Python's help utility crashes when collections.abc module is asked.

[taaaf11]

Bug report

Bug description:

I am running Python 3.13.0-b2 on Debian 12 i386. When collections.abc is entered into python interactive help utility, the interpreter crashes.

>>> help
>>> collections.abc
(Python interpreter crashes)

The traceback is indented. So I am attaching video.

recording.mp4

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-123339: fix out-of-bounds values in inspect.findsource #123347
• gh-123339: Fix cases of inconsistency of __module__ and __firstlineno__ in classes #123613
• [3.13] gh-123339: Fix cases of inconsistency of __module__ and __firstlineno__ in classes (GH-123613) #124735

[picnixz]

It appears that lines, lnum = findsource(object) returns objects with len(lines) < lnum. It appears that:

    if isclass(object):
        try:
            firstlineno = vars(object)['__firstlineno__']
        except (TypeError, KeyError):
            raise OSError('source code not available')
        return lines, firstlineno - 1

and I assume that firstlineno is too large for lines. There is a check if lnum >= len(lines) but only for non-class objects. I can prepare a patch (and it seems it fixes the issue).

[serhiy-storchaka]

Why these classes have the wrong value at first place? I suspect there is a different issue behind this, and clipping the line number can just sweep it under cover.

[picnixz]

The issue is likely due to the fact that _collections_abc has it's name set to collections.abc (#123347 (comment))

[serhiy-storchaka]

This is a severe issue. Modules collections.abc and decimal are affected completely, because their content is defined in other files. But several other classes in other modules, like abc.ABCMeta or tomllib.TOMLDecodeError are affected too.

For collections.abc and decimal the solution can be replacing these modules completely in sys.modules This allows to get sources of classes in these modules (previously this did not work). For other classes with changed __module__ the only solution is to delete __firstlineno__. Since this issue can affect not only the stdlib classes, it is better to do this on the low level: setting __module__ will delete __firstlineno__.

[picnixz]

I'll work on something now. I'm done with what I wanted to do today.

[picnixz]

Ok, I've tried to simply change the type.__module__ setter but it appears it's not sufficient enough. I have the idea but I don't have the time today. So I'll do it tomorrow.

[serhiy-storchaka]

I already had a ready solution, just was not able to create a PR due to a power outage.