Staging
v0.5.1
v0.5.1
https://github.com/python/cpython
Tip revision: a58a626092151ed73e2e0382ff63bd0c7dca4a14 authored by Benjamin Peterson on 07 March 2009, 16:34:40 UTC
bump version to 3.1a1
bump version to 3.1a1
Tip revision: a58a626
_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.
"""
# Injected modules are '_warnings', 'imp', 'sys', 'marshal', 'errno', '_io',
# and '_os' (a.k.a. 'posix', 'nt' or 'os2').
# Injected attribute is path_sep.
#
# 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.
# XXX Could also expose Modules/getpath.c:joinpath()
def _path_join(*args):
"""Replacement for os.path.join."""
return path_sep.join(x[:-len(path_sep)] if x.endswith(path_sep) else x
for x in args)
def _path_exists(path):
"""Replacement for os.path.exists."""
try:
_os.stat(path)
except OSError:
return False
else:
return True
def _path_is_mode_type(path, mode):
"""Test whether the path is the specified mode type."""
try:
stat_info = _os.stat(path)
except OSError:
return False
return (stat_info.st_mode & 0o170000) == mode
# XXX Could also expose Modules/getpath.c:isfile()
def _path_isfile(path):
"""Replacement for os.path.isfile."""
return _path_is_mode_type(path, 0o100000)
# XXX Could also expose Modules/getpath.c:isdir()
def _path_isdir(path):
"""Replacement for os.path.isdir."""
return _path_is_mode_type(path, 0o040000)
def _path_without_ext(path, ext_type):
"""Replacement for os.path.splitext()[0]."""
for suffix in suffix_list(ext_type):
if path.endswith(suffix):
return path[:-len(suffix)]
else:
raise ValueError("path is not of the specified type")
def _path_absolute(path):
"""Replacement for os.path.abspath."""
if not path:
path = _os.getcwd()
try:
return _os._getfullpathname(path)
except AttributeError:
if path.startswith('/'):
return path
else:
return _path_join(_os.getcwd(), path)
class closing:
"""Simple replacement for contextlib.closing."""
def __init__(self, obj):
self.obj = obj
def __enter__(self):
return self.obj
def __exit__(self, *args):
self.obj.close()
def wrap(new, old):
"""Simple substitute for functools.wraps."""
for replace in ['__module__', '__name__', '__doc__']:
setattr(new, replace, getattr(old, replace))
new.__dict__.update(old.__dict__)
def set_package(fxn):
"""Set __package__ on the returned module."""
def wrapper(*args, **kwargs):
module = fxn(*args, **kwargs)
if not hasattr(module, '__package__') or module.__package__ is None:
module.__package__ = module.__name__
if not hasattr(module, '__path__'):
module.__package__ = module.__package__.rpartition('.')[0]
return module
wrap(wrapper, fxn)
return wrapper
class BuiltinImporter:
"""Meta path loader for built-in modules.
All methods are either class or static methods, allowing direct use of the
class.
"""
@classmethod
def find_module(cls, fullname, path=None):
"""Try to find the built-in module.
If 'path' is ever specified then the search is considered a failure.
"""
if path is not None:
return None
return cls if imp.is_builtin(fullname) else None
@classmethod
@set_package
def load_module(cls, fullname):
"""Load a built-in module."""
if fullname not in sys.builtin_module_names:
raise ImportError("{0} is not a built-in module".format(fullname))
is_reload = fullname in sys.modules
try:
return imp.init_builtin(fullname)
except:
if not is_reload and fullname in sys.modules:
del sys.modules[fullname]
raise
class FrozenImporter:
"""Meta path class for importing frozen modules.
All methods are either class or static method to allow direct use of the
class.
