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Issue #14605: Make explicit the entries on sys.path_hooks that used to 

be implicit.

Added a warning for when sys.path_hooks is found to be empty. Also
changed the meaning of None in sys.path_importer_cache to represent
trying sys.path_hooks again (an interpretation of previous semantics).
Also added a warning for when None was found.

The long-term goal is for None in sys.path_importer_cache to represent
the same as imp.NullImporter: no finder found for that sys.path entry.
This commit is contained in:
Brett Cannon 2012-04-25 20:54:04 -04:00
parent 8f79dd5d7c
commit e0d88a173c
9 changed files with 3075 additions and 3206 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

64
Lib/importlib/_bootstrap.py
View File

@ -752,15 +752,15 @@ class PathFinder:
"""Meta path finder for sys.(path|path_hooks|path_importer_cache)."""
@classmethod
def _path_hooks(cls, path, hooks=None):
def _path_hooks(cls, path):
"""Search sequence of hooks for a finder for 'path'.
If 'hooks' is false then use sys.path_hooks.
"""
if hooks is None:
hooks = sys.path_hooks
for hook in hooks:
if not sys.path_hooks:
_warnings.warn('sys.path_hooks is empty', ImportWarning)
for hook in sys.path_hooks:
try:
return hook(path)
except ImportError:
@ -770,14 +770,11 @@ class PathFinder:
path=path)
@classmethod
def _path_importer_cache(cls, path, default=None):
def _path_importer_cache(cls, path):
"""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
it. 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.
@ -790,9 +787,13 @@ class PathFinder:
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)
if finder is None:
msg = ("'None' in sys.path_importer_cache[{!r}], so retrying "
"finder search; in future versions of Python 'None' "
"will represent no finder".format(path))
_warnings.warn(msg, ImportWarning)
del sys.path_importer_cache[path]
finder = cls._path_hooks(path)
sys.path_importer_cache[path] = finder
return finder
@ -931,29 +932,6 @@ class FileFinder:
# Import itself ###############################################################
_DEFAULT_PATH_HOOK = None # Set in _setup()
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."""
@ -1008,7 +986,7 @@ def _sanity_check(name, package, level):
raise ValueError("Empty module name")
_IMPLICIT_META_PATH = [BuiltinImporter, FrozenImporter, _DefaultPathFinder]
_IMPLICIT_META_PATH = [BuiltinImporter, FrozenImporter, PathFinder]
_ERR_MSG = 'No module named {!r}'
@ -1203,12 +1181,6 @@ def _setup(sys_module, _imp_module):
if builtin_os == 'nt':
SOURCE_SUFFIXES.append('.pyw')
supported_loaders = [(ExtensionFileLoader, _suffix_list(3), False),
(SourceFileLoader, _suffix_list(1), True),
(SourcelessFileLoader, _suffix_list(2), True)]
setattr(self_module, '_DEFAULT_PATH_HOOK',
FileFinder.path_hook(*supported_loaders))
def _install(sys_module, _imp_module):
"""Install importlib as the implementation of import.
@ -1218,6 +1190,8 @@ def _install(sys_module, _imp_module):
"""
_setup(sys_module, _imp_module)
orig_import = builtins.__import__
builtins.__import__ = __import__
builtins.__original_import__ = orig_import
supported_loaders = [(ExtensionFileLoader, _suffix_list(3), False),
(SourceFileLoader, _suffix_list(1), True),
(SourcelessFileLoader, _suffix_list(2), True)]
sys.path_hooks.extend([FileFinder.path_hook(*supported_loaders),
_imp.NullImporter])

4
Lib/importlib/test/import_/test_fromlist.py
View File

@ -1,6 +1,7 @@
"""Test that the semantics relating to the 'fromlist' argument are correct."""
from .. import util
from . import util as import_util
import imp
import unittest
class ReturnValue(unittest.TestCase):
@ -73,7 +74,8 @@ class HandlingFromlist(unittest.TestCase):
def test_no_module_from_package(self):
# [no module]
with util.mock_modules('pkg.__init__') as importer:
with util.import_state(meta_path=[importer]):
with util.import_state(meta_path=[importer],
path_hooks=[imp.NullImporter]):
module = import_util.import_('pkg', fromlist='non_existent')
self.assertEqual(module.__name__, 'pkg')
self.assertTrue(not hasattr(module, 'non_existent'))

