"""Abstract base classes related to import.""" from . import _bootstrap from . import machinery try: import _frozen_importlib except ImportError as exc: if exc.name != '_frozen_importlib': raise _frozen_importlib = None import abc import imp import marshal import sys import tokenize import warnings def _register(abstract_cls, *classes): for cls in classes: abstract_cls.register(cls) if _frozen_importlib is not None: frozen_cls = getattr(_frozen_importlib, cls.__name__) abstract_cls.register(frozen_cls) class Loader(metaclass=abc.ABCMeta): """Abstract base class for import loaders.""" @abc.abstractmethod def load_module(self, fullname): """Abstract method which when implemented should load a module. The fullname is a str.""" raise NotImplementedError @abc.abstractmethod def module_repr(self, module): """Abstract method which when implemented calculates and returns the given module's repr.""" raise NotImplementedError class Finder(metaclass=abc.ABCMeta): """Abstract base class for import finders.""" @abc.abstractmethod def find_loader(self, fullname): """Abstract method which when implemented returns a module loader. The fullname is a str. Returns a 2-tuple of (Loader, portion) where portion is a sequence of file system locations contributing to part of a namespace package. The sequence may be empty. When present, `find_loader()` is preferred over `find_module()`. """ raise NotImplementedError @abc.abstractmethod def find_module(self, fullname, path=None): """Abstract method which when implemented should find a module. The fullname is a str and the optional path is a str or None. Returns a Loader object. This method is only called if `find_loader()` is not present. """ raise NotImplementedError _register(Finder, machinery.BuiltinImporter, machinery.FrozenImporter, machinery.PathFinder, machinery.FileFinder) class ResourceLoader(Loader): """Abstract base class for loaders which can return data from their back-end storage. This ABC represents one of the optional protocols specified by PEP 302. """ @abc.abstractmethod def get_data(self, path): """Abstract method which when implemented should return the bytes for the specified path. The path must be a str.""" raise NotImplementedError class InspectLoader(Loader): """Abstract base class for loaders which support inspection about the modules they can load. This ABC represents one of the optional protocols specified by PEP 302. """ @abc.abstractmethod def is_package(self, fullname): """Abstract method which when implemented should return whether the module is a package. The fullname is a str. Returns a bool.""" raise NotImplementedError @abc.abstractmethod def get_code(self, fullname): """Abstract method which when implemented should return the code object for the module. The fullname is a str. Returns a types.CodeType.""" raise NotImplementedError @abc.abstractmethod def get_source(self, fullname): """Abstract method which should return the source code for the module. The fullname is a str. Returns a str.""" raise NotImplementedError _register(InspectLoader, machinery.BuiltinImporter, machinery.FrozenImporter, machinery.ExtensionFileLoader) class ExecutionLoader(InspectLoader): """Abstract base class for loaders that wish to support the execution of modules as scripts. This ABC represents one of the optional protocols specified in PEP 302. """ @abc.abstractmethod def get_filename(self, fullname): """Abstract method which should return the value that __file__ is to be set to.""" raise NotImplementedError class FileLoader(_bootstrap.FileLoader, ResourceLoader, ExecutionLoader): """Abstract base class partially implementing the ResourceLoader and ExecutionLoader ABCs.""" _register(FileLoader, machinery.SourceFileLoader, machinery.SourcelessFileLoader) class SourceLoader(_bootstrap.SourceLoader, ResourceLoader, ExecutionLoader): """Abstract base class for loading source code (and optionally any corresponding bytecode). To support loading from source code, the abstractmethods inherited from ResourceLoader and ExecutionLoader need to be implemented. To also support loading from bytecode, the optional methods specified directly by this ABC is required. Inherited abstractmethods not implemented in this ABC: * ResourceLoader.get_data * ExecutionLoader.get_filename """ def path_mtime(self, path): """Return the (int) modification time for the path (str).""" if self.path_stats.__func__ is SourceLoader.path_stats: raise NotImplementedError return int(self.path_stats(path)['mtime']) def path_stats(self, path): """Return a metadata dict for the source pointed to by the path (str). Possible keys: - 'mtime' (mandatory) is the numeric timestamp of last source code modification; - 'size' (optional) is the size in bytes of the source code. """ if self.path_mtime.