"""
@classmethod
def find_module(cls, fullname, path=None):
"""Find a frozen module."""
return cls if imp.is_frozen(fullname) else None
@classmethod
@set_package
def load_module(cls, fullname):
"""Load a frozen module."""
if cls.find_module(fullname) is None:
raise ImportError("{0} is not a frozen module".format(fullname))
is_reload = fullname in sys.modules
try:
return imp.init_frozen(fullname)
except:
if not is_reload and fullname in sys.modules:
del sys.modules[fullname]
raise
def chained_path_hook(*path_hooks):
"""Create a closure which sequentially checks path hooks to see which ones
(if any) can work with a path."""
def path_hook(entry):
"""Check to see if 'entry' matches any of the enclosed path hooks."""
finders = []
for hook in path_hooks:
try:
finder = hook(entry)
except ImportError:
continue
else:
finders.append(finder)
if not finders:
raise ImportError("no finder found")
else:
return ChainedFinder(*finders)
return path_hook
class ChainedFinder:
"""Finder that sequentially calls other finders."""
def __init__(self, *finders):
self._finders = finders
def find_module(self, fullname, path=None):
for finder in self._finders:
result = finder.find_module(fullname, path)
if result:
return result
else:
return None
def check_name(method):
"""Decorator to verify that the module being requested matches the one the
loader can handle.
The first argument (self) must define _name which the second argument is
comapred against. If the comparison fails then ImportError is raised.
"""
def inner(self, name, *args, **kwargs):
if self._name != name:
raise ImportError("loader cannot handle %s" % name)
return method(self, name, *args, **kwargs)
wrap(inner, method)
return inner
class _ExtensionFileLoader:
"""Loader for extension modules.
The constructor is designed to work with FileFinder.
"""
def __init__(self, name, path, is_pkg):
"""Initialize the loader.
If is_pkg is True then an exception is raised as extension modules
cannot be the __init__ module for an extension module.
"""
self._name = name
self._path = path
if is_pkg:
raise ValueError("extension modules cannot be packages")
@check_name
@set_package
def load_module(self, fullname):
"""Load an extension module."""
is_reload = fullname in sys.modules
try:
module = imp.load_dynamic(fullname, self._path)
module.__loader__ = self
return module
except:
if not is_reload and fullname in sys.modules:
del sys.modules[fullname]
raise
@check_name
def is_package(self, fullname):
"""Return False as an extension module can never be a package."""
return False
@check_name
def get_code(self, fullname):
"""Return None as an extension module cannot create a code object."""
return None
@check_name
def get_source(self, fullname):
"""Return None as extension modules have no source code."""
return None
def suffix_list(suffix_type):
"""Return a list of file suffixes based on the imp file type."""
return [suffix[0] for suffix in imp.get_suffixes()
if suffix[2] == suffix_type]
def module_for_loader(fxn):
"""Decorator to handle selecting the proper module for loaders.
Decorated modules are passed the module to use instead of the module name.
The module is either from sys.modules if it already exists (for reloading)
or is a new module which has __name__ set. If any exception is raised by
the decorated method and the decorator added a module to sys.modules, then
the module is deleted from sys.modules.
The decorator assumes that the decorated method takes self/cls as a first
argument and the module as the second argument.
"""
def decorated(self, fullname):
module = sys.modules.get(fullname)
is_reload = bool(module)
if not is_reload:
# This must be done before open() is called as the 'io' module
# implicitly imports 'locale' and would otherwise trigger an
# infinite loop.
module = imp.new_module(fullname)
sys.modules[fullname] = module
try:
return fxn(self, module)
except:
if not is_reload:
del sys.modules[fullname]
raise
wrap(decorated, fxn)
return decorated
class PyLoader:
"""Loader base class for Python source.
Requires implementing the optional PEP 302 protocols as well as
source_path.
"""
@module_for_loader
def load_module(self, module):
"""Load a source module."""
return _load_module(module)
def _load_module(self, module):
"""Initialize a module from source."""
name = module.__name__
source_path = self.source_path(name)
code_object = self.get_code(module.__name__)
if not hasattr(module, '__file__'):
module.__file__ = source_path
if self.is_package(name):
module.__path__ = [module.__file__.rsplit(path_sep, 1)[0]]
module.__package__ = module.__name__
if not hasattr(module, '__path__'):
module.__package__ = module.__package__.rpartition('.')[0]
exec(code_object, module.__dict__)
return module
def get_code(self, fullname):
"""Get a code object from source."""
source_path = self.source_path(fullname)
source = self.get_data(source_path)
# Convert to universal newlines.
line_endings = b'\n'
for index, c in enumerate(source):
if c == ord(b'\n'):
break
elif c == ord(b'\r'):
line_endings = b'\r'
try:
if source[index+1] == ord(b'\n'):
line_endings += b'\n'
except IndexError:
pass
break
if line_endings != b'\n':
source = source.replace(line_endings, b'\n')
return compile(source, source_path, 'exec', dont_inherit=True)
class PyPycLoader(PyLoader):
"""Loader base class for Python source and bytecode.
