Python now supports checking bytecode cache up-to-dateness with a hash of the
source contents rather than volatile source metadata. See the PEP for details.
While a fairly straightforward idea, quite a lot of code had to be modified due
to the pervasiveness of pyc implementation details in the codebase. Changes in
this commit include:
- The core changes to importlib to understand how to read, validate, and
regenerate hash-based pycs.
- Support for generating hash-based pycs in py_compile and compileall.
- Modifications to our siphash implementation to support passing a custom
key. We then expose it to importlib through _imp.
- Updates to all places in the interpreter, standard library, and tests that
manually generate or parse pyc files to grok the new format.
- Support in the interpreter command line code for long options like
--check-hash-based-pycs.
- Tests and documentation for all of the above.
old methods now provide implementations when PEP 451 APIs are present.
This should help with backwards-compatibility with code which has not
been updated to work with PEP 451.
importlib.abc.Loader.init_module_attrs() and implement
importlib.abc.InspectLoader.load_module().
The importlib.abc.Loader.init_module_attrs() method sets the various
attributes on the module being loaded. It is done unconditionally to
support reloading. Typically people used
importlib.util.module_for_loader, but since that's a decorator there
was no way to override it's actions, so init_module_attrs() came into
existence to allow for overriding. This is also why module_for_loader
is now pending deprecation (having its other use replaced by
importlib.util.module_to_load).
All of this allowed for importlib.abc.InspectLoader.load_module() to
be implemented. At this point you can now implement a loader with
nothing more than get_code() (which only requires get_source();
package support requires is_package()). Thanks to init_module_attrs()
the implementation of load_module() is basically a context manager
containing 2 methods calls, a call to exec(), and a return statement.
While the previous location was fine, it makes more sense to have the
method higher up in the inheritance chain, especially at a point where
get_source() is defined which is the earliest source_to_code() could
programmatically be used in the inheritance tree in importlib.abc.
the default exception/value when called instead of raising/returning
NotimplementedError/NotImplemented (except where appropriate).
This should allow for the ABCs to act as the bottom/end of the MRO with expected
default results.
As part of this work, also make importlib.abc.Loader.module_repr()
optional instead of an abstractmethod.
state of the import system. Also make importlib.invalidate_caches()
work with sys.meta_path instead of sys.path_importer_cache to
completely separate the path-based import system from the overall
import system.
Patch by Eric Snow.
Brett Cannon
Benjamin Peterson
Serhiy Storchaka
Matthias Bussonnier
Eric Snow
Brett Cannon
Andrew Svetlov
Nick Coghlan