"""Abstract base classes related to import."""

from . import _bootstrap_external

from . import machinery

try:

import _frozen_importlib

except ImportError as exc:

if exc.name != '_frozen_importlib':

raise

_frozen_importlib = None

try:

import _frozen_importlib_external

except ImportError:

_frozen_importlib_external = _bootstrap_external

from ._abc import Loader

import abc

__all__ = [

'Loader', 'MetaPathFinder', 'PathEntryFinder',

'ResourceLoader', 'InspectLoader', 'ExecutionLoader',

'FileLoader', 'SourceLoader',

]

def _register(abstract_cls, *classes):

for cls in classes:

abstract_cls.register(cls)

if _frozen_importlib is not None:

try:

frozen_cls = getattr(_frozen_importlib, cls.__name__)

except AttributeError:

frozen_cls = getattr(_frozen_importlib_external, cls.__name__)

abstract_cls.register(frozen_cls)

class MetaPathFinder(metaclass=abc.ABCMeta):

"""Abstract base class for import finders on sys.meta_path."""

# We don't define find_spec() here since that would break

# hasattr checks we do to support backward compatibility.

def invalidate_caches(self):

"""An optional method for clearing the finder's cache, if any.

This method is used by importlib.invalidate_caches().

"""

def discover(self, parent=None):

"""An optional method which searches for possible specs with given *parent*

module spec. If *parent* is *None*, MetaPathFinder.discover will search

for top-level modules.

Returns an iterable of possible specs.

"""

return ()

_register(MetaPathFinder, machinery.BuiltinImporter, machinery.FrozenImporter,

machinery.PathFinder, machinery.WindowsRegistryFinder)

class PathEntryFinder(metaclass=abc.ABCMeta):

"""Abstract base class for path entry finders used by PathFinder."""

def invalidate_caches(self):

"""An optional method for clearing the finder's cache, if any.

This method is used by PathFinder.invalidate_caches().

"""

def discover(self, parent=None):

"""An optional method which searches for possible specs with given

*parent* module spec. If *parent* is *None*, PathEntryFinder.discover

will search for top-level modules.

Returns an iterable of possible specs.

"""

return ()

_register(PathEntryFinder, machinery.FileFinder)

class ResourceLoader(Loader):

"""Abstract base class for loaders which can return data from their

back-end storage to facilitate reading data to perform an import.

This ABC represents one of the optional protocols specified by PEP 302.

For directly loading resources, use TraversableResources instead. This class

primarily exists for backwards compatibility with other ABCs in this module.

"""

@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 OSError

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.

"""

def is_package(self, fullname):

"""Optional method which when implemented should return whether the

module is a package. The fullname is a str. Returns a bool.

Raises ImportError if the module cannot be found.

"""

raise ImportError

def get_code(self, fullname):

"""Method which returns the code object for the module.

The fullname is a str. Returns a types.CodeType if possible, else

returns None if a code object does not make sense

(e.g. built-in module). Raises ImportError if the module cannot be

found.

"""

source = self.get_source(fullname)

if source is None:

return None

return self.source_to_code(source, '<string>', fullname)

@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.

Raises ImportError if the module cannot be found.

"""

raise ImportError

@staticmethod

def source_to_code(data, path='<string>', fullname=None):

"""Compile 'data' into a code object.

The 'data' argument can be anything that compile() can handle. The'path'

argument should be where the data was retrieved (when applicable)."""

return compile(data, path, 'exec', dont_inherit=True, module=fullname)

exec_module = _bootstrap_external._LoaderBasics.exec_module

_register(InspectLoader, machinery.BuiltinImporter, machinery.FrozenImporter, machinery.NamespaceLoader)

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.

Raises ImportError if the module cannot be found.

"""

raise ImportError

def get_code(self, fullname):

"""Method to return the code object for fullname.

Should return None if not applicable (e.g. built-in module).

Raise ImportError if the module cannot be found.

"""

source = self.get_source(fullname)

if source is None:

return None

try:

path = self.get_filename(fullname)

except ImportError:

path = '<string>'

return self.source_to_code(source, path, fullname)

_register(

ExecutionLoader,

machinery.ExtensionFileLoader,

machinery.AppleFrameworkLoader,

)

class FileLoader(_bootstrap_external.FileLoader, ResourceLoader, ExecutionLoader):

"""Abstract base class partially implementing the ResourceLoader and

ExecutionLoader ABCs."""

_register(FileLoader, machinery.SourceFileLoader,

machinery.SourcelessFileLoader)

class SourceLoader(_bootstrap_external.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)."""

import warnings

warnings.warn('SourceLoader.path_mtime is deprecated in favour of '

'SourceLoader.path_stats().',

DeprecationWarning, stacklevel=2)

if self.path_stats.__func__ is SourceLoader.path_stats:

raise OSError

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 OSError

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.

"""

_register(SourceLoader, machinery.SourceFileLoader)