Requires implementing the methods needed for PyLoader as well as
source_mtime, bytecode_path, and write_bytecode.
"""
@module_for_loader
def load_module(self, module):
"""Load a module from source or bytecode."""
name = module.__name__
source_path = self.source_path(name)
bytecode_path = self.bytecode_path(name)
module.__file__ = source_path if source_path else bytecode_path
return self._load_module(module)
def get_code(self, fullname):
"""Get a code object from source or bytecode."""
# XXX Care enough to make sure this call does not happen if the magic
# number is bad?
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)
magic = data[:4]
pyc_timestamp = marshal._r_long(data[4:8])
bytecode = data[8:]
try:
# Verify that the magic number is valid.
if imp.get_magic() != magic:
raise ImportError("bad magic number")
# 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")
except ImportError:
# 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.
# XXX If the bytecode is ill-formed, would it be beneficial to
# try for using source if available and issue a warning?
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))
# Use the source.
code_object = super().get_code(fullname)
# Generate bytecode and write it out.
if not sys.dont_write_bytecode:
data = bytearray(imp.get_magic())
data.extend(marshal._w_long(source_timestamp))
data.extend(marshal.dumps(code_object))
self.write_bytecode(fullname, data)
return code_object
class PyFileLoader(PyLoader):
"""Load a Python source file."""
def __init__(self, name, path, is_pkg):
self._name = name
self._is_pkg = is_pkg
# Figure out the base path based on whether it was source or bytecode
# that was found.
try:
self._base_path = _path_without_ext(path, imp.PY_SOURCE)
except ValueError:
self._base_path = _path_without_ext(path, imp.PY_COMPILED)
def _find_path(self, ext_type):
"""Find a path from the base path and the specified extension type that
exists, returning None if one is not found."""
for suffix in suffix_list(ext_type):
path = self._base_path + suffix
if _path_exists(path):
return path
else:
return None
@check_name
def source_path(self, fullname):
"""Return the path to an existing source file for the module, or None
if one cannot be found."""
# Not a property so that it is easy to override.
return self._find_path(imp.PY_SOURCE)
@check_name
def get_source(self, fullname):
"""Return the source for the module as a string.
Return None if the source is not available. Raise ImportError if the
laoder cannot handle the specified module.
"""
source_path = self._source_path(name)
if source_path is None:
return None
import tokenize
with closing(_io.FileIO(source_path, 'r')) as file: # Assuming bytes.
encoding, lines = tokenize.detect_encoding(file.readline)
# XXX Will fail when passed to compile() if the encoding is
# anything other than UTF-8.
return open(source_path, encoding=encoding).read()
def get_data(self, path):
"""Return the data from path as raw bytes."""
return _io.FileIO(path, 'r').read() # Assuming bytes.
@check_name
def is_package(self, fullname):
"""Return a boolean based on whether the module is a package.
Raises ImportError (like get_source) if the loader cannot handle the
package.
"""
return self._is_pkg
class PyPycFileLoader(PyPycLoader, PyFileLoader):
"""Load a module from a source or bytecode file."""
@check_name
def source_mtime(self, name):
"""Return the modification time of the source for the specified
module."""
source_path = self.source_path(name)
if not source_path:
return None
return int(_os.stat(source_path).st_mtime)
@check_name
def bytecode_path(self, fullname):
"""Return the path to a bytecode file, or None if one does not
exist."""
# Not a property for easy overriding.
return self._find_path(imp.PY_COMPILED)
@check_name
def write_bytecode(self, name, data):
"""Write out 'data' for the specified module, returning a boolean
signifying if the write-out actually occurred.
Raises ImportError (just like get_source) if the specified module
cannot be handled by the loader.
