importlib.util._find_spec_from_path('__main__') fails

[terryjreedy]

Bug report

Module pyclbr cannot browse a file named __main__ because it cannot get the spec.

>>> from importlib import util
>>> util._find_spec_from_path('__init__')
ModuleSpec(name='__init__', loader=<_frozen_importlib_external.SourceFileLoader object at 0x000001C6C2462DB0>, origin='C:\\Programs\\Python313\\Lib\\idlelib\\__init__.py')
>>> util._find_spec_from_path('__main__')
Traceback (most recent call last):
  File "<pyshell#14>", line 1, in <module>
    util._find_spec_from_path('__main__')
  File "<frozen importlib.util>", line 67, in _find_spec_from_path
ValueError: __main__.__spec__ is None

This is 3.13.0a5 but same in prior versions.

[Xiaokang2022]

FYI, according to https://docs.python.org/3/reference/import.html#main-spec, __main__.__spec__ is None in the some cases, which should be a possible cause of the problem.

For #117743, perhaps changing the way IDLE is started can solve this problem.

[Xiaokang2022]

perhaps changing the way IDLE is started can solve this problem.

FYI, on the Windows system, we changed the launch command of the shortcut to launch IDLE to the following:

\Python313\pythonw.exe -m idlelib

The preceding of Python313 in the path above does not need to be changed, and is omitted here.

At this point, running IDLE with this shortcut won't raise exception about pyclbr. This change is imperceptible to the user. I don't know if there are any other consequences of doing so, but it does solve the above problem on Windows.

[terryjreedy]

The current icon 'target' is C:\Programs\Python314\pythonw.exe "C:\Programs\Python314\Lib\idlelib\idle.pyw. I presume you are suggesting changing to end with -m idlelib. After reading the linked doc, I see why.

But I don't think this will properly resolve the issue, which is that find_spec treats __main__ as a reserved module name, whereas as pyclbr needs to read the users .../__main__.py, which a user may be editing, not idlelib/__main__.py, which usually will be a different file. I need to sleep, but I wonder if pyclbr really needs to use find_spec, especially if the file is being edited.