82
Lib/importlib/test/import_/test_path.py
View File

@ -9,6 +9,7 @@ import tempfile
from test import support
from types import MethodType
import unittest
import warnings
class FinderTests(unittest.TestCase):
@ -64,12 +65,18 @@ class FinderTests(unittest.TestCase):
self.assertTrue(path in sys.path_importer_cache)
self.assertTrue(sys.path_importer_cache[path] is importer)
def test_path_importer_cache_has_None(self):
# Test that if sys.path_importer_cache has None that None is returned.
clear_cache = {path: None for path in sys.path}
with util.import_state(path_importer_cache=clear_cache):
for name in ('asynchat', 'sys', '<test module>'):
self.assertTrue(machinery.PathFinder.find_module(name) is None)
def test_empty_path_hooks(self):
# Test that if sys.path_hooks is empty a warning is raised and
# PathFinder returns None.
# tried again (with a warning).
with util.import_state(path_importer_cache={}, path_hooks=[],
path=['bogus_path']):
with warnings.catch_warnings(record=True) as w:
warnings.simplefilter('always')
self.assertIsNone(machinery.PathFinder.find_module('os'))
self.assertNotIn('os', sys.path_importer_cache)
self.assertEqual(len(w), 1)
self.assertTrue(issubclass(w[-1].category, ImportWarning))
def test_path_importer_cache_has_None_continues(self):
# Test that having None in sys.path_importer_cache causes the search to
@ -78,9 +85,16 @@ class FinderTests(unittest.TestCase):
module = '<test module>'
importer = util.mock_modules(module)
with util.import_state(path=['1', '2'],
path_importer_cache={'1': None, '2': importer}):
loader = machinery.PathFinder.find_module(module)
self.assertTrue(loader is importer)
path_importer_cache={'1': None, '2': importer},
path_hooks=[imp.NullImporter]):
with warnings.catch_warnings(record=True) as w:
warnings.simplefilter('always')
loader = machinery.PathFinder.find_module(module)
self.assertTrue(loader is importer)
self.assertEqual(len(w), 1)
warned = w[0]
self.assertTrue(issubclass(warned.category, ImportWarning))
self.assertIn(repr(None), str(warned.message))
def test_path_importer_cache_empty_string(self):
# The empty string should create a finder using the cwd.
@ -94,57 +108,9 @@ class FinderTests(unittest.TestCase):
self.assertIn(os.curdir, sys.path_importer_cache)
class DefaultPathFinderTests(unittest.TestCase):
"""Test _bootstrap._DefaultPathFinder."""
def test_implicit_hooks(self):
# Test that the implicit path hooks are used.
bad_path = '<path>'
module = '<module>'
assert not os.path.exists(bad_path)
existing_path = tempfile.mkdtemp()
try:
with util.import_state():
nothing = _bootstrap._DefaultPathFinder.find_module(module,
path=[existing_path])
self.assertTrue(nothing is None)
self.assertTrue(existing_path in sys.path_importer_cache)
result = isinstance(sys.path_importer_cache[existing_path],
imp.NullImporter)
self.assertFalse(result)
nothing = _bootstrap._DefaultPathFinder.find_module(module,
path=[bad_path])
self.assertTrue(nothing is None)
self.assertTrue(bad_path in sys.path_importer_cache)
self.assertTrue(isinstance(sys.path_importer_cache[bad_path],
imp.NullImporter))
finally:
os.rmdir(existing_path)
def test_path_importer_cache_has_None(self):
# Test that the default hook is used when sys.path_importer_cache
# contains None for a path.
module = '<test module>'
importer = util.mock_modules(module)
path = '<test path>'
# XXX Not blackbox.
original_hook = _bootstrap._DEFAULT_PATH_HOOK
mock_hook = import_util.mock_path_hook(path, importer=importer)
_bootstrap._DEFAULT_PATH_HOOK = mock_hook
try:
with util.import_state(path_importer_cache={path: None}):
loader = _bootstrap._DefaultPathFinder.find_module(module,
path=[path])
self.assertTrue(loader is importer)
finally:
_bootstrap._DEFAULT_PATH_HOOK = original_hook
def test_main():
from test.support import run_unittest
run_unittest(FinderTests, DefaultPathFinderTests)
run_unittest(FinderTests)
if __name__ == '__main__':
test_main()