"""
bytecode_path = self.bytecode_path(name)
if not bytecode_path:
bytecode_path = self._base_path + suffix_list(imp.PY_COMPILED)[0]
file = _io.FileIO(bytecode_path, 'w') # Assuming bytes.
try:
with closing(file) as bytecode_file:
bytecode_file.write(data)
return True
except IOError as exc:
if exc.errno == errno.EACCES:
return False
else:
raise
class FileFinder:
"""Base class for file finders.
Subclasses are expected to define the following attributes:
* _suffixes
Sequence of file suffixes whose order will be followed.
* _possible_package
True if importer should check for packages.
* _loader
A callable that takes the module name, a file path, and whether
the path points to a package and returns a loader for the module
found at that path.
"""
def __init__(self, path_entry):
"""Initialize an importer for the passed-in sys.path entry (which is
assumed to have already been verified as an existing directory).
Can be used as an entry on sys.path_hook.
"""
absolute_path = _path_absolute(path_entry)
if not _path_isdir(absolute_path):
raise ImportError("only directories are supported")
self._path_entry = absolute_path
def find_module(self, fullname, path=None):
tail_module = fullname.rpartition('.')[2]
package_directory = None
if self._possible_package:
for ext in self._suffixes:
package_directory = _path_join(self._path_entry, tail_module)
init_filename = '__init__' + ext
package_init = _path_join(package_directory, init_filename)
if (_path_isfile(package_init) and
_case_ok(self._path_entry, tail_module) and
_case_ok(package_directory, init_filename)):
return self._loader(fullname, package_init, True)
for ext in self._suffixes:
file_name = tail_module + ext
file_path = _path_join(self._path_entry, file_name)
if (_path_isfile(file_path) and
_case_ok(self._path_entry, file_name)):
return self._loader(fullname, file_path, False)
else:
# Raise a warning if it matches a directory w/o an __init__ file.
if (package_directory is not None and
_path_isdir(package_directory) and
_case_ok(self._path_entry, tail_module)):
_warnings.warn("Not importing directory %s: missing __init__"
% package_directory, ImportWarning)
return None
class ExtensionFileFinder(FileFinder):
"""Importer for extension files."""
_possible_package = False
_loader = _ExtensionFileLoader
def __init__(self, path_entry):
# Assigning to _suffixes here instead of at the class level because
# imp is not imported at the time of class creation.
self._suffixes = suffix_list(imp.C_EXTENSION)
super().__init__(path_entry)
class PyFileFinder(FileFinder):
"""Importer for source/bytecode files."""
_possible_package = True
_loader = PyFileLoader
def __init__(self, path_entry):
# Lack of imp during class creation means _suffixes is set here.
# Make sure that Python source files are listed first! Needed for an
# optimization by the loader.
self._suffixes = suffix_list(imp.PY_SOURCE)
super().__init__(path_entry)
class PyPycFileFinder(PyFileFinder):
"""Finder for source and bytecode files."""
_loader = PyPycFileLoader
def __init__(self, path_entry):
super().__init__(path_entry)
self._suffixes += suffix_list(imp.PY_COMPILED)
class PathFinder:
"""Meta path finder for sys.(path|path_hooks|path_importer_cache)."""
@classmethod
def _path_hooks(cls, path, hooks=None):
"""Search sequence of hooks for a finder for 'path'.
If 'hooks' is false then use sys.path_hooks.
"""
if not hooks:
hooks = sys.path_hooks
for hook in hooks:
try:
return hook(path)
except ImportError:
continue
else:
raise ImportError("no path hook found for {0}".format(path))
@classmethod
def _path_importer_cache(cls, path, default=None):
"""Get the finder for the path from sys.path_importer_cache.
If the path is not in the cache, find the appropriate finder and cache
it. If None is cached, get the default finder and cache that
(if applicable).
Because of NullImporter, some finder should be returned. The only
explicit fail case is if None is cached but the path cannot be used for
the default hook, for which ImportError is raised.
