Use sys.modules.get() in the "with _ModuleLockManager(name):" block
to protect the dictionary key with the module lock and use an atomic
get to prevent race condition.
Remove also _bootstrap._POPULATE since it was unused
(_bootstrap_external now has its own _POPULATE object), add a new
_SENTINEL object instead.
* Rewrite importlib _get_module_lock(): it is now responsible to hold
the imp lock directly.
* _find_and_load() now holds the module lock to check if name is in
sys.modules to prevent a race condition
PEP 432 specifies a number of large changes to interpreter startup code, including exposing a cleaner C-API. The major changes depend on a number of smaller changes. This patch includes all those smaller changes.
Issue #26637: The importlib module now emits an ImportError rather than a
TypeError if __import__() is tried during the Python shutdown process but
sys.path is already cleared (set to None).
In a previous change, __spec__.parent was prioritized over
__package__. That is a backwards-compatibility break, but we do
eventually want __spec__ to be the ground truth for module details. So
this change reverts the change in semantics and instead raises an
ImportWarning when __package__ != __spec__.parent to give people time
to adjust to using spec objects.
not defined for a relative import.
This is the start of work to try and clean up import semantics to rely
more on a module's spec than on the myriad attributes that get set on
a module. Thanks to Rose Ames for the patch.
Known limitations of the current implementation:
- documentation changes are incomplete
- there's a reference leak I haven't tracked down yet
The leak is most visible by running:
./python -m test -R3:3 test_importlib
However, you can also see it by running:
./python -X showrefcount
Importing the array or _testmultiphase modules, and
then deleting them from both sys.modules and the local
namespace shows significant increases in the total
number of active references each cycle. By contrast,
with _testcapi (which continues to use single-phase
initialisation) the global refcounts stabilise after
a couple of cycles.