13
Lib/pkgutil.py
View File

@ -379,18 +379,15 @@ def get_importer(path_item):
for path_hook in sys.path_hooks:
try:
importer = path_hook(path_item)
sys.path_importer_cache.setdefault(path_item, importer)
break
except ImportError:
pass
else:
importer = None
sys.path_importer_cache.setdefault(path_item, importer)
if importer is None:
try:
importer = ImpImporter(path_item)
except ImportError:
importer = None
try:
importer = ImpImporter(path_item)
except ImportError:
importer = None
return importer

12
Lib/runpy.py
View File

@ -9,6 +9,7 @@ importers when locating support scripts as well as when importing modules.
# Written by Nick Coghlan <ncoghlan at gmail.com>
# to implement PEP 338 (Executing Modules as Scripts)
import os
import sys
import imp
from pkgutil import read_code
@ -94,7 +95,7 @@ def _get_filename(loader, mod_name):
for attr in ("get_filename", "_get_filename"):
meth = getattr(loader, attr, None)
if meth is not None:
return meth(mod_name)
return os.path.abspath(meth(mod_name))
return None
# Helper to get the loader, code and filename for a module
@ -198,10 +199,6 @@ def _get_importer(path_name):
try:
importer = cache[path_name]
except KeyError:
# Not yet cached. Flag as using the
# standard machinery until we finish
# checking the hooks
cache[path_name] = None
for hook in sys.path_hooks:
try:
importer = hook(path_name)
@ -213,10 +210,7 @@ def _get_importer(path_name):
# NullImporter throws ImportError if the supplied path is a
# *valid* directory entry (and hence able to be handled
# by the standard import machinery)
try:
importer = imp.NullImporter(path_name)
except ImportError:
return None
importer = imp.NullImporter(path_name)
cache[path_name] = importer
return importer

15
Lib/test/test_cmd_line_script.py
View File

@ -1,5 +1,6 @@
# tests command line execution of scripts
import importlib
import unittest
import sys
import os
@ -49,12 +50,16 @@ print('cwd==%a' % os.getcwd())
"""
def _make_test_script(script_dir, script_basename, source=test_source):
return make_script(script_dir, script_basename, source)
to_return = make_script(script_dir, script_basename, source)
importlib.invalidate_caches()
return to_return
def _make_test_zip_pkg(zip_dir, zip_basename, pkg_name, script_basename,
source=test_source, depth=1):
return make_zip_pkg(zip_dir, zip_basename, pkg_name, script_basename,
source, depth)
to_return = make_zip_pkg(zip_dir, zip_basename, pkg_name, script_basename,
source, depth)
importlib.invalidate_caches()
return to_return
# There's no easy way to pass the script directory in to get
# -m to work (avoiding that is the whole point of making
@ -72,7 +77,9 @@ def _make_launch_script(script_dir, script_basename, module_name, path=None):
else:
path = repr(path)
source = launch_source % (path, module_name)
return make_script(script_dir, script_basename, source)
to_return = make_script(script_dir, script_basename, source)
importlib.invalidate_caches()
return to_return
class CmdLineTest(unittest.TestCase):
def _check_output(self, script_name, exit_code, data,

5
Misc/NEWS
View File

@ -10,6 +10,11 @@ What's New in Python 3.3.0 Alpha 3?
Core and Builtins
-----------------
- Issue #14605: No longer have implicit entries in sys.path_hooks. If
sys.path_hooks is found to be empty, a warning will be raised. If None is
found in sys.path_importer_cache, a warning is raised and a search on
sys.path_hooks is attempted.
- Issue #13903: Implement PEP 412. Individual dictionary instances can now share
their keys with other dictionaries. Classes take advantage of this to share
their instance dictionary keys for improved memory and performance.

6084
Python/importlib.h
View File

File diff suppressed because it is too large Load Diff

2
Python/pythonrun.c
View File

@ -229,7 +229,7 @@ import_init(PyInterpreterState *interp, PyObject *sysmod)
Py_FatalError("Py_Initialize: can't save _imp to sys.modules");
}
value = PyObject_CallMethod(importlib, "_setup", "OO", sysmod, impmod);
value = PyObject_CallMethod(importlib, "_install", "OO", sysmod, impmod);
if (value == NULL) {
PyErr_Print();
Py_FatalError("Py_Initialize: importlib install failed");