Historically, -m added the empty string as sys.path
zero, meaning it resolved imports against the current
working directory, the same way -c and the interactive
prompt do.
This changes the sys.path initialisation to add the
*starting* working directory as sys.path[0] instead,
such that changes to the working directory while the
program is running will have no effect on imports
when using the -m switch.
(cherry picked from commit d5d9e02dd3)
Previously AttributeError was raised, but that's not very reflective of the fact that the requested module can't be found since the specified parent isn't actually a package.
Directory and zipfile execution previously added
the parent directory of the directory or zipfile
as sys.path[0] and then subsequently overwrote
it with the directory or zipfile itself.
This caused problems in isolated mode, as it
overwrote the "stdlib as a zip archive" entry
in sys.path, as the parent directory was
never added.
The attempted fix to that issue in bpo-29319
created the opposite problem in *non*-isolated
mode, by potentially leaving the parent
directory on sys.path instead of overwriting it.
This change fixes the root cause of the problem
by removing the whole "add-and-overwrite" dance
for sys.path[0], and instead simply never adds
the parent directory to sys.path in the first
place.
Issue #26100:
* Add subprocess._optim_args_from_interpreter_flags()
* Add test.support.optim_args_from_interpreter_flags()
* Use new functions in distutils, test_cmd_line_script, test_compileall and
test_inspect
The change enables test_details() test of test_inspect when -O or -OO command
line option is used.
The previous fix only handled the case of the parent package of __main__
failing to initialize.
Also make the "Error while finding spec" formatting slightly more appealing,
and document and test that the module name must be absolute.
Initialize package before calling find_spec() for __main__, so that we do not
incorrectly handle exceptions from __init__.py. When runpy is used from the
Python CLI, use an internal exception rather than ImportError, to avoid
catching unexpected exceptions.
Also remove exception message rewriting in _run_module_as_main(), because it
seems to be redundant with the _get_main_module_details() function.
Note that __spec__.name is not currently guaranteed to be in
sys.modules when the code is running, only __name__ is.
The "running module is in sys.modules" invariant will be
expanded to also cover __spec__.name in a subsequent patch.