__func__ is SourceLoader.path_mtime: raise NotImplementedError return {'mtime': self.path_mtime(path)} def set_data(self, path, data): """Write the bytes to the path (if possible). Accepts a str path and data as bytes. Any needed intermediary directories are to be created. If for some reason the file cannot be written because of permissions, fail silently. """ raise NotImplementedError _register(SourceLoader, machinery.SourceFileLoader) class PyLoader(SourceLoader): """Implement the deprecated PyLoader ABC in terms of SourceLoader. This class has been deprecated! It is slated for removal in Python 3.4. If compatibility with Python 3.1 is not needed then implement the SourceLoader ABC instead of this class. If Python 3.1 compatibility is needed, then use the following idiom to have a single class that is compatible with Python 3.1 onwards:: try: from importlib.abc import SourceLoader except ImportError: from importlib.abc import PyLoader as SourceLoader class CustomLoader(SourceLoader): def get_filename(self, fullname): # Implement ... def source_path(self, fullname): '''Implement source_path in terms of get_filename.''' try: return self.get_filename(fullname) except ImportError: return None def is_package(self, fullname): filename = os.path.basename(self.get_filename(fullname)) return os.path.splitext(filename)[0] == '__init__' """ @abc.abstractmethod def is_package(self, fullname): raise NotImplementedError @abc.abstractmethod def source_path(self, fullname): """Abstract method. Accepts a str module name and returns the path to the source code for the module.""" raise NotImplementedError def get_filename(self, fullname): """Implement get_filename in terms of source_path. As get_filename should only return a source file path there is no chance of the path not existing but loading still being possible, so ImportError should propagate instead of being turned into returning None. """ warnings.warn("importlib.abc.PyLoader is deprecated and is " "slated for removal in Python 3.4; " "use SourceLoader instead. " "See the importlib documentation on how to be " "compatible with Python 3.1 onwards.", DeprecationWarning) path = self.source_path(fullname) if path is None: raise ImportError(name=fullname) else: return path class PyPycLoader(PyLoader): """Abstract base class to assist in loading source and bytecode by requiring only back-end storage methods to be implemented. This class has been deprecated! Removal is slated for Python 3.4. Implement the SourceLoader ABC instead. If Python 3.1 compatibility is needed, see PyLoader. The methods get_code, get_source, and load_module are implemented for the user. """ def get_filename(self, fullname): """Return the source or bytecode file path.""" path = self.source_path(fullname) if path is not None: return path path = self.bytecode_path(fullname) if path is not None: return path raise ImportError("no source or bytecode path available for " "{0!r}".format(fullname), name=fullname) def get_code(self, fullname): """Get a code object from source or bytecode.""" warnings.warn("importlib.abc.PyPycLoader is deprecated and slated for " "removal in Python 3.4; use SourceLoader instead. " "If Python 3.1 compatibility is required, see the " "latest documentation for PyLoader.", DeprecationWarning) source_timestamp = self.source_mtime(fullname) # Try to use bytecode if it is available. bytecode_path = self.bytecode_path(fullname) if bytecode_path: data = self.get_data(bytecode_path) try: magic = data[:4] if len(magic) < 4: raise ImportError( "bad magic number in {}".format(fullname), name=fullname, path=bytecode_path) raw_timestamp = data[4:8] if len(raw_timestamp) < 4: raise EOFError("bad timestamp in {}".format(fullname)) pyc_timestamp = _bootstrap._r_long(raw_timestamp) raw_source_size = data[8:12] if len(raw_source_size) != 4: raise EOFError("bad file size in {}".format(fullname)) # Source size is unused as the ABC does not provide a way to # get the size of the source ahead of reading it. bytecode = data[12:] # Verify that the magic number is valid. if imp.get_magic() != magic: raise ImportError( "bad magic number in {}".format(fullname), name=fullname, path=bytecode_path) # Verify that the bytecode is not stale (only matters when # there is source to fall back on. if source_timestamp: if pyc_timestamp < source_timestamp: raise ImportError("bytecode is stale", name=fullname, path=bytecode_path) except (ImportError, EOFError): # If source is available give it a shot. if source_timestamp is not None: pass else: raise else: # Bytecode seems fine, so try to use it. return marshal.loads(bytecode) elif source_timestamp is None: raise ImportError("no source or bytecode available to create code " "object for {0!r}".format(fullname), name=fullname) # Use the source. source_path = self.source_path(fullname) if source_path is None: message = "a source path must exist to load {0}".format(fullname) raise ImportError(message, name=fullname) source = self.get_data(source_path) code_object = compile(source, source_path, 'exec', dont_inherit=True) # Generate bytecode and write it out. if not sys.dont_write_bytecode: data = bytearray(imp.get_magic()) data.extend(_bootstrap._w_long(source_timestamp)) data.extend(_bootstrap._w_long(len(source) & 0xFFFFFFFF)) data.extend(marshal.dumps(code_object)) self.write_bytecode(fullname, data) return code_object @abc.abstractmethod def source_mtime(self, fullname): """Abstract method. Accepts a str filename and returns an int modification time for the source of the module.""" raise NotImplementedError @abc.abstractmethod def bytecode_path(self, fullname): """Abstract method. Accepts a str filename and returns the str pathname to the bytecode for the module.""" raise NotImplementedError @abc.abstractmethod def write_bytecode(self, fullname, bytecode): """Abstract method. Accepts a str filename and bytes object representing the bytecode for the module. Returns a boolean representing whether the bytecode was written or not.""" raise NotImplementedError