"""
try:
finder = sys.path_importer_cache[path]
except KeyError:
finder = cls._path_hooks(path)
sys.path_importer_cache[path] = finder
else:
if finder is None and default:
# Raises ImportError on failure.
finder = default(path)
sys.path_importer_cache[path] = finder
return finder
@classmethod
def find_module(cls, fullname, path=None):
"""Find the module on sys.path or 'path'."""
if not path:
path = sys.path
for entry in path:
try:
finder = cls._path_importer_cache(entry)
except ImportError:
continue
loader = finder.find_module(fullname)
if loader:
return loader
else:
return None
_DEFAULT_PATH_HOOK = chained_path_hook(ExtensionFileFinder, PyPycFileFinder)
class _DefaultPathFinder(PathFinder):
"""Subclass of PathFinder that implements implicit semantics for
__import__."""
@classmethod
def _path_hooks(cls, path):
"""Search sys.path_hooks as well as implicit path hooks."""
try:
return super()._path_hooks(path)
except ImportError:
implicit_hooks = [_DEFAULT_PATH_HOOK, imp.NullImporter]
return super()._path_hooks(path, implicit_hooks)
@classmethod
def _path_importer_cache(cls, path):
"""Use the default path hook when None is stored in
sys.path_importer_cache."""
return super()._path_importer_cache(path, _DEFAULT_PATH_HOOK)
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()
_IMPLICIT_META_PATH = [BuiltinImporter, FrozenImporter, _DefaultPathFinder]
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 settting __package__ if
the loader did not.
"""
if package:
if not hasattr(package, 'rindex'):
raise ValueError("__package__ not set to a string")
elif package not in sys.modules:
msg = ("Parent module {0!r} not loaded, cannot perform relative "
"import")
raise SystemError(msg.format(package))
if not name and level == 0:
raise ValueError("Empty module name")
if level > 0:
dot = len(package)
for x in range(level, 1, -1):
try:
dot = package.rindex('.', 0, dot)
except ValueError:
raise ValueError("attempted relative import beyond "
"top-level package")
if name:
name = "{0}.{1}".format(package[:dot], name)
else:
name = package[:dot]
with ImportLockContext():
try:
return sys.modules[name]
except KeyError:
pass
parent = name.rpartition('.')[0]
path = None
if parent:
if parent not in sys.modules:
_gcd_import(parent)
# Backwards-compatibility; be nicer to skip the dict lookup.
parent_module = sys.modules[parent]
path = parent_module.__path__
meta_path = sys.meta_path + _IMPLICIT_META_PATH
for finder in meta_path:
loader = finder.find_module(name, path)
if loader is not None:
loader.load_module(name)
break
else:
raise ImportError("No module named {0}".format(name))
# Backwards-compatibility; be nicer to skip the dict lookup.
module = sys.modules[name]
if parent:
# Set the module as an attribute on its parent.
setattr(parent_module, name.rpartition('.')[2], module)
# Set __package__ if the loader did not.
if not hasattr(module, '__package__') or module.__package__ is None:
# Watch out for what comes out of sys.modules to not be a module,
# e.g. an int.
try:
module.__package__ = module.__name__
if not hasattr(module, '__path__'):
module.__package__ = module.__package__.rpartition('.')[0]
except AttributeError:
pass
return module
def _import(name, globals={}, locals={}, fromlist=[], level=0):
"""Import a module.
The 'globals' argument is used to infer where the import is occuring 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:
# __package__ is not guaranteed to be defined.
try:
package = globals['__package__']
except KeyError:
package = globals['__name__']
if '__path__' not in globals:
package = package.rpartition('.')[0]
module = _gcd_import(name, package, level)
# The hell that is fromlist ...
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 sys.modules[name.partition('.')[0]]
elif not name:
return module
else:
cut_off = len(name) - len(name.partition('.')[0])
return sys.modules[module.__name__[:-cut_off]]
else:
# If a package was imported, try to import stuff from fromlist.
if hasattr(module, '__path__'):
if '*' in fromlist and hasattr(module, '__all__'):
fromlist.remove('*')
fromlist.extend(module.__all__)
for x in (y for y in fromlist if not hasattr(module,y)):
try:
_gcd_import('{0}.{1}'.format(module.__name__, x))
except ImportError:
pass
return module
# XXX Eventually replace with a proper __all__ value (i.e., don't expose os
# replacements but do expose _ExtensionFileLoader, etc. for testing).
__all__ = [obj for obj in globals().keys() if not obj.startswith('__')]
