp_module) sys.meta_path.append(BuiltinImporter) sys.meta_path.append(FrozenImporter) def _install_external_importers(): """Install importers that require external filesystem access""" global _bootstrap_external import _frozen_importlib_external _bootstrap_external = _frozen_importlib_external _frozen_importlib_external._install(sys.modules[__name__])
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