Commit d2e7b338 authored by Brett Cannon's avatar Brett Cannon

Implement the more specific PEP 302 semantics for loaders and what happens upon

load failure in relation to reloads. Also expose
importlib.util.module_for_loader to handle all of the details of this along
with making sure all current loaders behave nicely.
parent 0586ed62
No related merge requests found
......@@ -151,3 +151,36 @@ find and load modules.
searched for a finder for the path entry and, if found, is stored in
:data:`sys.path_importer_cache` along with being queried about the
module.
:mod:`importlib.util` -- Utility code for importers
---------------------------------------------------
.. module:: importlib.util
:synopsis: Importers and path hooks
This module contains the various objects that help in the construction of
an :term:`importer`.
.. function:: module_for_loader(method)
A :term:`decorator` for a :term:`loader` which handles selecting the proper
module object to load with. The decorated method is expected to have a call
signature of ``method(self, module_object)`` for which the second argument
will be the module object to be used (note that the decorator will not work
on static methods because of the assumption of two arguments).
The decorated method will take in the name of the module to be loaded as
normal. If the module is not found in :data:`sys.modules` then a new one is
constructed with its :attr:`__name__` attribute set. Otherwise the module
found in :data:`sys.modules` will be passed into the method. If an
exception is raised by the decorated method and a module was added to
:data:`sys.modules` it will be removed to prevent a partially initialized
module from being in left in :data:`sys.modules` If an exception is raised
by the decorated method and a module was added to :data:`sys.modules` it
will be removed to prevent a partially initialized module from being in
left in :data:`sys.modules`. If the module was already in
:data:`sys.modules` then it is left alone.
Use of this decorator handles all the details of what module a loader
should use as specified by :pep:`302`.
to do
/////
* Change failed loading based on PEP 302 changes.
* Refactor source/bytecode finder/loader code such that bytecode support is a
subclass of source support (makes it nicer for VMs that don't use CPython
bytecode).
* Implement PEP 302 protocol for loaders (should just be a matter of testing).
+ Built-in.
+ Frozen.
+ Extension.
+ Source/bytecode.
* Public API left to expose (w/ docs!)
+ abc
+ abc
- Finder
- Finder
* find_module
* find_module
- Loader
- Loader
* load_module
* load_module
- (?) Importer(Finder, Loader)
- ResourceLoader(Loader)
- (?) Importer(Finder, Loader)
* get_data
- ResourceLoader(Loader)
- InspectLoader(Loader)
* get_data
* is_package
* get_code
* get_source
- InspectLoader(Loader)
- (?) SourceLoader(ResourceLoader)
* is_package
* get_code
* get_source
* source_path
* bytecode_path
* write_bytecode (not abstract)
- (?) SourceLoader(ResourceLoader)
+ util
* source_path
* bytecode_path
* write_bytecode (not abstract)
- set___package__ decorator
+ util
+ machinery
- get_module decorator (rename: module_for_loader)
- set___package__ decorator
- (?) Chained path hook/finder
- Extensions importers
+ machinery
* ExtensionFinder
* (?) Loader
- (?) Chained path hook/finder
- Extensions importers
- Source/bytecode importers
* ExtensionFinder
* (?) Loader
* SourceFinder
* (?) Loader
- Source/bytecode importers
+ test
* SourceFinder
* (?) Loader
- abc
- PathFinder
* FinderTests [doc]
* LoaderTests [doc]
* Make sure that there is documentation *somewhere* fully explaining the
semantics of import that can be referenced from the package's documentation
......
......@@ -136,8 +136,13 @@ class BuiltinImporter:
"""Load a built-in module."""
if fullname not in sys.builtin_module_names:
raise ImportError("{0} is not a built-in module".format(fullname))
module = imp.init_builtin(fullname)
return module
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:
......@@ -160,8 +165,13 @@ class FrozenImporter:
"""Load a frozen module."""
if cls.find_module(fullname) is None:
raise ImportError("{0} is not a frozen module".format(fullname))
module = imp.init_frozen(fullname)
return module
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
class ChainedImporter(object):
......@@ -249,14 +259,13 @@ class _ExtensionFileLoader(object):
@set___package__
def load_module(self, fullname):
"""Load an extension module."""
assert self._name == fullname
is_reload = fullname in sys.modules
try:
module = imp.load_dynamic(fullname, self._path)
module.__loader__ = self
return module
except:
# If an error occurred, don't leave a partially initialized module.
if fullname in sys.modules:
if not is_reload and fullname in sys.modules:
del sys.modules[fullname]
raise
......@@ -282,16 +291,17 @@ def suffix_list(suffix_type):
if suffix[2] == suffix_type]
# XXX Need a better name.
def get_module(fxn):
"""Decorator to handle selecting the proper module for load_module
implementations.
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 then __loader__, __name__, __file__, and __path__ are
all restored on the module to their original values.
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):
......@@ -302,27 +312,12 @@ def get_module(fxn):
# implicitly imports 'locale' and would otherwise trigger an
# infinite loop.
module = imp.new_module(fullname)
module.__name__ = fullname
sys.modules[fullname] = module
else:
original_values = {}
modified_attrs = ['__loader__', '__name__', '__file__', '__path__']
for attr in modified_attrs:
try:
original_values[attr] = getattr(module, attr)
except AttributeError:
pass
try:
return fxn(self, module)
except:
if not is_reload:
del sys.modules[fullname]
else:
for attr in modified_attrs:
if attr in original_values:
setattr(module, attr, original_values[attr])
elif hasattr(module, attr):
delattr(module, attr)
raise
wrap(decorated, fxn)
return decorated
......@@ -375,7 +370,7 @@ class _PyFileLoader(object):
return self._find_path(imp.PY_COMPILED)
@check_name
@get_module
@module_for_loader
def load_module(self, module):
"""Load a Python source or bytecode module."""
name = module.__name__
......
from importlib import util
from . import util as test_util
import imp
import sys
import types
import unittest
class ModuleForLoaderTests(unittest.TestCase):
"""Tests for importlib.util.module_for_loader."""
def return_module(self, name):
fxn = util.module_for_loader(lambda self, module: module)
return fxn(self, name)
def raise_exception(self, name):
def to_wrap(self, module):
raise ImportError
fxn = util.module_for_loader(to_wrap)
try:
fxn(self, name)
except ImportError:
pass
def test_new_module(self):
# Test that when no module exists in sys.modules a new module is
# created.
module_name = 'a.b.c'
with test_util.uncache(module_name):
module = self.return_module(module_name)
self.assert_(module_name in sys.modules)
self.assert_(isinstance(module, types.ModuleType))
self.assertEqual(module.__name__, module_name)
def test_reload(self):
# Test that a module is reused if already in sys.modules.
name = 'a.b.c'
module = imp.new_module('a.b.c')
with test_util.uncache(name):
sys.modules[name] = module
returned_module = self.return_module(name)
self.assert_(sys.modules[name] is returned_module)
def test_new_module_failure(self):
# Test that a module is removed from sys.modules if added but an
# exception is raised.
name = 'a.b.c'
with test_util.uncache(name):
self.raise_exception(name)
self.assert_(name not in sys.modules)
def test_reload_failure(self):
# Test that a failure on reload leaves the module in-place.
name = 'a.b.c'
module = imp.new_module(name)
with test_util.uncache(name):
sys.modules[name] = module
self.raise_exception(name)
self.assert_(sys.modules[name] is module)
def test_main():
from test import support
support.run_unittest(ModuleForLoaderTests)
if __name__ == '__main__':
test_main()
"""Utility code for constructing importers, etc."""
from ._bootstrap import module_for_loader
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment